Earth’s History E.8.7.1-4 Important Vocabulary E.8.7.1-4 1. Igneous 2. metamorphic 3. Sedimentary 4. Rock Cycle 5. Relative age/dating 6. Law of superposition 7. Law of Cross-cutting Relationships 8. Law of Original Horizontality 9. Correlation 10. Index Fossil I Can … – Create a model of the rock cycle and relate the fossil record to how rocks are formed – Construct and analyze scientific arguments to support claims that most fossils provide evidence that life from Earth’s past was diverse and relationships exist from the past to current life forms – Use scientific evidence to create a timelines of Earth’s history that indicates relative dates of strata and the fossils found within the strata using index fossils – Research and provide evidence to document claims about how evolution has been shaped both gradually and through mass extinctions throughout Earth’s varying geological conditions Sedimentary Rocks Igneous Rock Metamorphic Rock How does the Rock Cycle help provide evidence for past life? E.8.7.2 Create a model of the processes involved in the rock cycle and relate it to the fossil record. STEM Careers Associated with Unit – Geologist – Museum director – Paleontologist – Geochemist – Environmental Field – Engineering geologist Technician – Excavator – Drilling Project Manager – NASA Geologist – Field Semiologist – Hydrogeologist 3 Main types of Rocks • Sedimentary • Metamorphic • Igneous Rocks are classified by how they form Igneous Rocks – Igneous rock: forms when molten rock (magma) cools and hardens – 2 types – Classified by where they form – Intrusive – Extrusive Igneous rock locations Intrusive Igneous Rock – Intrusive igneous: cooling of magma takes place slowly beneath Earth’s surface – Rocks are often times very hard and have more colors. granite Extrusive Igneous Rock – Cooling of lava takes place rapidly on Earth’s surface Obsidian Pumice – Rock can either be very light and airy or the rocks can be glassy Metamorphic Rock – Metamorphic rock: forms when any type of rock is changed into a different type of rock – Changes is due to great heat and/or pressure on an igneous or sedimentary rock Gneiss Sedimentary Rock Limestone • Sedimentary rock: forms when sediments (sand, gravel, and dirt) are pressed together over time and become a rock • form in layers. • This process is called lithification • Sediments are: • Rock pieces • Mineral grains • Shell fragments Sedimentary Rocks Limestone Shale Sandstone https://www.pbslearningmedia.org/resou rce/nvmn-sci-grandcanyon/wgbh-nova- making-north-america-uncovering-layers- Granite of-the-grand-canyon/ How do sediments form? weathering – Sediments form through the processes of weathering and erosion of rocks exposed at Earth’s surface erosion Sedimentary Rock con’t…. – Sedimentary rocks can also form from the chemical depositing of materials that were once dissolved in water – When water evaporates, minerals gypsum are left behind and form rock Sedimentary Rocks – Most Fossils are found in sedimentary rocks The Rock Cycle The Earth Recycles Rock – The rock cycle is an ongoing series of processes inside Earth and on the surface – Slowly changes rocks from one kind to another – It is not one continuous circle – Any type of rock can change into another type What drives the Rock Cycle? – Plate movement drives the rock cycle – Subduction (1 plate pushed under another plate) – Re-melts rock into magma – Mountain building – Folding, faulting, uplift – Exposes rock at the surface to be weathered and eroded Copy Me 1. What type of rock will for at #2 in the rock cycle? Review 2. What evidence do you have to support your answer? FOLDABLE TIME How does Rock help provide evidence for Earth’s History? Relative Dating & Fossils E.8.7.1 Use scientific evidence to create a timeline of Earth’s history that depicts relative dates from index fossil records and layers of rock (strata). E.8.7.3 Construct and analyze scientific arguments to support claims that most fossil evidence is an indication of the diversity of life that was present on Earth and that relationships exist between past and current life forms. A Little Bit of History… • The history of geologic time begins with the human interest in mining in the 1500s and 1600s • People began to identify strata (rock layers) by the types of fossils that were found within them. • Two scientists were credited with contributing the most research to this area -- Nicolaus Steno and James Hutton Nicolaus Steno Adapted two geologic principles 1. Law of Superposition : sedimentary rocks are found with the oldest on the bottom and youngest on top. • E.x. Paint layers 2. Principle of Original Horizontality: If left undisturbed rock layers will stay in horizontal order James Hutton 18th-century Scottish physician and farmer . Studied his farm land for geologic changes *The Present is the Key to the Past . Principle of Uniformitarianism: geologic processes from the past are the same as the current geologic processes. E.x. What happened then happens now There are two types of Geologic Dating – Absolute – Determines how many years old something is – Relative – Used to determine if one thing is younger or older than another Tools used to determine Relative Age/dating Absolute Age – Law of superposition – Using radiometric dating – Correlation of rock layers – Use of index fossils Relative Dating – Relative Dating/age is when you give the age of a rock or fossil compared to another rock or fossil. (younger or older) – Example: Rock B is OLDER than Rock A. – An actual age in years is not determined. Rules of Relative Dating 1. Law of Superposition: When sedimentary rock layers are deposited, younger layers are on top of older deposits. – Fossils are generally the same age as the rock layers in which they are found – Animal remains are deposited along with the sediments that will turn into sedimentary rocks Rules of Relative Dating 2. Law of Original Horizontality: Sedimentary rock layers are deposited horizontally. If they are tilted, folded, or broken, it happened later. Law of Original Horizontality Rules of Relative Dating 3. Law of Cross-Cutting Relationships: If an igneous intrusion or a fault cuts through existing rocks, the intrusion/fault is YOUNGER than the rock it cuts through – What is “B”? – Place the layers in order from oldest to youngest Unconformity – Unconformities- breaks in geologic time where rock layers erode away or when sediment isn’t deposited – a new rock layer can formed atop an eroded surface – rock has been eroded, so you have a missing section of time in the rock record. Unconformity – What section of time is missing? Angular Unconformity • What events What type of might have What caused the rocks formed caused the rock angular unconformity? above? layers to become tilted? • Why is the top flat? Angular Unconformity Correlation – Rock layers in different places can be correlated or matched up by matching up the rocks and fossils in the layers. 1. Which layers Correlate? 2. What does that mean about those layers? 3. Are there any areas of unconformity? https://youtu.be/sgPnnzou0og America Museum of natural History https://www.youtube.com/watch?v=9f5HehQovx8 Paleontology . The study of fossils . Fossils Records are the history of life as documented by all fossils ever found on Earth What kinds of rocks are most fossils found in? What is a fossil? • A fossil is the preserved remains of a once- living organism. What do fossils tell us? • Give clues about organisms that lived long ago • Help to show that evolution has occurred. • Provide evidence about how Earth’s surface has changed over time. • Help scientists understand what past environments may have been like. •Marine fossils indicate a marine environment •wooly mammoths indicate a cold environment HOW IS A FOSSIL FORMED? – 1. Sediment – An animal is buried by sediment, such as volcanic ash or silt, shortly after it dies. Its bones are protected from rotting by the layer of sediment. – 2. Layers – More sediment layers accumulate above the animal’s remains, and minerals, such as silica (a compound of silicon and oxygen), slowly replace the calcium phosphate in the bones. – 3. Movement 1.– SedimentMovement of tectonic plates,2. or giantLayers rock slabs that make up Earth’s3. Movement surface, lifts up the sediments4. andErosion pushes the fossil closer to the surface. An animal is buried by More sediment layers Movement of tectonic Erosion from rain, sediment,– 4. Erosion such as accumulate above the plates, or giant rock rivers, and wind wears volcanic ash or silt, animal’s remains, and slabs that make up away the remaining rock – Erosion from rain, rivers, and wind wears away the remaining rock layers. Eventually, erosion or people digging for fossils shortlywill after expose it dies. the preserved Its remains.minerals, such as silica Earth’s surface, lifts up layers. Eventually, bones are protected (a compound of silicon the sediments and erosion or people from rotting by the and oxygen), slowly pushes the fossil digging for fossils will layer of sediment. replace the calcium closer to the surface. expose the preserved phosphate in remains. the bones. FIVE MAIN TYPES OF FOSSILS Petrified Molds and Carbon Fossils Casts Films Trace Preserved Fossils Remains PETRIFIED FOSSILS • The word “petrified” means “turning into stone.” • Form when minerals replace all or part of an organism. PETRIFIED FOSSIL The Field Museum in Chicago displays a fossil of a Tyrannosaurus rex. MOLDS AND CASTS • A mold forms when hard parts of an organism are buried in sediment, such as sand, silt, or clay. MOLD FOSSIL This mold, or imprint, is of •Hard parts completely dissolve over time, leaving an extinct mollusk called behind a hollow area with the organism’s shape. an ammonite. • A cast forms as the result of a mold. •Water with dissolved minerals and sediment fills the mold’s CAST FOSSIL This ammonite cast was •Minerals and sediment that are left in the mold discovered in the United make a cast.