Objective: Grade: 6 Students will learn the underlying cause of earthquakes and how they shape the Subject Areas: Art, Earth science, land. They will model types of faults. Geography, Physics

Skills: classifying, Materials describing, identifying, • pictures of earthquake • manipulatives representing observing, modeling, faults buildings, etc. (optional) questioning • earthquake squeeze box • map showing Mendocino • 5 lbs of colored sand Triple Junction Duration: 1 hour • 3 lbs of flour • cameras for before and after • 3 lbs of potting soil photos Connections: • modeling clay of • computer with internet and geology, engineering, different colors projection capabilities oceanography, landforms, • rollers for rolling clay history • wooden 2x4 blocks (2 per student) Vocabulary crust Standards Strands: Excellence in Environmental Education Guidelines fault Strand 1 —Questioning and Analysis: F) Working with models and creep simulations: Learners understand many of the uses and limitations of models. Strand 2.1 —The Earth as a Physical System: A) Processes that shape the Earth: strike-slip fault Learners have a basic understanding of most of the physical processes that shape normal fault the Earth. They are able to explore the origin of differences in physical patterns. reverse fault California State Educational Standards: Earth Science (ES) 1: Plate Tectonics and Earth’s Surface: 1a: Students know the epicenter evidence of plate tectonics is derived from the fit of the continents; the location of Mendocino Triple Junction earthquakes, volcanoes, and mid-ocean ridges; and the distribution of fossils, rock types, and ancient climatic zones. Richter Scale ES 1d: Students know that earthquakes are sudden motions along breaks in the crust called faults and that volcanoes and fissures are locations where magma Mercalli Intensity Scale reaches the surface. 1e: Students know major geologic events, such as earthquakes, liquefaction volcanic eruptions, and mountain building, results from plate motions. ES 1f: Students know how to explain major features of California geology (including mountains, faults, volcanoes) in terms of plate tectonics. Earth Science (ES) 2: Shaping Earth’s Surface: 2d: Students know earthquakes, volcanic eruptions, landslides, and floods change human and wildlife habitats. Background

involved are applied: strike-slip, to slip downward compared to the Shaking Earth normal and reverse. other block. The series of basins and ranges of central Nevada represent here are few things scarier, if you A strike-slip fault is when two rock a large area of crustal extension. Tlive in California, than a large blocks move past each other. The San With the onset of crustal extension, earthquake. Earthquakes are common Andreas Fault may be the most famous great blocks of earth dropped down here because of numerous faults strike-slip fault. The great earthquake along normal faults, forming the long including the San Andreas Fault, a of 1906 caused the San Andreas fault valleys that we see today. Lastly, there very large active fault that extends to rupture along almost three hundred are reverse faults or thrust faults north-south through the state. Most miles. In some places, the offset was caused by compression forces or forces earthquakes are the result of quick almost 30 feet. A normal fault is pushing towards each other. When movements along a fault, however, when the crust is being stretched this happens one rock block is forced any force large enough to send a apart. This causes one rock block upwards and over the other rock wave through rock will register on a seismograph, the main instrument that measures them. If you could look at a cross section of Local the Earth’s interior, you would see the top of the planet is a relatively Connection thin layer of solid rock. This surface is called the crust. For reasons still not The northern California coast is one of the most tsunami-prone understood, the crust is broken up into areas in the world. Tsunamis are a series of sea waves that originate sections or plates. Below the crust is in the sea and are usually caused by earthquakes beneath the sea hot molten rock that moves the plates floor. The first wave to arrive is not always the most dangerous. The as if they are riding on a conveyor waves can travel up to speeds as fast as 600 miles per hour and the belt. The shifting of these plates series of waves can last for hours. causes major geologic events such The word tsunami is Japanese in origin. Tsunami literally means as mountain building and volcanic “harbor wave”. Tidal wave is another term given to these waves eruptions. As the plates move, the rock except it is misleading. Tides do not cause the phenomenon, they are made of fractures due to the although they can influence the size of the waves. Furthermore, stresses this motion causes. scientists often refer to tsunamis as seismic sea waves, however, tsunamis can be caused by underwater landslides and meteorite A fault is a region where blocks of impacts, not just earthquakes. rocks or plates move relative to each One of the worse tsunamis ever recorded along the coast of other. They are basically fractures California happened in 1964. It was caused by a 9.2 earthquake that can range from millimeters to off the coast of Alaska. The waves radiated outwards and travelled thousands of kilometers long. The down the coast of California hitting the hardest at the town of San Andreas fault is roughly 1280 Crescent City north of Eureka. kilometers or 800 miles long and is Because of the threat these unique waves cause to life and property, where the Pacific plate is grinding past early warning systems have been set up around the Pacific basin the North American plate. Sudden and elsewhere. If someone experiences an earthquake while in a movement along a fault causes an coastal area, they are advised to reach for higher ground as soon as earthquake. Slow movement along a possible. Once the shaking stops, a person should try and get to an fault is called creep. area that is at least 100 feet above sea level and 2 miles inland. There are three main types of faults depending on the direction the forces

Lost Coast Environmental Education Resource 2 block. These are the common types of feet above sea level stranding the faults in Mendocino and Humboldt Measuring Shakes organisms living in the tidal zone counties where the Juan de Fuca and there. This was just one example Gorda plates are colliding with the of a localized uplift event causing North American plate. This motion Earthquakes are measured a lot of a terrace. There is now evidence continues to create a broad region different ways. The Richter Scale showing several events like this have of crustal compression resulting in is a logarithmic scale from 1-10 and happened repeatedly along the Lost folding and thrust faulting. Areas is most commonly used. Most people Coast in the past causing geographic where the crust is being compressed can’t notice earthquakes under 4 stair steps or terraces where the may experience rapid rates of uplift as on the Richter Scale. The difference relatively flat seafloor is uplifted above the crust buckles upwards. in ground motion between two sea level. Various events can be dated consecutive numbers on this scale (like using the remains of stranded marine The movements of crustal blocks past 6 and 7) is ten times greater. However, organisms such as attached mussel one another along a fault is typically the amount of energy released is shells, barnacles and clam shells not smooth and gradual. When thirty times greater compared. The preserved in place. The higher the the fault cannot allow for smooth energy released from an earthquake ancient marine terrace, the older it is. slippage of crust past one another, measuring 7 on the Richter Scale is Other features created by local uplift strain accumulates. When the strain equal to 475,000 million tons of TNT events include the flat landscape on is suddenly released, an earthquake whereas one measuring 4 on this scale the western end of Shelter Cove, many results. Most of the time, the released is equivalent to a mere 15 tons of TNT. parts of the Lost Coast Trail from the energy is small and barely noticeable. The Mercalli Intensity Scale is Mattole River south to Shelter Cove, The exact location of the earthquake more subjective than the Richter Scale. and the excellent surfing location at is known as the epicenter. Most It measures the amount of damage Big Flat north of Shelter Cove. Good earthquakes occur several miles done to buildings and other structures surfing is possible at Big Flat and other underground. like bridges. The scale ranges from I locations along the Northcoast because (detectable only by instruments) to the waves break offshore due to reefs The west coast of the United States XII (total destruction). Many buildings that have been uplifted into shallow is famous for earthquakes due to will begin to experience damaging water and have not yet had a chance to numerous faults. The Mendocino effects at an intensity level of around erode. Triple Junction (MTJ) is an area VII on the Mercalli Intensity Scale. adjacent to the King Range Natural In other areas, particularly further Conservation Area (NCA) near Cape The amount of damage caused to north around the Eel River and Mendocino. It is the most seismically buildings is dependent largely upon Humboldt Bay, the land may rapidly active region in North America. The the type of rock or sediments they are subside allowing ocean water to MTJ is where three plates merge. It is built upon. Usually major damage intrude inland and flooding coastal rare to have three plates converge so to buildings in places with strict lowlands. Large earthquakes may close to a shoreline. The Pacific Plate building codes like the United States also generate giant landslides, is heading in a northwest direction occur with earthquakes measuring reshaping entire mountainsides in an while the North American Plate 6.2 and above. If the area is a filled in instant. This area apparently has had is moving in a southeast direction wetland, tidal flat, or some other area extremely powerful earthquakes in the along the San Andreas fault. A small made of loose sediments, the ground past, most likely exceeding magnitude remnant of a once larger plate, the movement may cause what is called 8 and possibly magnitude 9 on the Gorda plate, is colliding with North liquefaction. This phenomenon Richter Scale. America and submerging below changes the behavior of seemingly the North American plate along the solid ground to act like a liquid and Cascadia Subduction Zone. Finally, can cause severe damage. Individual the Pacific and Gorda plates grind past earthquakes have played a role in one another in an east-west direction shaping the landscape around us. In along the Mendocino Fracture Zone. 1992, just north of the King Range The combination of all these plate NCA, a series of three relatively large movements and resulting faults, earthquakes occurred measuring causes this area of the coast ranges to 7.1, 6.6, and 6.7 respectively. This lift, twist, rattle, and roll. event lifted the intertidal zone four

Lost Coast Environmental Education Resource 3 Activity: Modeling Earthquake Faults

Preparation For the first demonstration, place at least three different layers of soil, flour and colored sand in the earthquake squeeze box. Pat down Materials firmly. (See 1st procedure.) Check to make sure the school’s computer • modeling clay of system will allow you to open up: http://earthquake.usgs.gov/ for different colors later use. • rollers for rolling clay • wooden 2x4 blocks (2 per student) Procedure • manipulatives 1. Explain to the students that representing models can help us learn about buildings, etc. earthquakes and the faults that (optional) • Has anyone here ever felt cause them. Model the earthquake • map showing an earthquake? in a box. (See photo.) Gently press Mendocino Triple • Has anybody ever the two side panels together. (A Junction been scared during an few faults should form.). Use this cameras for before earthquake? model to introduce faults. • and after photos • Who knows what causes computer with earthquakes? 2. Write down a KL (Know and • internet and • What do you know about Learn) chart on the board or local geology? overhead projector. Ask students projection capabilities • Does anyone know a questions about earthquakes.Write famous fault? down student responses into the • What happens along correct category: K is what they faults? already know and L is what they 5. While the students are want to learn more about. • Does anyone know a the exploring independently, log onto name of a type of fault the website below to prepare to 3. Show the map of the Mattole that causes earthquakes? show them images: Triple Junction and other pictures. • What types of damage do http://earthquake.usgs.gov/learn/ Explain that this area is very earthquakes cause? faq/?faqID=55 seismically active. Briefly discuss • How do we measure the San Andreas Fault and the earthquakes? 6. Have everyone stop moving local geology of the region. • Can we predict their blocks to continue with the earthquakes? next step. Write down the three 4. Next, hold up two wooden • What would you like different types of faults and the blocks and explain to them that to know more about in different directional forces (using they will be using these to model regards to earthquakes? arrows) for each. faults. Explain to the students that Do you think we know • the wooden blocks represent huge (Activity continued on next page.) everything there is to blocks of rock. You may want to know about earthquakes? ask them if they think rock is very flexible. Have them investigate using the blocks to figure out how many different ways two blocks can move relative to each other. Pass out the wooden blocks. Give them a few minutes to explore.

Lost Coast Environmental Education Resource 4 Activity Continued

inch thick. 7. Project the webpage showing 9. Have them place the clay the animations of the various types layer on top of two blocks of of faults. Explain to them that once wood touching each other so they they see an animation they should lay flat. To this basic clay layer, model the same type of movement students can add manipulatives with their blocks of wood. Have (wooden splints, monopoly pieces, them model the three types of etc.) or use different colors of faults a few times. The animations clay to make features they want move quickly. If a computer is not in their landscapes (house, trees, available, you can model the three river, etc.). They are to model an types of faults with them, or they active transform fault by moving can use a handout as a reference. the blocks in opposite directions (apply shear force). 8. Lastly, have them model the affects of a transform fault on a 10. Taking pictures before and landscape. This activity will take after may be a fun alternative. the longest. Remind them that this If time allows, they can model is the common type of fault locally. another type of fault or draw their To do this, they need to first roll landscape before and after the out clay using wooden rollers. The mock earthquake. layer of clay should be about 1/4

Extensions • Connect earthquakes and faults to other Earth Science topics like mining and volcanoes. • Have students perform online research about famous earthquakes around the world and then have them write a paper about one of them. • Have students plot the epicenters of recent earthquakes or large earthquakes on a map. • Use the radii from three or more seismograph stations to find an epicenter. • Get a seismograph or meter at the school site for ongoing record keeping. Information available at www.iris.edu/hq/programs/ • Check out: Table Top Earthquakes from USGS: http://jclahr.com/science/earth_science/tabletop/ for a host of activities. • Other sources: Living on Shaky Ground, www.humboldt.edu/shakyground/, Humboldt State University Northern California Earthquake Data Center, www.ncedc.org/ http://www.earthscope.org/ References Animations: http://earthquake.usgs.gov/learn/faq/?faqID=55 Chart from : http://www.matter.org.uk/schools/content/seismology/richterscale.html, 2010 King Range National Conservation Area Draft Resource Management Plan and Draft Environmental Impact Statement, U.S. Department of Interior, BLM, Arcata Office, Jan. 2004 Living on Shaky Ground, http://www.humboldt.edu/shakyground/, Humboldt State University, 2010 The San Andreas Fault, http://spacedaily.com/, 2010 Tsunamis, http://www.ess.washington.edu/tsunami/toc.html USGS FAQs: http://earthquake.usgs.gov/learn/faq/, 2010

Lost Coast Environmental Education Resource 5 From BLM

Lost Coast Environmental Education Resource WS1 Name: Date:

Fault Predictions

Record your observations in the space below.

Hypothesis Result (what you think (what actually will happen) happened)

Strike-Slip Fault

Reverse Fault

Thrust Fault

Lost Coast Environmental Education Resource WS2