Geology 1 – Physical Geology

Lessons, Activities, and Labs David Bazard and Emily Wright College of the Redwoods

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Contents Lesson One: Introduction ...... 1 Worksheet 1.1 ...... 1 Lesson Two: Plate Tectonics ...... 3 Worksheet 2.1: Earth Layers ...... 3 Worksheet 2.2 Plate Boundaries ...... 4 Worksheet 2.3: Plate Boundary Table ...... 7 Lab 2.4: Using GPS to Study Plate Tectonics ...... 8 Lab 2.5: Using magnetic properties of rocks to investigate plate motions ...... 15 Lesson Three: Minerals ...... 21 Background Reading Part I: Basic Chemistry of Rock Forming Minerals ...... 21 Worksheet 3.1: Basic Chemistry of Minerals ...... 24 Background Reading Part II: Mineral Identification ...... 25 Lab 3.2: Known Minerals ...... 27 Lab 3.3: Unknowns ...... 28 Lab 3.4: Special Minerals ...... 29 Lesson Four: Igneous Rocks ...... 31 Background Reading: Igneous Rocks ...... 31 Worksheet 4.1: Igneous Rocks ...... 35 Lab 4.2: Igneous Knowns ...... 38 Lab 4.3: Igneous Rock Unknowns ...... 39 Igneous Rock Lab Quiz – Review Sheet ...... 41 Lesson Five: Volcanoes ...... 43 Background Reading: Volcanoes ...... 43 Worksheet 5.1: Volcanoes ...... 46 Lesson Six: Weathering and Sedimentary Rocks ...... 49 Background Reading: Sedimentary Processes ...... 49 Worksheet 6.1: Sediment ...... 54 Lab 6.2: Analyzing Sediment...... 57 Lab 6.3: Sedimentary Knowns ...... 58 Lab 6.4: Sedimentary Unknowns: ...... 59 Lesson Seven: Metamorphic Rocks ...... 61 Background Reading: Metamorphic Rocks ...... 61

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Worksheet 7.1: Metamorphic Rocks ...... 66 Lab 7.2: Metamorphic Minerals and Known Metamorphic Rocks ...... 69 Lab 7.3: Unknown Metamorphic Rocks: ...... 70 Sedimentary and Metamorphic Rock Lab Quiz - Study Guide ...... 72 Lesson Eight: Structural Geology ...... 75 Background Reading: Structural Geology ...... 75 Worksheet 8.1: Moonstone Beach Field Trip Preparation ...... 79 Worksheet 8.2: Geologic Structures ...... 83 Lab 8.3: Geologic Maps ...... 85 Lesson Nine: Geologic Time ...... 91 Background Reading: Geologic Time ...... 91 Worksheet 9.1: Relative Time...... 94 Worksheet 9.2 -Absolute Time ...... 95 Worksheet 9.3: Geologic Time Scale ...... 97 Lab 9.4: Geologic Map of California ...... 98 Lesson Ten: Landscape Evolution ...... 99 Background Reading: Topographic Maps ...... 99 Background Reading: Landforms ...... 100 Worksheet 10.1 - Mass Movement...... 103 Worksheet 10.2 - Rivers ...... 104 Worksheet 10.3 Landscapes ...... 105 Lab 10.4: Topographic Maps...... 106 Lab 10.5 Maps of Landscapes ...... 107

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

Lesson One: Introduction

Worksheet 1.1 Read the discussion below. This discussion is similar to any paragraph that you might select at random from an introductory geology textbook. When you are reading about science, you might find yourself focusing on facts that have been discovered. It is important to learn these facts to understand what scientists know about how the world works, but to really appreciate science you must also appreciate that science is the process by which people discover these facts. The questions below will help guide you thinking about the science that you read in terms of the scientific process.

Discussion: (1)Geologists tell us that the explosiveness of a volcanic eruption is related to the amount of a material called silica that is in the magma (liquid rock) of a volcano. Silica is made of the elements silicon and oxygen and is the same material found in a mineral called quartz. (2)This conclusion is based on looking at the most explosive volcanic eruptions and finding that they produce quartz rich volcanic rocks. (3)Also, scientists have found, through lab and field studies, that magma with a higher silica content is “thicker “ (more viscous) than magma with a lower silica content. This is similar to how honey is “thicker” than water. (4)Geologists have used this information to come up with the idea that higher silica content makes lava thicker, and thicker magma can hold gas under higher pressure. (5)When high pressure gas comes to the surface it erupts more explosively than gas trapped in a “thinner” (less viscous) liquid. The same process occurs when oatmeal boils. When the bubbles in oatmeal “pop”, they explode and create a bigger mess than a pan of boiling water.

1. Assign each numbered sentence to one of the following categories Observations/Data: Things that have been directly observed or measured by the researchers. They must be repeatable, meaning the observation can be made either multiple times or was observed by multiple groups of people.

Interpretations: The simplest explanation that fits all of the data and observations. An interpretation is always subject to change based on new observations.

2. State the overall hypothesis of the discussion above.

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3. Write a brief description of a lab experiment that would test this hypothesis.

4. Write a brief description of a field study that would test this hypothesis.

5. Choose one of your studies above and make a testable prediction about the outcome of the study. Example of a Testable Prediction: Hypothesis: The hill between the College of the Redwoods parking lot and the central part of the main campus was formed by the movement of a fault. Prediction: A trench dug across the uphill edge of the College of the Redwoods main parking lot would reveal soil and sediment layers that have been offset vertically.

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Lesson Two: Plate Tectonics

Worksheet 2.1: Earth Layers 1. On the left part of the diagram below, label the following layers: inner core, outer core, lower mantle, upper mantle, oceanic crust, continental crust. 2. On the right part (the blow up) of the diagram draw a line representing the base of the lithosphere, then shade in and label the area that is part of the lithosphere. 3. On the bottom of the left diagram, add an arrow pointing to the Mohrovicic Discontinuity and label it “Moho”.

Figure: Emily Wright, 2017

4. Assume the lithosphere is 100km thick. Assume the earth has a radius of 6370 km. Determine the radius of the classroom globe and use a comparison (ratio) to determine how thick the lithosphere would be on this globe to represent a scale model of the actual earth (show your work).

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Worksheet 2.2 Plate Boundaries 1. The flow chart below will help you organize your thinking about Plate Tectonics and Plate Boundaries. This may be slightly different than the way that the concepts were organized in your textbook. Complete the chart by filling in the missing words.

Plate Tectonics

Plate Boundaries

Convergent

Mid Ocean Ridge

Ocean to Ocean Convergence

2. Sketch a Cross Section View of the Mid Atlantic Ridge. Include the continents South America and Africa in your sketch. Your sketch will not be accurately scaled, but make sure that you include: a. The Mid Ocean Ridge (MOR) b. Arrows in the tectonic plates showing the direction of plate motion c. Oceanic Crust d. Continental Crust e. Lithosphere f. Arrows in the Mantle showing convection g. Area of Partial Melt (where the magma is made)

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods 3. Sketch a Cross Section View of the Cascadia Subduction Zone. Your drawing should include: a. Arrows in the tectonic plates showing the direction of plate motion b. Oceanic Lithosphere* c. Continental Lithosphere* d. Mantle (the non-lithospheric mantle) e. Area of partial melt (where the magma is made) f. Trench g. Volcanic Arc Mountain Range *You can leave out the crust and the Moho to make this drawing a little cleaner.

4. Sketch a Map View of the Hawaiian Hot Spot Island Chain. Your drawing should include: a. An arrow showing the direction of plate motion b. An active volcanic island c. Older volcanic islands d. Seamounts

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5. Consider the three plates (ABC) shown in the figure below (Figure: David Bazard, 2012). The boundaries are shown by standard map symbols. The arrows show relative plate motion. These may vary on the same plate because they show the relative motion between two plates at a single location, not the absolute plate motion. Note: This is a hypothetical situation, not California (although some parts are very similar). For each numbered location (1-5) provide:  The type of stress expected Location #1  The name of this type of plate boundary Stress:

B Plate Boundary: A Location #2 Stress:

Plate Boundary:

Location #3 Stress:

Plate Boundary:

Location #4 Stress: C Plate Boundary:

Location #5 Stress:

Plate Boundary:

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Worksheet 2.3: Plate Boundary Table Complete the following table.

Boundary Type Sense of relative motion Map Symbol Principal Stress Important Features Earthquakes Volcanoes Faults C Transform Transform Shear Offset markers Yes No

Subduction Zone

Continental Collision

Mid Ocean Ridge

Continental Rift

Hot Spot N/A N/A N/A

7 Lab 2.4: Using GPS to Study Plate Tectonics (public domain text and figures from UNAVCO) UNAVCO is a non-profit membership-governed university consortium that facilitates geoscience research and education using geodesy. In the US, UNAVCO operates the Plate Boundary Observatory (PBO) as the geodetic component of the US EarthScope program.

The global positioning system (GPS) is a fleet of 29 satellites that are orbiting our planet approximately 11,000 miles above Earth’s surface. A position can be calculated using at least three satellites. High precision GPS can calculate a position to the nearest millimeter (hand- held units only get down to about 1 meter).

When deformation occurs a point on Earth’s surface changes. The position change can be measured using high-precision GPS instruments. Earth scientists use these data to record how much and how quickly Earth’s crust is changing because of plate tectonics and to better understand the underlying processes of the deformation. Each station continuously records its position. A plot of the station's changes in position is called a time series. Each station has time series for north-south, east-west and up-down motions. Southward or westward motions are shown as either negative north (for south) or negative east (for west).

The photograph shows a high precision GPS station (P162) located on Table Bluff, near the CR campus. The time series plot on the next page shows the position change recorded in millimeters (mm). The changes are relative to a Stable North America Reference Frame -SNARF (the interior portion of the North American plate). For a color photo and unpdated data search “UNAVCO P162”.

The following figure shows how to interpret the time series plots. Complete the bottom right portion of the figure.

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

9 Questions: 1. In what general direction has this site been moving in the last twelve years?

2. Is it moving up or down?

3. By January 2017, how far north had P162 moved since it’s installation in 2005?

4. An average how much does P162 move northward per year? Your answer should have the units mm/yr (millimeters per year).

5. Multiple choice: The units mm/yr express a measure of ______. a. Distance b. Time c. Velocity (speed) d. Volume

6. Calculate the eastward velocity of P162 using the same method that you used for the northward velocity.

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods 7. A vector is an arrow that shows both direction and a magnitude. In this case the magnitude is the velocity. Use the plot below to plot the appropriate vector. There is an example on page 13 help guide you.

You might be interested in knowing the total horizontal velocity of the GPS station and the precise direction that it is moving. You can determine these things either graphically or algebraically. The algebraic solutions will be more accurate (if done properly) but require some math background. You may choose the method that is most appropriate for you.

8. Determine the total horizontal velocity of P162. Choose one of the two methods and indicate the method you used. a. Graphical method: measure the length of the vector (diagonal line) that you have drawn on your plot using the scale of the graph paper. b. Algebraic method: Use the Pythagorean Theorem to calculate the length of the vector (the hypotenuse). Hint: It is important to remember order of operations

11 9. Determine the precise direction in azimuth. (Azimuth is a method of reading a compass as a 360-degree circle where North is 0°, East is 90°, South is 180° and West is 270°. a. Graphical method: extend your vector onto the circle in the diagram and read the number on the circle. (See page 13 for example). b. The algebraic method is more advanced this time. You will need some trigonometric relationships (think: “soh cah toa” …if that means nothing to you, stick to the graphical method)

10. Draw the appropriate vector for P162 on the map below. To get the right length arrow, estimate based on the 25 mm/yr reference arrow in the lower left corner. Work in pencil first, then when you are confident, ink in your final arrow.

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

Example Vector Plot: Station C Moves: 3 mm/yr North and 6 mm/yr East

Step 1: Polt the North and East Vectors Recall that negative velocities will be South or West

Step 2: Plot the Final Vector Trace a horizontal line from the head of the North and a verical line from the head of the East vector, then draw a new vector with the tail at the center of the plot and the head at the intersection point of your two lines. This is your final vector.

Step 3: Find the azimuth direction for the vector Extend the arrow to the circle and read the azimuth direction.

Station C is moving 66° with a velocity of 6.7 mm/yr

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11. The map below shows the motions of several southern California GPS stations. Describe how Barstow is moving relative to Los Angles. In other words, if you were in Los Angles, Barstow would appear to be moving ______.

Examples of Half Arrows:

USGS Public Domain

12. Using the information from the previous question, add half-arrows along the San Andreas Fault (SAF) in the map above, that show the relative sense of motion. (See the example on the right)

The map at right shows average GPS position movements relative to the stable interior of the North American plate. Each vector shows the direction of motion of a point on the crust. Vector length indicates speed in mm/year.

13. Use the information you learned above to approximate the location of the SAF. Draw in the plate boundary on the map.

14. What other interesting patterns do you notice in the GPS veolicities?

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Lab 2.5: Using magnetic properties of rocks to investigate plate motions

When rocks form they can acquire and record the current state of the Earth’s magnetic field at the location of their formation. Minerals of igneous rocks align with the prevailing magnetic field to produce a record of the magnetic field orientation at the time of crystallization. We think of the current magnetic field orientation as Normal. This means there is a magnetic attraction toward the north magnetic pole (near the north geographic pole) and a magnetic repulsion away from the south magnetic pole. An iron- rich igneous rock forming today would record a normal orientation.

(USGS Public Domain) At various times in the past the orientation has been reversed. A rock crystallizing at this time would have a magnetism pointed toward the south magnetic pole. The magnetic time scale below provides a record of when the Earth’s magnetic field was either normal (black bars) or reversed (white bars). Each time period is given an anomaly number. The age is shown in millions of years (Ma).

(USGS, Public Domain)

15 The map on page 19 shows magnetic anomalies that have been mapped in the Atlantic Ocean. The numbered lines repesent the numbered anomalies in the timescale on page 15. For example, the line with the number 8 represents oceanic crust that was formed during anomaly 8, about 27 million year ago. Confirm that you can find this age using the chart. There is an anomogy 8 line on either side of the Mid Atlantic Ridge, but the lines are not straight. They have been offset by transfrom fault zones such as the Bode Verde Fault Zone. Find two places where the Bode Verde F.Z. offsets anomaly 8.

In the following exercise you will use the pattern of magnetic lineations (anomalies) to restore the positions of Africa and South America at the time the magnetic anomaly was being formed on the Mid-Atlantic Ridge.

1. We will use anomaly number 21 for this exercise. Use the magnetic reversal time scale on page 15 to determine the age of magnetic anomaly 21.

2. Use the figure on page 19 and these instructions to complete this section.

First: draw a colored line over each of the magnetic lineations of anomaly number 21 on the South American side of the Mid-Atlantic Ridge (do not color the African side). Connect the anomaly lines by also drawing over the transform boundaries that separate the anomaly 21 lineations.

Second: Place a piece of tracing paper over the figure and hold it in place with tape or paper clips. Repeat the process described above for anomaly 21 on the African side of the Mid-Atlantic Ridge. Note that anomaly 21 should be colored on the figure only for the South American side and it should be colored on the tracing paper only for the African side.

Third: With the tracing paper in place, trace the coastlines of Africa and South America on the tracing paper with black pencil. Also use a black pencil to trace the boundaries of the figure (the box) and the 20 degree South latitude line.

Fourth: Detach the tracing paper and slide it toward the South American side until the colored line on the tracing paper matches the colored line on the figure. When the two lines are matched as closely as possible, hold the tracing paper in place and trace the coastline of South America in colored pencil on the tracing paper. Also trace the 20 degree South line on the tracing paper in color.

3. The map you have constructed on the tracing paper shows the Mid-Atlantic Ridge as it existed when magnetic anomaly 21 was being formed. Your tracing paper also shows the relative positions of segments of the coastlines of Africa and South America as they were at the time of anomaly 21.

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods 4. What is the evidence that the movement of the plates from magnetic anomaly 21 time to present was not strictly in an east-west direction?

5. We will now determine the rate at which the Atlantic Ocean is growing. In other words, the speed at which Africa is moving away from South America. a. At the northern most end of the Mid Atlantic Ridge that is pictured, how far has anomaly 21 moved from the ridge? (Use the bar scale on the map)

b. Have both sides moved the same amount? If not, how much has the other side moved?

c. How much has the width of the ocean increased in this location since anomaly 21 formed?

d. Now use this answer and your answer from question 1 to determine the rate that the Atlantic Ocean is spreading. In this case the rate is a velocity. You will recall that Speed = Distance/Time. Express your answer in the units km/Ma (Ma = millions of years ago).

e. Convert your answer to mm/yr. Show your work.

6. Compare your answer to the previous question to the speeds (velocities) that you worked with in Worksheet 2.1. Does your answer seem reasonable for the speed of tectonic plates? If not, why might that be

7. Is the southern end of the Mid Atlantic Ridge spreading at the same rate as the northern end or is it faster or slower? How can you tell?

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

Lesson Three: Minerals Background Reading Part I: Basic Chemistry of Rock Forming Minerals Minerals are defined as having a definable chemical composition. For example, the mineral quartz always has the composition of SiO2. This means it is made of building blocks that include one silicon atom linked to two oxygen atoms. You can think of these as Lego blocks that are all the same. A single crystal may have millions of these blocks all stacked together to make the crystal that you hold in your hand. To understand minerals, we must understand what we mean by an element (such as silicon or oxygen), and how the presence of certain elements and their linking together (bonding) influences the mineral properties such as hardness, color, density, ability to cleave, and crystalline form. In addition, it is important to recognize that although minerals have a definable chemistry, they can appear different due to a slight impurity added to the mineral chemistry. For example, amethyst (beautiful purple colored mineral) is really just quartz. However, a small amount of iron has been added to the SiO2chemistry. It may help to think of these impurities as being like a drop of food coloring added to an ice cube. The ice is still basically H2O, but adding food coloring can result in green ice, even though the coloring represents less than 1% of the composition of the ice cube. Likewise, Rose Quartz takes its color from impurities of titanium within the crystal.

Here are some basic aspects of chemistry we need to understand minerals:

Element: a substance that cannot be decomposed into simpler substances by ordinary processes. There are 92 naturally occurring elements. The atom is the smallest particle that exists as an element.

Common Elements in the crust: Oxygen (O), Silicon (Si), Aluminum (Al), Iron (Fe), Magnesium (Mg), Calcium (Ca), Potassium (K), Sodium (Na)

The table below lists the common elements found in the crust.

Negative Anion Positive Cation Si4+ Al3+ O2- Fe3+ Mg2+ Fe2+

Na1+ Ca2+ K1+

Note that the elements listed in the table above are listed as either negative or positive ions (Anion or Cations).

What is an ion? Ions: An atom or molecule that possesses an electrical charge. This is due to an atom gaining or losing an electron. Cations (positive charge, lost electrons), Anions (negative charge, gained electrons)

21 In order to understand why ions form, we need to understand the basic structure of an atom. Atoms are composed of a nucleus with neutrons and protons and a surrounding electron cloud. The neutrons have no charge, the protons have a positive charge, and the electrons have a negative charge. The positive and negative charges attract so the protons attract the negative charge of the electron cloud.

(Public Domain image – Google public domain images)

The number of protons in the atom’s nucleus defines the element. So, for example, Oxygen shows up on the periodic table as 8, because it has 8 protons in its nucleus. Silicon (Si) has 14 protons and it is listed as number 14 on the periodic table.

Ideally, there is a balance between the number of protons and electrons to make the total charge of the atom zero. Thus you might predict that Oxygen would have 8 protons and 8 electrons. This would be +8 and –8. Add these together and you get zero. However, there is a “tendency” of some atoms to gain or lose electrons. Oxygen has a tendency to gain two electrons. When this happens it then has +8 (protons) and –10 (electrons). This causes the total charge to be –2, (because +8 –10 = -2). This tendency is represented on the table of common elements presented above as O2- . When an atom has a negative charge, like oxygen, we call it an Anion.

So, here’s the tricky part – what made oxygen an anion? Was it the gaining of electrons or the loss of electrons? If you say gaining electrons, you are correct. This means that a gain of electrons makes an ion negative. Do you see why this can be confusing? It is a gain of something (negative electrons) that makes the atom negative, or an anion.

Following this same pattern, if an atom loses electrons (which are negative), the atom becomes more positive. If the atom has a positive charge it is called a Cation.

A way to remember that cations are positive (and anions are negative) is to remember that the word “cation” has the letter “t” and that the “t” looks like a plus sign. Also the prefix “a” or “an” means “not” or negative. If something is “atypical” it is not typical. Thus, an anion is negative.

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Notice that most of the common elements in the earth’s crust are cations (Silicon, Iron, Potassium, Calcium, Sodium, Aluminum, Magnesium). Oxygen is the only common anion in the table above.

Why do we care about ions? Since positive and negative charges attract, anion and cations will attract and form compounds. These are building blocks of minerals. Look again at the table of common elements in the earth’s crust. Notice that there is only one anion in this table. That means that this particular anion (oxygen) has to be involved in a lot of the “gluing together” of ions to form minerals. For this reason, Oxygen is the most common element in the Earth’s crust. It seems strange, but when you are walking across a rocky field, beach, or mountain top, you are walking mostly on oxygen!

We call the process of ions “gluing together” – Bonding. Two common types of atomic bonds are ionic and covalent bonding.

A bond that forms due to the exchange of electrons between a positive cation and a negative anion is called an Ionic Bond. The key word in this definition is exchange. Ionic bonding is due to an exchange of electrons. Common table salt (sodium chloride) is formed due to ionic bonding of Na+ and Cl- An ionic bond tends to be weaker than a covalent bond. Thus, salt is not very hard.

Bounding that involves the sharing of electrons is called Covalent Bond. In this case one electron actually occupies the outer electron cloud of two atoms at once (yes, this is strange) and provides the added negative charge to pull the two atoms together. The key word in this definition is sharing. Covalent bonding is due to the sharing of electrons. Diamonds are covalently bonded carbon atoms. A covalent bond tends to be stronger than an ionic bond. Thus, diamond is very hard.

Why do we care about bonding? Bonding determines mineral composition. Bonding explains properties: hardness, cleavage, color, crystalline structure Bonding explains tendency to change: oxidation, leaching of elements.

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Worksheet 3.1: Basic Chemistry of Minerals 1. Silicon (Si) has a tendency to lose 4 electrons. This results is a charge of _____ 2. Oxygen (O) has a tendency to gain 2 electrons. This results is a charge of _____ 3. Which one of the two ions described above is considered a cation? ______

4. Use your answers from 1 and 2 to determine the charge of SiO4. Assume the charges you listed as the answers as the charges for each atom in the molecule SiO4. Remember SiO4 consists of one silicon atom and four oxygen atoms, so you will need to add up the total charge for one silicon atom and four oxygen.

5. How many Magnesium ions does the SiO4 ion need to bond with to provide a neutral charge? The charge for Magnesium results from losing two electrons. This is the formula for the mineral Olivine (gem quality olivine is called peridot)

6. A common way for minerals to form is through the cooling (or freezing) of magma. Do you think all minerals form from in this manner? If not, think of an example of another way a mineral could form.

7. Quartz (SiO2) is a very common mineral but large well-formed crystals, like the one pictured at right are relatively rare. Describe a possible scenario in which a well-formed crystal like this one could form.

Pixabay Pubic Domain

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Background Reading Part II: Mineral Identification Goals: Our goal in this lab is to become familiar with common physical properties of rock forming minerals and learn some basic techniques of mineral identification.

Background: Each mineral is characterized by a specific chemistry and internal structure. As a result, all specimens of a particular mineral will possess diagnostic physical properties. The physical properties of minerals we will investigate are: Cleavage, Hardness, Color, Density, Luster, and Reaction to Hydrochloric Acid. Other properties you might consider are Crystal Form, Taste, Magnetism, Streak, and Optical Properties.

You will only be responsible for the following common rock forming minerals on the lab exam: Quartz, Potassium Feldspar, Plagioclase Feldspar (light and dark), Muscovite, Biotite, Amphibole (Hornblende), Pyroxene (Augite), Olivine, Calcite, Halite, Gypsum, Galena, and Pyrite.

The following includes some additional information that will help with understanding the differences and similarities of these minerals. Remember we are focusing on some of the most common minerals found in the earth’s crust (other than galena).

Quartz.  Quartz can occur as either visible crystals or as aggregates of very small crystals.  Quartz often endures the earth’s erosive processes because it is hard and lacks cleavage. This hardness allows it to be polished (by nature or rock tumblers) and is one of the reason it is often used as a gemstone.  Small impurities of other elements can give quartz different colors, bands, or patterns.  Much of the cryptocrystalline quartz (agate, chert, etc.) forms when silicon dioxide crystallizes (precipitates) from groundwater.

Feldspar. Feldspars are a very common mineral in igneous rocks. However, their excellent cleavage and chemistry cause them to easily weather to clays. Therefore they are not as common away from their source areas (such as large granite outcrops) as quartz.  Feldspar is a mineral group that includes Potassium Feldspar and Plagioclase Feldspars.  The Plagioclase Feldspars are a subgroup of feldspars that range from light-colored Albite (sodium-rich) to dark-colored Anorthite (calcium-rich).  Plagioclase can sometimes be distinguished from the Potassium Feldspars by the existence of striations (fine parallel grooves on the mineral surface).

Micas- This includes both Muscovite and Biotite that have similar hardness and cleavage

Amphibole and Pyroxene – These are both dark minerals with similar hardness. The cleavages on these minerals can be difficult to determine, but amphibole does not have 90 degree cleavages and Pyroxene does have 90 degree cleavages. This can be used to distinguish the two.

Aggregates – some of our specimens occur as aggregates of very small crystals (olivine and pyrite). Consequently it may be difficult to determine hardness and cleavage for these specimens.

25 Moh’s Scale of Hardness Moh’s Scale and Minerals Hardness of Common Objects 10 – Diamond 9 – Corundum 8 – Topaz 7 – Quartz 6.5- Streak Plate 6 – K-Feldspar (orthoclase) 5 – Apatite 5. 5 – Glass, Knife Blade 4 – Fluorite 4.5 – wire, iron nail 3 – Calcite 3.5 – penny 2 – Gypsum 2.5 - fingernail 1 - Talc

Fracture and Cleavage – light reflection

Fracture – light is scattered Perfect Cleavage – flat Multiple Cleavage surfaces by irregular surfaces surface reflects all light in reflect light in the same the same direction direction to produce a “flash” when the specimen is turned in the light

Number of Cleavages Description Diagram 0 Irregular Masses without shiney surfaces

1 Basal - “books” split apart along the base

2 @90 Prisms – rectancular sections

2 not @90 Prisms without right angles

3 @ 90 Cubic

3 not @ 90 Rhombic Cleavage – look like skewed cubes

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

Lab 3.2: Known Minerals Task: Investigate the lab specimens to complete the mineral property chart below and indicate the most diagnostic properties for each mineral. Mineral Properties Name Silicate or Hardness Cleavage (number Color Other: Unique Density, Streak, Acid Nonsilicate and angles); or Reaction, Metallic Luster Fracture Quartz

Muscovite

Biotite

K-Feldspar (Orthoclase)

Na-Plagioclase Feldspar

Ca-Plagioclase Feldspar

Amphibole (variety Hornblende) Pyroxene (variety Augite) Olivine

Calcite

Gypsum

Halite

Pyrite

Galena

27 Lab 3.3: Unknowns Identify the unknown mineral samples and state the distinguishing properties that were most helpful to you in identifying the mineral.

Specimen Mineral Name Key Properties

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

Identify the minerals present in the provided rock samples: Rock 1 Rock 2 Rock 3 Rock 4 Rock 5

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Lab 3.4: Special Minerals Investigate at least two of the “Additional Minerals” provided. DO NOT scratch these minerals or apply acid. Please treat them gently. You can use the reference material provided to answer the questions.

For each mineral indicate: 1. Describe the mineral color and other visual appearances 2. Describe the mineral shape (e.g., bladed, cubic, columns, hexagonal, etc) Use the references to answer the following: 3. Hardness and specific gravity (or density), distinguishing features 4. List the formula for the mineral 5. Indicate if the mineral is a silicate or a non-silicate. 6. If it is a non-silicate, indicate the specific mineral class (e.g., oxide, halide, etc.) 7. Briefly describe the environment of formation

Mineral: Mineral:

1 1

2 2

3 3

4 4

5 5

6 6

7 7

29 Minerals Quiz Review Sheet

Examples of Questions:

 Describe the distinguishing properties of the mineral in this aggregate

 List the mineral name

 Describe, as completely as possible, the cleavage of this mineral

 Describe the hardness of this mineral (this is not a mineral we saw in the lab)

 List a property that allows you to distinguish this mineral from others we have examined in the lab.

 List two of the minerals present in this rock

 List the hardness of this mineral

You are responsible for the following mineral properties: Color Streak Hardness Cleavage Planes and Angles (or fracture) Acid Reaction Density Distinguishing Properties (how you tell this mineral from one that may be similar)

You are responsible for identifying the following minerals: Quartz, Muscovite, Biotite, Potassium Feldspar, Sodium Plagioclase Feldspar, Calcium Plagioclase Feldspar, Amphibole (hornblende), Pyroxene (augite/hypersthene), Olivine Calcite, Halite, Gypsum, Pyrite, Galena

Notes: You can use one side of 8.5x11 paper with your own notes – typed or hand written. NOT ALLOWED:  Any of the tables or charts in this lab book unless you type or write it onto a new sheet.  Photocopies or scans of the lab, book, or another student’s work]  Photographs of minerals  Consulting experts or other students during the exam

Photographs of our lab samples are available using the following link: http://tinyurl.com/g1mineral This link will also be available through Canvas. You will also have time to study the samples in the lab.

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Lesson Four: Igneous Rocks

Background Reading: Igneous Rocks Igneous Rocks: Cool (crystallize) from a magma

There are two main types of Igneous Rocks: A. Intrusive or Plutonic B. Extrusive or Volcanic

Igneous Rocks are defined by Texture and Composition I. Igneous Textures: Crystal Size Crystal size is determined by the rate of cooling. Slow cooling results in larger crystals. Fast cooling results in smaller crystals.

Glass consists of unordered ions (and is therefore not crystalline). This can be the result of either extremely fast cooling or from a high silica content that prevents ions from bonding to form a crystalline structure.

Aphanitic (fine-grained texture) – from fast cooling. Found in volcanic rocks. Phaneritic (coarse-grained texture) –from slow cooling. Found in plutonic rocks Porphyritic: Larger crystals embedded in a matrix of smaller crystals. The larger crystals are called phenocrysts. The term porphyritic is often used to describe volcanic rocks. However it is sometimes used to describe plutonic rocks if much larger crystals are embedded within a coarse-grained rock). II. Igneous Composition: Basic Subdivision of Felsic and Mafic

Felsic: rocks that include substantial amounts of feldspar (fel) and quartz (si). Felsic rocks have a composition close to granite. Felsic rocks have abundant quartz, potassium and sodium feldspars (Na-plagioclase), and muscovite, with lesser amounts of biotite, and amphibole.

Mafic: rocks include substantial amounts of Iron and Magnesium bearing minerals (MgFe=mafic). Mafic rocks have a mineral assemblage close to basalt. Mafic rocks include Calcium-rich feldspar (Ca-plagioclase), pyroxene, amphibole, and olivine (but little or no quartz).

III. Generation of Magma Rock near their melting points will melt if a) the pressure drops, or if b) volatiles (including water) are added. Water acts like salt does to ice. That is, it lowers the melting temperature of the material. Water added from plate subduction lowers the mantle rock melting temperature. This causes the mantle rock to melt, which then rises and heats crustal rocks to their melting point.

31 IV. Fractional Crystallization – the process of progressive crystal formation. This results in progressive extraction of iron, magnesium, calcium and other elements from a magma, so the remaining magma becomes more felsic (richer in silica, sodium, and potassium).

How magmas change during cooling. Bowen’s reaction series shows the crystallization temperatures for minerals. Bowen’s Reaction Series explains the sequence of crystallization from a magma, and it provides a mechanism to explain how the composition of magma changes during cooling.

Bowen’s Reaction Series A list of minerals arranged in the order of the temperature at which they crystallize (or melt).

Mafic (dark) minerals crystallize at higher temperatures than felsic (light) minerals.

If cooling is slow and required elements present, early formed minerals will react with the remaining liquid to form new minerals (lower on the list).

The final rock composition depends on the initial composition of the magma. Example: if a mafic magma cools, then olivine, pyroxene, Ca-plagioclase, and amphibole will crystallize and all the magma will be gone. If a felsic magma cools, then there may not be enough iron and magnesium to form olivine or early-formed olivine will react to eventually form amphibole.

Who cares? This tells us that we will expect to find dark minerals together and light minerals together (grouping of minerals higher and lower on the list). This explains how we can get a variety of rock types from the same initial magma (crystal settling or magma separation). This explains how we can get a less mafic magma (more felsic) by a process of mafic rocks forming and enriching the magma in more felsic material.

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

Figure Credit: Bob McPherson, used by permission

33 Clasification of major groups of igneous rocks based on mineral composition and textures

Chemical Composition Felsic (silicic) Intermediate Mafic Ultramafic Dominant Minerals Quartz Amphibole Pyroxene Olivine Potassium (K) – Feldspar Sodium (Na) – Plagioclase Calcium (Ca) - Plagioclase Pyroxene Sodium (Na) - Plagioclase Calcium (Ca) - Plagioclase Accessory Minerals Muscovite Pyroxene Amphibole Calcium (Ca) - Biotite Biotite Olivine Plagioclase Amphibole

Color/Shade Lighter color Intermediate Color Dark Color (salt and pepper)

Volcanic (Extrusive) Aphanitic or Aphanitic- Rhyolite Andesite Basalt Uncommon porphyritic textures

Plutonic (Intrusive) Phaneritic or Phaneritic- Granite Diorite Gabbro Peridotite Porphyritic textures

Glassy Textures Vesicular Glass = Pumice (light) or Scoria (dark). Compact Glass = Obsidian

Pyroclastic (Fragmental) Textures Pyroclastic Volcanic Rocks: Ashy with pumice fragments = Tuff. Large Angular Fragments = Volcanic Breccia

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Worksheet 4.1: Igneous Rocks

1. Use the diagram above to identify features that are intrusive and extrusive. Fill our the chart below with the names of the features labeled in the diagram.

Intrusive Features Extrusive Features

2. Indify the specific locations (labeled on the diagram) where large, medium and small crystals would form. Largest Crystals Medium Crystals Small Crystals

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3. (Multiple Choice) How do most intrusive igneous rocks reach the surface of the earth for geologist to study? a. They are erupted from volcanoes b. They are mined c. Millions of years of uplift and erosion of overlying material expose them at the surface d. They are found almost entirely in the deepest river canyons such as the inner gorge of the Grand Canyon where rivers have cut into the deep crust

4. Use the Bowen’s Reaction Series diagram on pg. 32 to Identify each of the following minerals as either mafic (M), felsic (F), or Intermediate (I).

Olivine_____ Muscovite ______Quartz_____ Calcium-Rich Feldspar _____ Potassium-Rich Feldspar ____ Amphibole ______Pyroxene _____ Sodium-Rich Feldspar _____ Biotite _____

5. Use the Igneous Rock Identification Chart on pg. 34 to determine the appropriate name for each of the following rock descriptions.

Description Rock Name A dark colored rock found in a lava flow

An intermediate, phaneritic rock

The volcanic equivalent of granite

A rock that contains visible crystals of quartz, potassium feldspar, sodium plagioclase feldspar and small amounts of biotite and amphibole A rock that contains some visible crystals, surrounded by a dull colored, fine grained groundmass. The abundant visible crystals (phenocrysts) can be identified as amphibole.

6. Consider a sample of basalt with large olivine crystals (phenocrysts). a. Explain how this association (basalt and larger olivine crystals) formed.

b. Explain if this association is consistent (or inconsistent) with Bowen’s Reaction Series.

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

7. Consider a solid piece of Diorite that is made of the minerals Plagioclase Feldspar, Amphibole, and small amounts of quartz, muscovite, and biotite. If you slowly heat this rock, what are the first minerals that would melt, according to Bowen’s Reaction Series?

8. The Fantastic Lava Beds in Lassen National Park are basaltic andesite to andesite in composition but contain visible crystals of quartz. Is this association consistent or inconsistent with Bowen’s Reaction Series? Explain.

9. Some of the granite in the Pikes Peak Batholith in Colorado contains a small amount of a variety of olivine. Is this association consistent or inconsistent with Bowen’s Reaction Series? Explain.

37 Lab 4.2: Igneous Knowns Complete the following chart. Determining the minerals for aphanitic rocks may not be possible. In those cases either state none observed (NO) or list the color and the nature of any phenocrysts. Color Minerals Observed Composition General Texture Special (light, med., dark) (list only those that can (Mafic, Intermediate, (Phaneritic, Aphanitic, VolcanicTextures actually be observed) Felsic) Porphyritic-Phaneritic, (Glassy, Vesicular, Porphyritic-Aphanitic) Pyroclastic) Specimen A (Granite)

Specimen B (Rhyolite)

Specimen C (Diorite)

Specimen D (Andesite)

Specimen E (Gabbro)

Specimen F (Basalt)

Specimen G (Peridotite)

Specimen H (Obsidian)

Specimen I (Pumice)

Specimen J (Scoria)

Specimen K (Tuff and/or Volcanic Breccia)

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Lab 4.3: Igneous Rock Unknowns Determine the igneous rock properties for each of the unknowns. Only list minerals you actually observed Specimen Color Minerals Observed Composition General Texture Special Rock Name (light, med., dark) (list only those that can (Mafic, (Phaneritic, Aphanitic, VolcanicTextures actually be observed) Intermediate, Porphyritic-Phaneritic, (Glassy, Vesicular, Felsic) Porphyritic-Aphanitic) Pyroclastic) A

B

C

D

E

F

G

39 Specimen Color Minerals Observed Composition General Texture Special Rock Name (light, med., dark) (list only those that can (Mafic, (Phaneritic, Aphanitic, VolcanicTextures actually be observed) Intermediate, Porphyritic-Phaneritic, (Glassy, Vesicular, Felsic) Porphyritic-Aphanitic) Pyroclastic)

H

I

J

K

L

M

N

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Igneous Rock Lab Quiz – Review Sheet You are responsible for identifying the following rocks Rhyolite Andesite Basalt Granite Diorite Gabbro Peridotite Obsidian Pumice Scoria Volcanic Breccia Volcanic Tuff You are responsible for identifying distinctive minerals in intrusive igneous rocks and phenocrysts in extrusive igneous rocks: Quartz, K-feldspar, Muscovite, Biotite, Na-Plagioclase, Ca-Plagioclase, Amphibole, Pyroxene, Olivine, and possibly one of the more common non-silicate minerals (calcite, pyrite)

You are responsible for identifying and explaining the formation of the following textures Phaneritic, Phaneritic-Porphyritic Aphanitic, Aphanitic-Porphyritic Glassy Pyroclastic Vesicular

Sample Questions  Describe (and name) one of the minerals in this rock that can be used to justify the rock name., and List the rock name

 Describe (and name) one of the visible minerals in this rock that can be used to justify the rock name.

 List the texture of this igneous texture and describe how it formed

 Both samples provided are classified as the same specific igneous rock type. Identify this rock

Notes: You can use one side of 8.5x11 paper – typed or hand written. You are not allowed to use the lab sheets and table from this packet. NOT ALLOWED:  The lab tables unless you type or write it onto a new sheet.  Photocopies or scans of the lab, book, or another student’s work.  Photographs of minerals  Consulting experts or other students during the exam

Photos of igneous rocks are available on the Canvas course page and at the following URL: http://tinyurl.com/g1igneous

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Lesson Five: Volcanoes Background Reading: Volcanoes Volcanic Terms: Silca: SiO2 – silicon dioxide. This is quartz when it crystallizes. The amount of this in the magma determines the viscosity (thickness) of the magma. Viscosity: resistance to flowing. A more viscous magma is “thicker” in the same way that honey is thicker than water. The more viscous a magma, the greater its ability to trap gas and produce an explosive eruption. If it is too viscous (like obsidian or even rhyolite magma), it may be too thick to erupt and it will form domes and plugs. Pyroclastic material: hot fragments blown out of a volcano. It can range from very small ash to much larger fragments (lapilli, bombs). Pyroclastic material can be ejected upward, or flow down a volcano (pyroclastic flow) as a extremely hot avalanche of pyroclastic debris. Stratovolcano: A large, cone-shaped volcanoes consisting of alternative layers of lava and pyroclastic material. Mt Shasta and Mt Rainier are stratovolcanoes. These volcanoes are often associated with convergent plate boundaries and explosive eruptions. Shield Volcanoes: A volcano with a broad, gentle-sloping dome formed from low viscosity basaltic lava. These volcanoes exhibit Effusive eruptions. These are not violent eruptions. Lava pours out onto the ground from a vent and spreads out over the land.

Three main types of volcanic rock types and associated volcanism: Rhylolite: highest silica content (other than obsidian); it is the most viscous of all lavas; it’s viscosity causes it to form domes or freeze while still in the volcanic vent. Andesite: intermediate silica content; its relative “thickness” (viscosity) causes gas to build up pressure within the magma and result in explosive eruptions. The flows are relatively short, but extensive pyroclastic material can be produced. Andesitie volcanism can form stratovolcanoes. Basalt: low silica content; it is the least viscous of the lavas and consequently it tends to create large flows and less explosive eruptions. This ability to flow also results in shield volcanoes with low-sloping sides due to the runoff of lava. The flows can cool to produce columnar jointing and the more fluid lava will cool to form a ropey appearance (pahoehoe lava).

Plate Settings and Volcanism Divergent Boundary: typically divergent boundaries are sites of basaltic volcanism. This is true of the oceanic ridges. Pillow basalts form as the submarine lavas at mid- ocean ridges cool. The initial stages of continental plate divergence can result in more silica-rich volcanism, due to the silica-rich nature of the continental crust. Convergent Boundary: Convergent plate boundary volcanism can be complex. It typically produces andesitic lavas and this results in formation of stratovolcanoes. However, basaltic volcanism is also common at convergent boundaries. The Cascade Volcanic Chain is an example of the variety of volcanism present at a convergent boundary. The Cascade chain includes stratovolcanoes, shield volcanoes, pyroclastic deposits, and obsidian domes. Hot Spots: (Oceanic-basalt or Continental-rhyolite): This can be anywhere in the lithosphere. If they occur within oceanic crust (like Hawaii), they produce basalt

43 volcanism and shield volcanoes. If they occur within continental crust they can be silica rich and produce very explosive volcanoes such as the Yellowstone Caldera.

Geologic Hazards / Risk  Lava Flows – most only travel a few meters per hour and are slow enough for people to get out of the way.  Pyroclastic Hazards; o Ash falls o Lateral blast o Pyroclastic flows -ash flow (very fast and burns up everything in its path)  Poisonous Gas - H20, C02, S02 - suffocation  Lahars / Mudslides o Related to rapidly melted snow/ice o Flow rates: volcano base= up to 40 meters/second o 1Km out on plain = up to 10 meters/second o May be triggered by earthquakes, storms, gravity, volcanic eruptions o Travel Rapidly, may be little advance warning.

Prediction of Volcanic Eruptions  seismic activity - earthquakes  thermal, gravity, magnetic, electrical changes  tilting or swelling (ground level change)  gas emissions  historical information  rock type - silica rich or not?  Usually days to hours of notice. Size and direction of blast are harder to predict.

Preparation  Identify Potentially Hazardous Volcanoes o Plate Boundaries o Past History - Dating of Deposits o Current Status - Predictors  Identify Nature of Hazard o Rock Type - How Explosive o Other Hazards - Lahars, Poisonous Gas  Education, Zoning, Evacuation Plans  Continued Monitoring

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Magma Types and Volcanic Landforms Tendency for Volcano Type; Volcanic Composition Silica Content Viscosity Pyroclastic Landform (explosiveness)

Shield Volcano Mafic Basalt Plateau (Flood Basalt) 50% = low Low Least Basaltic Magma Cinder Cone Underwater Fissure

Intermediate Composite Volcano 60% = Andesitic Magma Intermediate Intermediate (Stratovolcano) intermediate Volcanic Domes

Felsic (Silicic) Volcanic Domes (Obsidian) 70% or greater Rhyolite Magma High Greatest Calderas (Supervolcanoes) = high

Types of Volcanoes Volcano Type Characteristics Examples Low Very fluid basaltic lava; Columbia River Plateau Viscosity Flood Basalt; Widespread flows emitted from Deccan Plateau (India) Basalt Plateau fissures

Shield Volcano Basalt lava forming a shallow- Hawaiian Volcanoes; sided cone Medicine Mountain Volcano

Underwater Basalt erupts in the deep ocean. Mid Atlantic Ridge Fissure The presence of water creates small East Pacific Rise explosions as the water is West Mata Volcano vaporized. New oceanic crust is formed.

Cinder Cone Explosive pyroclastic eruptions; Paricutin (Mexico);

small, steep-sided cone; sometimes Numerous cones in Lava Beds

associated with Shield Volcanoes. National Monument; Red Mountain (Arizona)

Composite More viscous lava (usually Mount Shasta

Volcano (or andesitic); steep-sided large cone; Mount Rainier

Stratovolcano) eruptions include lava flows as well Mount Saint Helens as more explosive pyroclastic eruptions, including small pyroclastic flows. Volcanic Domes Very viscous lava (may be volcanic Mount St. Helens Lava Domes; or Plugs glass); generally, small and Mono Craters associated with calderas or composite volcanoes. High Caldera from a Very large volcano explosion and Yellowstone collapse; very large pyroclastic Viscosity Caldera Long Valley Eruption flows. Mt. Mazama (Crater Lake)

Tables: Bazard and Wright, 2017

45 Worksheet 5.1: Volcanoes 1. Mt. Hood in Oregon is a composite volcano. If you were to hike up Mt.Hood, what type of rock would you expect to find most often when you stop to observe outcrops along your way?

2. Last summer, I visited an obsidian flow in the Newberry Caldera in Central Oregon. What is the composition of the magma that produced this flow?

3. The Big Island of Hawaii is composed of multiple Shield Volcanoes, describe the appearance (color, texture, phenocrysts) of rocks that you would find in Hawaii.

4. Describe the type of volcano that would be expected at each of the following settings. a. A hot spot located in the middle of an oceanic plate.

b. A convergent plate boundary with an oceanic plate subducting beneath a continental plate.

c. A hot spot within a continental plate.

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods 5. Label at least one dike and at least one sill in the cross section below.

6. Refer to the image below showing potential volcanic hazards. What type of volcano is pictured and how can you tell?

USGS Public Domain

47 Modified from USGS public domain map

7. Study the volcanic hazard map above. This map shows the hazards associated with an eruption of Mt. Rainier. Note that Seattle is located just off the map to the north of Tacoma. Which of these hazards do you think is most concerning to public officials in Washington State? Why?

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Lesson Six: Weathering and Sedimentary Rocks Background Reading: Sedimentary Processes The formation of sedimentary rocks is the result of several processes. The fundamental processes are weathering of pre-existing rocks, transport of sediment, deposition of sediment, and finally cementation and other processes that occur after deposition (this is called diagenesis). This progression is shown below.

Weathering Transport Deposition Cementation / Diagenesis Weathering The process begins with weathering. Weathering consists of both mechanical weathering (or sometimes called physical weathering) and chemical weathering. Mechanical weathering breaks rocks down into pieces that then provide more surface for chemicals to attack. Thus, mechanical weathering speeds up the weathering processes by providing more surfaces for the chemical to attack. Mechanical Weathering Examples of mechanical weathering are provided in Worksheet 6.1on page 54.

Chemical Weathering Oxidation – reaction with oxygen – rust (hematite, limonite) Solution – dissolving of minerals and release of ions; example: salt (halite) dissolving in water Hydrolysis– chemical reactions that produce clay minerals

Chemical weathering is aided by the presence of Carbonic acid in rainwater and groundwater. CO2 in atmosphere and soil dissolves in water to form carbonic acid: Carbonic acid will dissolve calcite (CaCO3) to release calcium into solution. It can also aid in weathering feldspars and other minerals. Many minerals weather to clay and release ions: For example, Potassium Feldspar reacts with Carbonic Acid to produce Kaolinite clay, potassium, and silica

Quartz is very stable and does not easily weather due to chemical (or mechanical) processes.

49 Transport: Mechanisms of sediment transport include Rivers, Wind, Glaciers, Gravity,Waves Weathering continues during transport. Other important processes also occur during transport. These processes include: Rounding – This is related to length and mechanism of transport Transport by rives, waves, and wind cause rounding. There is less rounding with short transport and with glacier transport. Angularity and sphericity are described in the textbook. These are similar in concept to the idea of evaluating grains by how they have been smoothed and eroded during transport. However, we will keep things simple and only consider rounding in our discussion of how grains mechanically change during transport.

Sorting- is the degree to which grains are similar in size Sorting is related to length of transport. Longer transport generally results in better sorting. In general, the size of grains deposited is related to the energy of transport. This is a key concept and something we will use in evaluating depositional environment (described below). Therefore, large grains are the only grains that will be deposited in rapidly moving water, and small grains are deposited in slow moving water after all of the larger moving grains have already been deposited (upstream in faster moving water). Small grains are deposited in areas such as bays, lakes, or the open ocean, where the transport energy is low. Wind and river transport is often an effective method of sorting. Glacial transport is often a poor means of sorting (the exception being the stream transport at the end of a glacier).

Deposition: deposition occurs when transport stops. Depositional Environments are described as: The geographic setting where sediment accumulates. We will consider three main types of depositional environments: 1. Terrestrial (Nonmarine). This is sometimes called continental, 2. Marine, 3. Transitional (shoreline) These types can then be subdivided by considering the energy of the setting: low, medium, high energy and specific conditions (rivers, dunes, glaciers)

Example of a depositional environment: A mountain steam is a medium to high energy terrestrial depositional environment. In general, rivers represent several depositional environments depending on the energy of each environment within the river. For example, we would expect larger grains to be deposited in the high-energy channel environment and small grains (silt or clay) to be deposited in the low-energy environment of the river banks or floodplain.

Post-depositional changes: Diagenesis Diagenesis is a collective term for all of the chemical, physical and biological changes that take place after deposition Lithification: an important diagenetic process that includes compaction and cementation to form a hardened sedimentary rock. The cementing agents produced include: quartz, calcite, hematite (iron oxides) Oxidation: oxidation of iron-bearing minerals in the rock give a common red/orange color.

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Sedimentary Rocks

Sedimentary rocks are formed in two general ways. Clastic sedimentary rocks are formed when sediments are deposited, compacted, and cemented. Chemical and biochemical sedimentary rocks are formed when minerals precipitate from water, or when minerals precipitated by an organism are cemented together.

Clastic sedimentary rocks are characterized by the size, shape, and (for coarse-grained rocks) the composition of the clasts. The clasts sizes are divided into the following categories: Gravel to Boulder size: >2mm Sand Size: 0.0625mm-2mm (you can see most sand sized grains) Silt Size: 0.004mm-0.0625mm (grains cannot easily be seen, but feels “gritty”) Clay Size: <0.004mm (feels smooth and powdery)

Clastic Sedimentary Rock Names Conglomerate is made mostly of rounded gravel- to boulder-sized clasts. (most of the grains are larger than sand size) Breccia is made mostly of angular gravel- to boulder-sized clasts. (most of the grains are larger than sand size)

Sandstones are made mostly of sand-sized clasts. These rocks are classified based on the composition of grains and the amount and type of material between the grains. They are also described in terms of rounding and sorting of grains. Quartz-Rich Sandstone (or Arenite) is made of almost all quartz grains with a quartz cement. Wacke Sandstone (or Graywacke) has a variety of grain types and mud between grains. This is a common sandstone in Humboldt County. You can think of this as a “dirty” sandstone. Arkose Sandstone contains abundant feldspar. These rocks are common near exposed granite. Note: (We will not be using Lithic Sandstone, which is described in the textbook).

Siltstone and Claystone are formed from cemented silt or clay clasts. Mudstone is composed of both clay and silt. Shale is either Siltstones or Mudstone with distinctive, thin layers or partings.

Chemical and Biochemical rocks are characterized by specific minerals. Common minerals in Chemical Sedimentary Rocks: Halite, Gypsum, Calcite, and Silica (quartz) can precipitate from water.

Crystalline Limestone is formed by precipitation of calcite from water. Fossiliferous Limestone is formed from the accumulation of calcite-rich organic fragments (shells). Muddy Limestone (Micrite) looks similar to mudstone, but the mudstone is calcite rich Chalk – powdery calcite-rich rock formed from the accumulation of microscopic calcite forming organisms – this one reacts to hydrochloric acid. Clastic Limestone is a clastic rock (formed of grains), but the grains are calcite rich Chert is formed either out of solution (from silica rich water), or from accumulation of organic fragments (very small silica-rich shells). Diatomite – powdery silica-rich rock formed from the accumulation of one-celled diatoms. Evaporites: Salt (halite) and Gypsum deposits are formed as water evaporates.

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Textural Features of Sedimentary Rocks Grain Sizes Grain Shapes Grain Arrangements

Gravel Size and Larger greater than 2 mm

Sand Sizes Ranges from Very-Coarse to Very-Fine Grained Sand 2mm to 1/16 mm Grains can be seen with the unaided eye.

Silt Sizes 1/16mm to 1/250mm (.0625 - .004mm)

Grains not visible, but feel “gritty”

Clay Sizes Less than 1/256mm, (<0.004mm)

Grains not visible, feels smooth. Grains cannot be seen with a common microscope Images: Bazard, 2012 and Public Domain

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

Sedimentary Rock Classification Chart

Clastic Sedimentary Rocks Chemical / Biochemical Sedimentary Rocks Grain Size Calcite-Rich Rocks Silica-Rich Rocks

Breccia (angular grains) Crystalline Limestone Chert (includes flint, jasper, >2mm chalcedony, agate) (granule to boulders) Conglomerate (rounded grains) Fossil-Rich Limestone Diatomite (powdery, silica- Mud-Rich Limestone (Micrite) rich, from diatoms) Sandstones: Chalk (powdery limestone) 2mm-1/16mm Quartz-Rich Sandstone (Arenite) (very-coarse to very-fine grained sand) Feldspar-Rich Sandstone (Arkose)

Mud-Rich Sandstone (Graywacke)

Less than 1/16mm (includes silt and clay) Mudstone (massive) Rocks Made of Evaporite Minerals  Grains not seen Halite – Rock Salt  Rocks range from Shale (finely layered silt and clay) Rock Gypsum gritty (silt content) to smooth (clay rich)

53 Worksheet 6.1: Sediment

Weathering is the breakdown of rocks at the surface of the earth. Mechanical (or physical) weathering results as force or pressure is applied to a rock resulting in fracture into smaller rock fragments that retain their chemical composition. Chemical weathering results from chemical reactions that break down the minerals within the rock at a molecular level. 1. Characterized each of the weathering processes in the list below as either mechanical or chemical by writing an M or a C next to the process a. A rust colored band appears along an existing crack in a rock. b. Exfoliation (pressure release fracturing) c. Frost wedging d. Tree root wedging e. Lichen growth (a moss-like organism that lives on the surface of rocks) f. Putting HCl on a calcite sample in lab g. The deterioration of the gargoyles on the Notre Dame h. Abrasion (sediment is rubbed against a rock) i. Gravel in soil breaks down into clay j. Salt wedging (in coastal areas salt crystals grow in cracks in rocks, expanding and breaking the rocks)

2. Consider the chemical weathering of granite. Use the table below to identify the minerals that will remain after complete weathering.

Products of Weathering Mineral Residual Products Material in Solution (minerals) (Ions) Quartz Grains Silica Quartz (Quartz does not chemically weather easily) Clay Minerals Silica, K, Na, Ca Feldspars (K, Na, Ca) Micas (Biotite, Muscovite) Clay Minerals Silica, K, Mg Iron-Oxide Minerals Clay Minerals, Silica, Ca, Mg Amphibole Iron-Oxide Minerals Clay Minerals, Silica, Mg Olivine and Pyroxne Iron-Oxide Minerals

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

3. For each of the following characteristics, identify whether the characteristic generally increases or decreases with transport time. (Write I or D next to the characteristic) a. Grain size b. Grain sorting c. Grain rounding d. Percent Feldspar e. Percent Quartz

4. Organize the list of depositional environments based on the energy of the depositional environment:

Sandy ocean beach Windblown desert Lake bottom Glacier Flooding mountain stream River floodplain

Energy Depositional Environment Maximum Grain Size High Energy

Low Energy

5. Complete the Maximum Grain Size column in the table above with grain size terms such as “boulder” or “fine sand”

55 6. Below is a list of descriptions of sedimentary rock units and a list of specific depositional environments. Match the correct depositional environment with the rock that most likely formed in that environment. (Note: There may be one trick question in this)

Rock 1: Poorly sorted, angular, arkosic conglomerate. Contains many granite rock fragments. Pink to dark red in color. Rock 2: Well sorted, well rounded, medium grained quartz sandstone. Tan to gray in color. Rock 3: Well sorted, well rounded, fine grained quartz sandstone. Pink to red in color. Rock 4: Fine grained limestone containing abundant marine fossils. Rock 5: Mudstone and shale with layers of evaporite minerals such as halite and gypsum.

Depositional Environments: Continental Shelf: The ocean, well past the tidal zone, but still within the continental crust. Desert Dunes: Very large dunes, some up to 100 meters high. Similar to the Sahara. Alluvial Fan: A fan shaped deposit of sediment at the base of a mountain range, where mountain streams flow into flat valleys. These are common in Death Valley. Ocean Beach: You know, a beach. Playa Lake: A shallow lake in a desert valley that sometimes dries completely.

Rock Depositional Environment 1 2 3 4 5

7. The sketch below shows a cross section view of cross bedding. Label the bedding and the cross bedding and add an arrow showing the direction of current flow.

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Lab 6.2: Analyzing Sediment Exercise #1: Analyze the sediment sample(s) provided and describe the rounding and sorting of the sample

Exercise #2: Make a grain size card. Use the Sieve to separate the sediment into different grain sizes. Glue a small portion of each grain size onto a single card and label the sizes (use terms such as larger than sand, coarse sand, fine sand, etc.)

Exercise #3: Decomposed Rock Sample Clastic sedimentary rocks may include fragments of pre-existing rocks. A. List the minerals you can identify in these rock fragments?

B. What was the pre-existing rock?

C. Are there any products of chemical weathering present? If so what are they?

Exercise #4 Sandstones For each of the sandstones describe: Graing Size Range: The smallest grain size and the largest grain size present (e.g. silt to granule) Median Grain Size: estimate that average grain size (what size are most of the grains) Grain Sorting and Grain Rounding Grain Composition: In particular is there quartz, feldspar or mud (silt and clay) present Cement: If possible identify the mineral that composes the cement Rock Name (e.g. Arkose)

Grain Median Grain Grain Grain Cement Rock Size grain size Sorting Rounding composition Name Range A

B

C

57 Lab 6.3: Sedimentary Knowns Use the labeled samples provided to answer these questions Look at the specimens and answer the questions below.

Rock Set 1: How can one distinguish Breccia from Conglomerate?

Rock Set 2: How can one distinguish Sandstone from Mudstone (or shale)?

Rock Set 3: How can one distinguish Fossiliferous Limestone from Crystalline Limestone?

Rock Set 4: How can one distinguish Micrite (muddy limestone) from Chert?

How can one distinguish Micrite from Mudstone?

How can one distinguish Mudstone from Shale?

Rock Set 5: How can one distinguish a Quartz-Rich Sandstone from Graywacke Sandstone?

How can one distinguish an Arkose Sandstone from a Quartz-rich Sandstone?

Rock Set 6: How does Diatomite differ from Chalk?

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

Lab 6.4: Sedimentary Unknowns: * These properties may not apply to all specimens and in some cases they may be left blank. Clastic or Grain Size Grain Rounding and Grain composition Cement (clastic) or Acid Fossils Name Chem/BioChem? (for Clastic)* Sorting (for Clastic)* Mineral (chem) Test (for Clastic)* Composition

A

B

C

D

E

F

G

59 Clastic or Grain Size Grain Rounding and Grain composition Cement (clastic) or Acid Fossils Name Chem/BioChem? (for Clastic)* Sorting (for Clastic)* Mineral (chem) Test (for Clastic)* Composition H

I

J

K

L

M

N

O

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Lesson Seven: Metamorphic Rocks

Background Reading: Metamorphic Rocks Metamorphic Rocks – These are rocks that have been changed from pre-existing rock due to heat and or pressure, without melting.

Parent Rock (or protolith): These are both names for the rock that existed prior to metamorphism. For example, limestone is a protolith that changes to marble due to metamorphism. The igneous rock peridotite is a protolith that changes to serpentinite (the California State rock!).

Grade: The grade of a metamorphic rock refers to the degree of change during metamorphism and ultimately to the conditions present during metamorphism. We will consider three general categories of grade: low, medium, and high grade. Low grade rocks have been subjected to low degrees of heat and/or pressure, whereas high grade rocks have been subjected to high degrees of heat and pressure.

Metamorphic Process include heat, pressure and fluid migration through the rock. All three of these can cause ions (atoms that are in the pre-existing rock) to migrate to new locations where they form new minerals. One of the changes we will see is the presence of new (often shiny or sparkling) minerals. Micas are often formed during metamorphism and these can give the rocks a shine or sparkle depending on the size of the mica crystals.

Something to keep in mind – minerals that were stable (were not changing) in the pre-existing rock become unstable under the new heat and pressure conditions. Therefore the atoms (ions) in the pre-existing minerals leave the mineral structure and migrate to new positions to form new minerals. This is how the rock changes. These changes can be very obvious when conditions allow for big, new, sparkly minerals to be formed, or they can be subtle when the mineral changes only produce minor changes in the texture or hardness of the rock.

Heat: this is the energy that drives ion migration and recrystallization. The new crystals are stable at higher temperatures. Example: clays will often recrystallize to form muscovite and biotite (micas). Pressure: this causes compaction and the differential stress (more pressure in one direction than another) can cause squeezing in a preferred direction. This occurs in tectonically active areas. In these cases the minerals grow perpendicular to stress direction and cause a texture known as foliation (see changes listed below). Fluids – hot fluids facilitate migration of ions. Water in pore space of sedimentary rocks provides often provide the fluids involved in this process. Metamorphic Changes: We will consider the following types of changes that occur during metamorphism: Texture changes and Mineralogical changes (changes in the mineral composition of the pre-existing rocks.

61 Changes in Texture Foliation – a preferred orientation of minerals is developed due to differential stress (see pressure discussion). Foliation includes Slaty Cleavage, Schistocity, Gneissic Banding. We will see example of these in the lab. In general you can think of foliation as a “grain” or “fabric” in the same way that wood or cloth has a preferred orientation that makes it easier to split or tear in a particular direction. Crystalline Texture (non foliated) – quartz and calcite are equal-dimensional crystals, so they do not align in a preferred direction to produce foliation. Instead the crystals just tend to get larger with higher grades of metamorphism. Porphyroblastic – Some minerals tend to grow more rapidly in the metamorphic environment than others. Consequently large crystals can be formed within a smaller crystalline rock. Garnets are good examples of crystals that form large crystals and give a metamorphic rock a porphyroblastic texture (this texture is similar to the porphyritic texstures of igneous rocks).

Mineral Changes in Metamorphic Rocks During metamorphism, new minerals form which are stable in the new metamorphic environment. Some minerals are good indicators of a specific grade of metamorphism. These are called index minerals. Index Minerals include chlorite (low grade), muscovite and biotite (med. grade), garnet (med. to high grade) Quartz, Calcite, Feldspars are stable in a variety of temperatures and pressures; consequently, they are not good index minerals. The new metamorphic minerals that are produced reflect the protolith (or parent rock) Chlorite – forms from the ferromagnessium minerals in basalt Micas – form from clays that are in sedimentary protoliths Talc– forms from mafic minerals that are in ultramafic rocks such as peridotite Serpentine –forms from the metamorphism of peridotite in the presence of water. Metamorphic Environments: A metamorphic environment is the geologic/tectonic settings where a metamorphic rock is formed. There are several ways of categorizing these environments. The categorization presented below is similar to the one presented in the textbook. However, I have lumped the environments under two big subdivisions: Localized, and Larger Areas.

Localized (although some of these can occur over large areas) Contact / Thermal: this environment exists when the intense heat of magma “bakes” the surrounding rock. Contact metamorphic rocks are typically not foliated. Batholiths can produce contact metamorphic zones that are several km wide. Hydrothermal: this occurs due to the hot fluids associated with geothermal activity. These rocks are typically not foliated and they may be associated with contact/thermal metamorphic environments. The presence of water can cause more intense ion migration and development of unique minerals. This environment is common at mid ocean ridges (divergent boundaries). It may result in concentrations of metals, such as those seen at “black smokers” under the ocean. Fault Zones: this environment is produced from the pressure (low heat) associated with faulting. Rocks formed in this environment develop a foliation that is usually parallel to the fault plane. This is sometimes called Dynamic Metamorphism

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

Larger Areas – these categories include environments that are not related to specific sources of heat or pressure, but rather to a larger geologic or tectonic setting. Burial Metamorphism – rocks formed in this environment are usually not foliated. This environment results from the confining pressure generated at 8 or more km deep; however, the stress is not differential so foliation is not produced. These are usually low grade metamorphic rocks with only subtle changes. Dynamothermal or Regional Metamorphism – This environment is associated with mountain building and the tectonic activity of a convergent plate boundary (subduction zone). This environment is capable of producing both differential stress and heat present. Consequently the rocks are usually foliated. The variation of heat and pressure within these environments can produce a variety of metamorphic grades. This results in metamorphic that range from slates to schists to gneiss. Most of our lab rocks are examples of rocks formed in a Dynamothermal environment.

Subduction zones are unique environments where high pressures but relatively low temperatures exist. When basaltic ocean crust (what is being subducted) is subjected to these conditions (high pressure, low heat) it results in something called blueschist metamorphism. The name comes from a bluish colored amphibole that develops when the mafic rock (basalt) changes in this high pressure/low temperature dynamothermal environment.

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Metamorphic Rocks

Metamorphic Terms: Protolith (or precursor or parent rock): the preexisting rock (prior to metamorphism). Grade: The degree of metamorphism; the amount of heat and pressure required to produce the rock. Foliation: parallel planar orientation of minerals.

Textures: Textures developed during metamorphism can be used to determine the grade (degree) of metamorphism and, in some cases, the protolith There are two main types of textures: foliated and nonfoliated. Foliated Textures: Slaty Cleavage: near perfect, planar foliation of very fine-grained minerals Phyllitic Texture: a “sheen” due to alignment of fine-grained (too small to see) platy minerals Schistosity: new metamorphic minerals are visible. They often create a “sparkly” appearance. Gneissic Texture: alternating layers of parallel to subparallel foliation of medium- to coarse- grained platy minerals. Nonfoliated Textures: crystalline: mass of crystals Some Low-grade metamorphism of basalt, conglomerate, sandstone, or other coarse- grained/crystalline rocks.

Minerals (these are in addition to minerals we have already studied in previous labs): Chlorite: green platy mineral (think of this as a green mica) Garnets: red-brown, spherical (polyhedral), glassy mineral Serpentine: mineral group that includes greenish white minerals (actinolite, lizardite)

Metamorphic Rocks: Foliated Metamorphic Rocks (distinguished by grade and foliation): Slate, Phyllite, Schist, Gneiss

Nonfoliated Rocks (distinguished by the minerals present): Quartzite, Marble, Greenstone (low grade basalt)

Foliated or nonfoliated: Serpentinite (low-med. grade) Metaconglomerate (low-med grade)

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

Typical transition in mineralogy during progressive metamorphism of shale

Increasing Metamorphism

Low Grade Intermediate Grade High Grade

Chlorite Muscovite (mica) Mineral Composition Biotite (mica) Garnet Quartz Calcite

Metamorphic Rock Type Shale - Slate - Phyllite Schist Gneiss (no alteration)

Metamorphic Rock Classification

Foliated Metamorphic Rocks Non-Foliated Metamorphic Rocks Sometimes foliated

Name Grade Protolith Name Grade Protolith Name Grade Protolith

Slate Low Shale Quartzite Variable Quartz-rich Sandstone, Chert Serpentinite Low Peridotite

Phyllite Low/Med Shale Marble Variable Limestone Metaconglomerate Low/Med Conglomerate

Schist Med –High Variable Greenstone Low grade Basalt

Gneiss High Variable

65 Worksheet 7.1: Metamorphic Rocks

1. The diagram above provides an example of how metamorphic foliation develops. To help clarify the difference between sedimentary bedding and metamorphic foliation, use this example to fill out the table below with the orientation of each structure in each step of the diagram above. The orientation can be horizontal, vertical, angled or not present (if the structure does not exist at that step).

Orientation of Step 1 Step 2 Step 3 structure: Sedimentary Bedding Metamorphic Foliation

2. Use the following vocabulary to fill in the blanks in the paragraph. Atoms Minerals Rocks

In most cases (except where rocks are highly altered by hydrothermal fluids), ______do not significantly change overall chemical composition during metamorphism, so the ______in the metamorphic rock will essentailly be the same as the ______in the protolith. However, the ______can combine in new ways under heat and pressure creating new ______that were not present in the protolith.

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3. Use the letter L, I, H to show which of the following minerals indicates a Low, Intermediate, or High grade metamorphic rock. Write “All” if the mineral does not provide evidence of a specific grade. Refer to the information on page 65. a. garnets ______b. chlorite ______c. quartz ______d. muscovite and biotite_____

The diagram below shows the theoretical pressure-temperature space of the crust. The lines with arrows represent possible paths that a metamorphic rock might take though the pressure and temperature space. The letters A-D represent points along those paths.

4. Match each of the letters A-D in the diagram above with the number in the cross section below that corresponds to the location where the pressure temperature conditions would occur.

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5. Label each of the lines with arrows on the pressure-temperature diagram on page 67 with one of the following descriptions: Mountain Belt Metamorphism Contact Metamorphism Subduction Metamorphism

6. Read each of the following rock descriptions. After each rock description write the letter corresponding to the zone in the pressure-temperature diagram where the rock would most likely form.

______Blueschist: This rock gets its name from the mineral Gluacaphane, a bluish colored amphibole that is stable at high pressure and low temperature.

______Gneiss: High grade, foliated metamorphic rock. Minerals separate into bands of minerals with similar chemistry.

______Hornfels: A non-foliated metamorphic rock that varies in mineral composition, but is often quite hard and may contain high-grade metamorphic minerals.

______Phyllite: A low grade metamorphic rock that often contains graphite, chlorite and muscovite. It has a shimmery appearance.

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Lab 7.2: Metamorphic Minerals and Known Metamorphic Rocks Minerals: Use the samples provided to answer these questions

Describe how to distinguish chlorite from mica (muscovite and biotite)

Describe three properties that help one distinguish quartz from calcite.

Describe the rock sample made of the serpentine group of minerals

Describe amphibole

Describe garnet

Known Metamorphic Rocks, use the labeled specimens to determine:

Rock Set 1: How can you distinguish Quartzite from Marble?

Rock Set 2: How can you distinguish Slate from Phyllite?

How can you distinguish Phyllite from Schist?

How can you distinguish Schist from Gneiss?

Rock Set 3: How can you distinguish Chlorite Schist from Serpentinite?

How can you distinguish Greenstone from Serpentinite?

Rock Set 4: How can you distinguish Gneiss from Quartzite?

Rock Set 5: How could you tell a metaconglomerate from a conglomerate (sedimentary rock)?

69 Lab 7.3: Unknown Metamorphic Rocks: Provide the metamorphic textures, minerals, grade, protolith and the rock name for each of these specimens. Only list the minerals you observed. * Grade and Protolith may be indeterminate for some rock types. Write NA in these sections if grade or protolith cannot be determined.

Specimen Foliated or Non- Minerals Acid Test Metamorphic Grade* Protolith* foliated? (if visible) (if it applies) Rock Name (if it applies) (if it applies)

A

B

C

D

E

F

G

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

Specimen Foliated or Non- Minerals Acid Test Metamorphic Grade* Protolith* foliated? (if visible) (if it applies) Rock Name (if it applies) (if it applies) (For foliated, list the type of foliation)

H

I

J

K

L

M

N

71 Sedimentary and Metamorphic Rock Lab Quiz - Study Guide You may use a sheet of notes (two sides of 8.5x11 inch paper). Computer generated text is OK, but no photocopies are allowed. You will not be able to use your labs. You may, however, transfer lab information to your sheet of notes.

Sedimentary Rocks – Be able to identify and describe the properties of: Clastic Sedimentary Rocks: Conglomerate, Breccia, Quartz-Rich Sandstone (Arenite), Feldspar-Rich Sandstone (Arkose), Mud-Rich Sandstone (Graywacke), Mudstone (Shale),

Chemical/Biochemical Sedimentary Rocks Fossiliferous Limestone, Crystalline Limestone, Micrite Chert Diatomite Chalk

Sample Sedimenatary Rock Questions List the sedimentary rock name

What is a distinguishing characteristic in this rock?

List the name of the mineral that makes up most of this rock

List a distinguishing characteristic of this rock

What mineral is common in this rock

Explain your criteria for assigning this rock name.

Photos of Sedimentary and Metamorphic Rock Specimens can be found on the course Canvas web site. They are also at the following URLs:

Sedimentary Rock Photos: http://tinyurl.com/g1sedrocks

Metamorphic Rock Photos: http://tinyurl.com/g1metrocks

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Metamorphic Rocks– Study Guide

Terminology: Protolith, Grade, and Foliation. Be able to list these (if appropriate ) for a given sample.

Minerals Be able to identify distinguishing minerals: quartz, calcite, muscovite, biotite, chloritie, amphibole, garnet

Know the characteristics and rock names of the following rock types:

Foliated Metamorphic Rocks: Slate Phyllite Schist Gneiss

Non-foliated Metamorphic Rocks Marble Quartzite Greenstone

Foliated and non-foliated varities Serpentinite. Metaconglomerate

Sample Questions for Metamorphic Rocks:

List the protolith for this rock.

List the name of this metamorphic rock

List the metamorphic grade

List one of the metamorphic minerals present in this rock (other than quartz)

List the metamorphic texture of this sample

Identify the rock sample using the specific rock name (this may be a igneous, sedimentary, or metamorphic rock).

There will be one or two samples that can be any rock type (igneous, sedimentary, metamorphic)

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Lesson Eight: Structural Geology Background Reading: Structural Geology Deformation of Rocks (Structural Geology)– Rocks are deformed in a variety of ways, but ultimately the deforming (bending or breaking) is the result of the rock being under stress.

Stress is defined as a force applied over a given area. Push your hand down on a table. You are applying a force to the area beneath your hand and as a result, stress has developed. The motion of plates and the overlying weight of rocks cause rocks to be stressed. There are three principle types of stress: Compression: material is squeezed (pushed together) Tension: material is pulled apart (stretched) Shear: material is torn (moves side-by-side) For our discussion, the material in all of these situations is rock.

Strain is the change in shape that results from stress.

Stress causes deformation (bending and breaking) that results in strain (a change in shape). In other words, stress causes strain.

There are two principle types of deformation – brittle deformation and ductile formation. Brittle deformation occurs when a material breaks. A rock breaking during faulting is an example of brittle deformation. Ductile deformation occurs when a material bends (and does not snap back). A rock bending during folding is an example of ductile deformation.

In this lesson we will be discussing two main categories of deformation – the folding of rocks and the faulting of rocks. Either of the two can occur when rocks are under the stresses that result from plate motions.

What determines if a rock folds or faults? The main factors are: Temperature, Pressure, Time (deformation rate), and Composition (what the rock is made of). In general, rock that is at higher temperatures and pressures, and stressed over a longer time period will experience folding (ductile deformation) and rock that is at lower temperatures and pressures and stressed more quickly will break. For this reason, geologists find that rocks behave in a ductile manner (and fold or flow) when they are buried at depths greater than 10km to 15km. Rocks closer to the surface are more likely to fracture or fault (behave in a brittle manner). However, rocks may experience both folding and faulting within the same rock and at a similar depth. Sometimes as rocks fold, they are brittle enough to eventually break and produce a fault. Humboldt Hill (behind CR) is an example of a hill produced by both folding and faulting (the Little Salmon Fault that dips under the campus).

75 Folding Folded Rock can be described in terms of either arched up folds (called anticlines, see the figure below) and arched down folds (called synclines). Each fold consists of two limbs of the arch and a hinge line at the top (or bottom of the trough) that is called the axis of the fold.

 Anticline has the oldest strata in the center (near axis) and dips away from the center (axis)

 Syncline has the youngest strata in the center and dips inward toward the center (the axis) ]

 An example of an anticline and syncline occurring together is shown below: Drawing by Bazard, 2012

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Orientation of strata that has been tilted as part of a fold. When only one limb of a fold is exposed, it appears as a tilted block of strata. The orientation of titled strata is described by two properties called Strike and Dip. Strike and Dip provide the orientation of the strata with respect to north, east, west, and south.

Strike and Dip: •Dip: Angle between horizontal and the bedding surface (plane surface). •Down-Dip Direction: direction of the bed dip. •Strike: Line perpendicular (90°) to down-dip direction. Line formed by intersection of horizontal plane and strata plane

Two examples showing the Strike and Dip of strata (part of a fold limb):

Map symbol showing Strike and Dip: Strike Line is parallel to the contact between types of strata. The Dip Direction is always 90 to the Strike Direction

Strike and Dip Map Symbol:

The geologic map shows strikeand dip symbols. The dip angle is shown in the cross-section.

77 Faulting (brittle deformation): A fault occurs where stress causes a rock to break and produces motion between opposite sides of a fracture. Faults are surfaces (like a sheet of paper or plywood) that are called fault planes. The orientation of the fault plane can also be described in terms of strike and dip.

I Dip-Slip Faults - These types of faults result in motion of rock up and down the dip of a fault plane.

USGS public domain figure Normal Fault: This is caused by horizontal Tension . Normal faults result in lengthening as the overhanging block (hanging wall) of a fault moves downward.

USGS public domain figure Reverse Fault (or “thrust” fault): This is caused by horizontal Compression, Reverse faults result in shortening as the overhanging block (hanging wall) of a fault moves upward. Thrust fault shallowly dipping (<45 degree) reverse fault.

USGS public domain figure Strike-Slip Faults: Faults motion is parallel to the strike of a fault Right-Lateral: Objects across fault move right Left-Lateral: Objects across fault move lef

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Worksheet 8.1: Moonstone Beach Field Trip Preparation All Figures by Emily Wright 2017 One of the goals of the Moonstone Beach field trip is to practice using a compass and working with maps. To prepare for this, we will do some practice on campus first. The compasses that we will use are Brunton Pocket Transit compasses. The class set includes two different forms of notation. Azimuth (360°) and Quandrant notation.

1. Fill in the numbers that belong in the empty boxes in the diagram above, by observing the pattern shown in other quadrants.

2. Write out the bearing of each of the gray lines in the illustration below. Use the example provided to guide you in how to write out quadrant notation.

79 3. On the map provided below, use a protractor (provided in class) to draw the following bearings: a. A bearing of 340° from point A b. A bearing of N80E from point B

4. On the diagram at right, observe the layout of the azimuth notation and the cardinal directions. What is unusual about the layout of the directions?

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods 5. Use the compass illustrations below to answer the following questions?

a. In what direction is the sighting arm pointing on Compass 1? (Use azimuth notation for your answer)

b. In what direction is the sighting arm pointing on Compass 2? (Use quadrant notation for your answer)

6. Brunton Pocket Transits are commonly used by geologists in part because they also include an inclinometer. In the sketch below, what is the dip (angle from horizontal) of the rock?

81 We will now construct a practice map of some flags put out in the lawn. You will need a compass (depending on class size, you may need to work in pairs) to take bearings and you will use your pace to measure distance.

Your pace is the length of two steps. Choose your favorite foot (left or right) and count the number of times that foot lands.

Landmark Type Bearing Beaing to Paces to Meters to Millimeters back to next next next to next (for last map)

7. Fill out the first five columns of the data table above with the data you gather in the “field”.

8. How many paces did it take you to walk 30m? (This number will be unique to you)

9. Use this information to find your personal pace length in meters.

10. Fill in the column “Meters to next” using your pace length as a conversion rate.

11. As a class, we will decide on an appropriate map scale. Write down the scale here:

12. Use the map scale to fill out the last column of the data table above.

We will construct our map as a class. You don’t need to draw anything at this point, but pay attention to the methods, as you will need to perform these on your own with data from Moonstone Beach. 82

Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

Worksheet 8.2: Geologic Structures 1. Write out the strike and dip measurement that is shown by the symbol below. Use a protractor to determine the strike. Write the strike in Quadrant format. You may want to refer to pg. 77

Strike:______Dip:______Dip Direction:______2. Convert the strike from the previous question into azimuth.

3. Draw the symbol for the following strike and dip measurement: 015°, 45° SE

4. Consider the following blocks (a, b, c) and answer the following for each a. describe the stress for each (tension, compression, shear) b. use half arrows to show the sense of motion on the fault c. for “a” and “b”, how will the dimension “l” change (shorter or longer) d. label each type of fault

83 5. For each of the fault cross sections below, label the Hanging Wall (HW), the Footwall (FW), draw the appropriate half-arrows on the fault and provide the fault name (there may be repeats).

6. Write a general rule for the age of geologic units in synclines and anticlines: Syncline:

Anticline:

7. Write a general rule for the dip of the limbs of a syncline and anticline: Syncline:

Anticline:

8. On the map at right draw in the following. It may help to consult pg. 76 and 77. a. The axis of the fold with the appropriate symbol for the type of fold and the plunge direction (if applicable) b. Strike and dip symbols on either side of the fold axis with dip measurements included (use a protractor and the cross section)

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Lab 8.3: Geologic Maps Figures in this lab were modified from the public domain USGS Geologic Map Series Part A: Masonville Quadrangle This activity is designed to accompany the Geologic Map of the Masonville Quadrangle, available in full size and color in class.

1. To get a sense of the overall patterns in the geology, on the small version of the map on pg. 89, color in the following three units. Text and symbols on the small map are too small to read, so look for large scale trends. Also write the symbol for each unit (example: Ksf), the rock type(s) and the age (example: Cretaceous) Dakota Group (Use one green for all the different formations in the Dakota Group) Symbol: Rock Type: Age: Lyons Formation (light blue) Symbol: Rock Type: Age: Fountain Formation (purple) Symbol: Rock Type: Age:

2. There is a lot of yellow on the map that doesn’t follow the same pattern as the other colors, what is this and why does it not follow the pattern?

3. Locate the Devil’s backbone. (It is just north of the Big Thompson River in the eastern part of the map). A rock attitude measurement (strike and dip) has been taken at a road cut in the Morrison Formation (Jm) on Highway 34. Locate the appropriate symbol on the map. Use a protractor to measure the strike, then write out the measurement in the form: strike, dip, dip direction

85 4. In the following two questions, you will use the map and the B to B’ cross section to determine the attitude (strike and dip) of the Niobrara Formation on the east side of the map. This will be an estimate rather than a precise measurement. The attitudes plotted on the map are actually precise measurements made with a compass in the field. a. Observe all the strike and dip symbols along the Devil’s Backbone. Notice that the strike lines are generally parallel to the green color stripe on the map. Use this same concept to estimate the strike of the Niobrara Formation (Kns) on the eastern edge of the map, right near the B’ end of the cross section line. Write your answer in the appropriate space below the next question. (Refer to Worksheet 8.1 Question 8 on page 84) b. Using the B to B’ cross section, measure the dip of the Niobrara formation (Kns) unit near the B’ end of the cross section. You will need a protractor. Strike (part a):______Dip(part b): ______Dip direction(part b): ______

5. Using the information from the previous question, draw the appropriate symbol for the strike and dip on the copied map section below. Try to make your symbol roughly the same size as the symbols already on the map.

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

6. Locate the Big Thompson Anticline on the map. Is the Big Thompson Anticline plunging or nonplunging? If it is plunging, in which direction does it plunge (as in North, South, East or West)?

7. Draw a sketch below of the symbol used along the line that marks the axis for the Big Thompson Anticline. Label the part of the symbol that indicates an anticline as well as the part that indicates direction of plunge.

8. If there were no symbol on the map, what information would you use to determine the direction of plunge?

9. True or false: the geologic unit in center of the Big Thompson Anticline is the oldest unit. 10. True or false: the limbs of the Big Thompson Anticline dip toward the axis. 11. Locate a syncline on the map. Circle the syncline on your small map. 12. On the small map, I have added a C to C’ line. Complete the cross section that has been started for you below. Color in the units using approximately the same colors as the map. Add dotted lines to project the units above ground (where they would have been before they were eroded).

87 13. Locate the Green Ridge Fault on the map and in the B to B’ cross section. Use a red colored pencil to trace over the line on your small map. 14. Below is a blow up of the Green Ridge Fault in cross section. Use the Fountain Formation (PPf) to determine which way the fault has been offset. Add half arrows to the blow up below. What type of fault it this (Normal, Reverse or Strike-Slip)?

Part B: Geologic Map of the Eel River Basin Use the Geologic Map of the Eel River Basin (provided in class) to answer the following questions: 15. Locate the CR campus. What are the brown Quaternary deposits in the hills above campus?

16. What geologic structures are present in the map area? How have these structures shaped the topography (hills and valleys ect.)?

17. Find the natural gas wells on Tompkins Hill. Are these wells located on a syncline or an anticline?

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Lesson Nine: Geologic Time Background Reading: Geologic Time Relative age dates are determined by placing rocks and events in their proper sequence of formation

General Principles of relative age dating:

1. Superposition In an undeformed sequence of sedimentary rocks (or layered igneous rocks), the oldest rocks are on the bottom.

2. Principle of original horizontality Layers of sediment are generally deposited in a horizontal position. Rock layers that are flat have not been disturbed.

3. Principle of cross-cutting relationships Younger features cut across older features. So faults cutting through rocks are younger than what they cut through. Igneous intrusions that cut through rocks are younger than the rocks they cut through. Also, an erosional surface that cuts across a body of rock is younger than the underlying body of rock.

5. Fossil Succession

6. Unconformity An unconformity is a break in the rock record produced by erosion and/or nondeposition of rock units.

7. Inclusions An inclusion is a piece of rock that is enclosed within another rock. Rock containing the inclusion is younger than the inclusion.

Numeric Time: Numerical dates –the actual number of years that have passed since an event occurred (also known as absolute age dating). Numeric time methods use a process that happens at a known rate.

Modern numeric dating in the geologic sciences is based on many types of known rates such as tree ring dating where we know the rate of growth of rings (summer and winter rings) or lichen growth on boulders (to determine how long the boulder of a landslide has been sitting in one place). However, most numerical ages come from analysis of radioactive decay of elements that are within minerals or other compounds. This is called “Radiometric Dating” or “Isotopic Dating”

Radiometric dating (or Isotopic dating) is based on the transformation of one element into either another element or an Isotope of that element. An Isotope is an element with the same number of protons (same element) in its nucleus as other isotopes of the same element, but it has a different numbers of neutrons. For example: Carbon-12 and Carbon 14 are both isotopes of the element carbon. Both have six protons in their nucleus (this is what defines them as being carbon). However,

91 Carbon 12 has six neutrons and Carbon 14 has eight neutrons. Therefore Carbon 14 is actually heavier than Carbon 12.

Transformation Process of Radioactive Decay Parent material decays to a daughter product Rate of Decay is the “clock” that allows determination of time. This is what happens at a known rate to allow a numeric age to be calculated Half-Life: the amount of time it takes for half of atoms in unstable parent material to decay to a stable daughter product. Each atom has 50% chance of decaying to the new material in 1 half-life Radioactive decay is an exponential decay: new decay is a percentage of remaining material.

Assumptions of Radioactive Decay Analysis • Minerals are closed systems, or loss and gain can be accounted for. • Initial Parent and Daughter are known. • Decay rate is constant for each element (isotope) and cannot be affected by pressure or temperature.  This is a statistical method based on probability (50% chance of decay in one half life). Statistics are only valid for large data sets. The atoms in a mineral represent a very large data set.

Importance of radiometric dating  Radiometric dating is a complex procedure that requires precise measurement  Rocks from several localities have been dated at more than 3 billion years  This confirms the idea that geologic time is immense

Limitations:  Not all rocks can be dated using radiometric dates – requires unstable material.  It is important to know what is being dated. If the isotopes are from igneous or metamorphic crystals, then the ages are the age of crystallization (from magma or metamorphism). In the case of Carbon-14 isotopes, the dating provides the age when the organic material stopped taking in carbon (the death of the organism)  The half life of an isotopes limits the age range that can be provided by the isotopes. Carbon-14 isotopes decay relatively rapidly so it can only date materials within the last 50,000-70,000 years. Uranium isotopes have very long half lifes and can be used to age date material several billion years old.  All age dates include estimates of error. The error estimates are based on the precision of lab equipment and our knowledge of parameters such as how well we know the half lifes or the initial content of an isotope in the environment. It is important to understand the error estimate before applying the age to a geologic study.

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Mathematical Reasoning Behind Radioactive Decay Analysis. The following is provided for those who have an interest in the mathematics used to derive radiometric ages. It will not be on the test

How do scientists determine the Half Life if it is thousands (or millions to billions of years) long?

Good question – here is a general description of the mathematics and reasoning used to determine the half life for a particular element (or isotope):

Radioactive Decay is an exponential process. Therefore “it can be shown” that the following is true: Natural logarithm (or ln) of Nt/No = kt This is equation #1: ln (Nt/No) = kt Where: No = amount of parent at a beginning time Nt = amount of parent after time t k = unique decay rate for the material, and is called the decay constant

After one half-life has elapsed: Nt/No = 1/2 So when t=one half life, equation #1 is: ln (1/2)= kt Therefore The half-life= ln (1/2) / k This is equation #2 k (the decay constant) can be determined by analyzing the relationship shown in equation #1 for a short amount of time. If t is known and Nt and No can be measured (over a short time) then one can solve for k, Once k is known then one can solve equation #2 for the value of the half-life. This is how half- lifes are determined – by using shorter amounts of time to determine k, and then using equation #2 to solve for the half life.

93 Worksheet 9.1: Relative Time

Refer to the geologic profile shown below. Note that W, L, M, O, A, P, and J represent the time of deposition of sedimentary strata. B and K represent the age of igneous intrusions. C represents the age of the fault motion.

1. List the letters shown to provide a plausible sequence of geologic events (from oldest to youngest) to account for this profile.

2. The specific name for the contact represented by the letter U is: ______. Describe the sequence of events that formed U:

3. Has intrusion B been tilted? What is your evidence?

4. Has intrusion K been tilted? What is your evidence? What additional evidence would be helpful to better answer this question?

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Worksheet 9.2 -Absolute Time Radioactive decay. Radiometric dating uses radioactive elements that decay by emitting nuclear particles. These radioactive elements are called the parent material. In the decay process they are transformed into new elements called the daughter material. The rate of decay (how fast it occurs) is described in terms of a half-life. A half-life is the amount of time required for half of the parent atoms to decay to the daughter atoms. For example, one type of Uranium (235) has a half-life of 713 million years. The daughter product is Lead (207). This means that after 713 million years one gram of this Uranium parent would change leaving ½ gram of Uranium and ½ gram of Lead.

1. Consider the decay of Carbon-14. It has a half-life of 5730 years. a. Complete the graph below to show how 100% of the Carbon changes over several half-lifes. b. How much parent (in %) is left after 4 half-lifes? c. How old is this material (after 4 half-lifes) d. Material older than about 50,000 years cannot be dated using Carbon-14. What is the reason for this?

95 The Figure below shows an area where two igneous intrusions (dikes) cut across several sedimentary layers. The intrusions (Igneous Dike A and B) are composed of igneous rock that contains a small amount of unstable parent material. This is radioactive Element (isotope) X. The other figure below shows a decay curve for Element X.

2. Use the decay curve to determine the half-life of Element X

3. Use the percentage of X to date: a. The age of metamorphism of the schist b. The age of the intrusion of A (age of crystallization) c. The age of the intrusion of B (age of crystallization)

4. What is the possible age range of layers 1-4? 5. What is the possible age range of layers 5-11? 6. What is the maximum age of layer 12? Figures: Bazard, 2012

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Name:______Date:______GEOL1 Physical Geology Laboratory Manual College of the Redwoods Worksheet 9.3: Geologic Time Scale Geologic time has been subdivided into different units of time. This was done in the 19th century based on relative time principles and the fossil record. Numeric ages were added in the 20th century. The subdivisions are based on major changes in life form (fossils) and/or climate (as it influences life forms and rock types)

1. Write the following terms in order of size of the geologic time unit (largest to smallest): Period, Eon, Epoch, Era.

2. Provide the numeric time for each of the following:

Holocene Epoch:

Cenozoic Era:

Phanerozoic Eon:

Quaternary Period:

NPS Public Domain NPS Public 97

Lab 9.4: Geologic Map of California 1. Find a location where some of the oldest rock in California is found. There are several locations with the oldest rock types. a. List a geographic location near at least one of them.

b. What is the age and rock type?

2. Describe the geology of the Sutter Butte region. What is the age of the rock and how do you think it was formed?

3. Look for linear trends and see if you can locate the San Andreas Fault on this map. Cite evidence from the map that indicates that there has been relative motion across this fault. Use the sense of motion to describe the type of fault that is present.

4. What is the age and rock type common in the Modoc Plateau region (northeastern California)

5. Find Yosemite Valley. What is the type and age of the rock surrounding this valley? What is the significance of the Qg unit?

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Lesson Ten: Landscape Evolution Background Reading: Topographic Maps

Latitude: Angle from the Equator, with the equator being zero and the poles being 90 degrees (either North or South). (National atlast.Gov - Public Domain)

Longitude: Position around the globe. Looking down at the pole and considering the Earth as a 360 degree circle. (National atlast.Gov - Public Domain)

Rules for contour lines 1. Every point on a contour line is at the same elevation. 2. Contour lines always separate points of higher and lower elevation. You must determine the up and down direction by examining adjacent features (valley, hill) 3. Contour lines always close to form a loop. 4. The Contour Interval is the elevation distance between contour lines. Every fifth line is heavier and is known as an index contour 5. Contour lines never cross one another, except in the very rare instance of an overhanging cliff (in that case the hidden contour is dashed) 6. Evenly spaced contour lines indicate a uniform slope. 7. Closely spaced contour lines indicate a steep slope. Widely spaced contour lines indicate a shallow slope. 8. A series of closed contours (irregular circle) indicates a hill. Depressions look similar but have hachure marks on the inward side of the contour line. 9. Contour lines form a V pattern when crossing streams. The narrow part of the V points upstream.

Background Reading: Landforms Landforms are a result of Uplift/Subsidence combined with Erosion/Deposition. Relative balance of uplift/subsidence and erosion/deposition determines the landscape. Uplift and Subsidence occur from folding, faulting, earth’s heat, and accumulation at volcanic centers. Erosion is caused by gravity that results in the movement of rock, water, and ice. Erosion also results from wind (solar energy) and chemical reactions. Deposition results when these process slow and sediment stops being transported. When erosion and deposition are dominant, the landscapes become flatter and valleys broader. When uplift and subsidence are dominant, landscapes have more relief and valleys are deeper. Relief is the elevation difference between two points. Base Level – the level to which a stream erodes. Local base levels are the elevation of a lake or valley. The “ultimate” base level is sea level. However, some base levels are below sea level (can you guess where this would occur?).

Geomorphology Concepts of William Morris Davis – this is a historic starting point. Most modern geomorphologists don’t agree with the simplicity of Davis’ cycle and his concept that there is an “evolution “ of landscapes. However, his stages are still useful in understanding the influences on landscapes. Youthful Stage - active downcutting brought on by a base level change. This is caused by tectonic uplift and/or sea level drop. This produces rugged, high-relief landform Mature Stage – erosion and deposition begin to dominate and return the landscape to a lower-relief form. Peaks become rounded and river profiles become more gradual. Old Age – erosion and deposition dominate. Stream profiles become very gradual and the land elevation begins to approach the elevation of base level.

More modern ideas incorporate ideas of thresholds being reached, feedback, climatic changes and tectonic changes. These models can be quite complex.

Mass Movement refers to the downslope movement of rock, regolith, and soil under the direct influence of gravity. •Geologic process that often follows weathering •Combined effects: mass wasting and running water produce slopes and stream valleys •Mass Movement results in landform development

Colluvium (a definition): loose unconsolidated deposit at the foot of slopes (landslide deposits)

•Driving Forces: related to weight of materials (gravity acting on mass is weight). This includes weight of rock, weight of vegetation, weight of water, weight of human endeavors (houses, roads, underground tanks, pools, etc.)

Resisting Forces: related to the shear strength of materials. This includes the strength of rocks, roots, the down-slope portion of a slope, and manmade structures such as walls, tie-backs, etc. The following contribute to the resisting force: - Gravity pushing down on surface is a resisting force

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- Strength of earth material (Shear Strength) - Cementationand friction between grains - Orientation of bedding (stratification) and orientation of foliation or rock fabric - Vegetation (increasing shear strength) - Buttressing of Slope (Toe of Slope)

Important Factors for Mass Wasting •Steepness of Slope: Greater component of gravity –Percent Grade= (Rise/Run)*100 = (elev change/ horizontal)*100 •Water: –Small amounts of water increases cohesion and adds strength –Usually water adds weight (driving force) and reduces shear strength •Vegetation –Adds to shear strength (roots) –Removes water (transpiration) –Provides Protection from direct impact of rain –Adds weight, which may be a driving force •Rock Type –Wet clays and poorly cemented rock= low shear strength –Strike and Dip: orientation of bedding –Foliation: orientation of planar elements

What determines these factors?•Steepness of Slope: –Tectonic Forces (uplift); Earth Materials –Slope Modification: nature (rivers), people •Water: –Climate –Drainage –Vegetation •Rock Type –Nature –Modification by Humans

Classification: Flows • Debris Flow / Mudflow (including a lahar) • Earth Flow (on slopes, rather than drainages) • Creep Slides  Rotational (slump)  Translational (rock slide) Falls  Rock Fall and debris falls Subsidence  Slow – Basin collapse  Rapid – Sink holes

River Systems I Terminology: Discharge: the volume of water passing a point per time Load: volume of sediment being transported by a river Drainage Basin (watershed)/Drainage Divide: Entire area drained by a river system; separated from other drainage basins by a drainage divide Headwaters/Mouth (delta): beginning and end of a stream; steep to flat gradient. Rivers flow from the headwaters to the mouth (location of a delta). This system includes tributaries that flow into the trunk stream that eventually flows to a mouth. Tributaries: smaller streams that feed into a central channel (or trunk). Channel, Bed, and Banks: area where water flows (other than at times of a flood). Floodplain: flat, low-lying area flanking a stream that is subjected to flooding. Gradient: relief compared to horizontal distance. Profile: change in gradient along the course of a river. A river profile is typically steep near the headwaters and flatter near the mouth. Changes in uplift, rate of erosion, discharge, and base level effect the stream profile.

II Concepts and Processes: Base level: a level below which a stream cannot erode its valley; ultimate base level is sea level. Changes in relative base level influence the ability of a stream to erode and transport sediment. Thus, base level changes influence stream profiles. These changes involve relative down drop of base level, which can occur by uplift or base level drop (sea/lake level drop).

Erosion and Deposition Downcutting: vertical erosion. This process is enhanced by relative base level drop. Headward erosion: Rivers erode upstream toward the headwaters. This erosion results in the profile being adjusted to the base level. Meandering: side-to-side erosion. This process happens in a predictable way: deposition on inside bends (or meanders) to form point bars; erosion on outside bends (or meanders) to form cutbanks. When the gradient decreases, streams tend to meander. Braided Streams: Excess sediment causes a stream to deposit sediment and then to erode multiple channels through the deposit. This also occurs when a sudden decrease in gradient occurs. A similar process occurs at the delta. Delta Formation: As the gradient decreases near base level, a stream will deposit material. As the river erodes its way through this deposited sediment, it forms a delta (triangle-shaped landform). Floodplain Formation: during flooding, sediment is transported out of the channel into the slow moving water of the surrounding region. This sediment is deposited and forms the floodplain. River Terrace Formation: Drops in base level causes formation of a new floodplain at a lower elevation. The former floodplain is a river terrace. Drainage patterns reflect relief and regional steepness (topography), rock resistance (to weathering), climate, hydrology (drainage, size of the drainage basin, permeability of rock), structural controls on the rock (orientation of faults, folds, and uplifts)

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Worksheet 10.1 - Mass Movement

Photo by permission of JimFalls - CGS

1. Evaluate the situation above (at Big Lagoon, CA) in terms of driving forces and resisting forces. A beach adjacent to the Pacific ocean is at the base of the cliff. The bluff is composed of young sandstone and mudstone layers. This picture was taken shortly after a period of storms and high waves.

Resisting Forces (including how these forces were reduced):

Driving Forces (including what may have caused the slide):

2. Label each type of mass wasting using the classification described in the textbook and on page 101. a. The type of mass movement that takes place the most gradually b. Mass movement involving a slurry of large clasts, and rapid movement. c. The type of mass movement where a whole segment of rock moves down a curved surface d. Free fall of material from a steep slope (dry material)

Worksheet 10.2 - Rivers

1. Use the Letter “C” or the letters “PB” to show where at least two cutbanks and point bars are located in the figure below.

Drawing: Bazard, 2013

2. The area between the arrows represents the:______

3. Assume this river empties into a lake approximately one mile downstream. Describe how the channel will change if the lake level drops by several hundred feet.

River

4. The arrows in the diagram above are pointing toward: ______

5. These represent former: ______

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Worksheet 10.3 Landscapes 1. Provide a definition and example of the following: Relief:

Agent of Erosion:

2. Provide the requested information for each of the following situations

A. A steep mountain range with a deep valley to the east. The valley is filled with a thick accumulation of sediment. The mountain range is snow covered and prone to landslides. The valley includes streams and a lake.

Is this situation dominated more by uplift/subsidence or erosion/deposition?

List the agents and processes of erosion at work in this situation

List the depositional processes at work in this situtation

B. A broad floodplain with little relief. A large river meanders across this floodplain until it enters the ocean where a large delta has formed.

Is this situation dominated more by uplift/subsidence or erosion/deposition?

List the agents and processes of erosion at work in this situation

List the depositional processes at work in this situtation

Lab 10.4: Topographic Maps. Goals: To become familiar with reading and interpreting topographic maps and using a compass. Concepts and Terms: Latitude, Longitude, Magnetic Declination, Public Land Survey System, Principal Meridian, Base Line, Township, Range, Section, Scales, Contour Lines, Contour Interval, Topographic Profile, Vertical Exaggeration.

1. Refer to the Quadrangle Map Provided a. When was this map made? b. What is the map scale? c. What is the magnetic declination? d. Provide the approximate latitude and longitude of the feature described by your instructor

e. Draw a sketch showing how contour lines define a stream valley or creek bed.

2. Slopes (or grades) are often described in terms of percent. The percent is the vertical change divided by the horizontal change times 100 (to be expressed as a percent): verticalchange *100 = slope% horizontalchange A 25% slope is where the vertical change is 25% of the horizontal change. For example, you 25m move 100 meters horizontally and drop 25 meters: *100 = 25% Note that the 100m percent of a slope is not the angle of the slope. In fact a 100% slope (which is so steep it is difficult to stand upon) is a 45° dip.

Determine relief, grade, and degree of slope at a specific location.

If time, additional activities related to topographic profiles may be added to this lab

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Lab 10.5 Maps of Landscapes For this lab you will need a copy of Laboratory Manual in Physical Geology by Busch and Tasa 5th or 6th edition (Available for loan in class). Find the following maps within and answer the questions below: Map of Waldron Arkansas (pg. 189 6th ed., pg. 181 5th ed.) 1. Describe the overall topography.

2. Explain how the underlying geology determines the topography here. If you have the 6th edition, consult pg. 175, 176 and 184. If you have the 5th edition, consult pg. 166 and 167.

Map of Ennis, Montana (pg. 192 6th ed., pg. 184 5th ed.) 3. Describe the overall topography.

4. What features can be attributed to tectonic uplift?

5. In what ways has erosion shaped this landscape? In what part of the map is most of the erosion occurring?

6. In what ways has deposition shaped the landscape? What features are mostly depositional?

7. What is or has been the major agent of erosion and deposition here (e.g. streams and rivers, glaciers, ocean waves, etc.)? How can you tell?

Map of Glacier National Park (pg. 230 6th ed.) or Map of Siffleur River, Alberta (pg. 213 5th ed.) 8. Describe the overall topography.

9. What features can be attributed to tectonic uplift?

10. In general, is this landscape dominated by erosion or deposition?

11. What is or has been the major agent of erosion and deposition here (e.g. streams and rivers, glaciers, ocean waves, etc.)? How can you tell (besides the name of the park of course… consult the diagrams in Chapter 12 of the 5th ed. or Chapter 13 of the 6th ed.)?

Map of Ocean City, Maryland (pg. 256 6th ed., pg.247 5th ed.) 12. What is or has been the major agent of erosion and deposition here (e.g. streams and rivers, glaciers, ocean waves, etc.)? How can you tell?

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