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Name: Class Set Quiz Date: Per: Updated 3-22-13 This material can be found in the Catastrophic Events book (pages 198-273) and in your ScienceSaurus (topics 179-197). Good BrainPOPs to watch on this topic include: Volcanoes, Rock Cycle, Types of Rock, Weathering, Erosion and Mountains. There are also some PowerPoint presentations that we have been looking at in class on Mr. Abe’s website. Types of Volcanoes (Lesson 20): Focus Question: What are the 3 main types of volcanoes and what are their properties and examples? -Stratovolcanoes are large layered volcanoes with sticky gassy (high viscosity) magma that results in short explosive eruptions that result in major devastation to the landscape. Stratovolcanoes are located at subduction zones (convergent plate boundaries) and form the “Ring of Fire”. Examples include Mt. St. Helens, Mt. Rainier, Mt. Fuji, etc. -Shield volcanoes are wider than they are tall (flat) volcanoes with very hot runny (low viscosity) magma that result in slow oozing eruptions that can last a long time. Shield Volcanoes form at hotspots that can be located at a plate boundary (like Iceland) or way out in the middle of a plate (like Hawaii). -Cinder Cone Volcanoes are smaller volcanoes that have hot gassy magma that result in small explosive eruptions that can last for a fair amount of time. Cinder Cone Volcanoes can be found near other volcanoes (like Wizard Island, Crater Lake) or in areas where no volcanic activity had previously occurred (like Paricutin, Mexico). Magma and Lava Lab (Lesson 19): Focus Question: How do magma and lava change the surface of the Earth? -Magma can have different viscosities based on many factors including its temperature. -The hotter the magma the lower the viscosity. This would be like the runny magma of a shield volcano. -The cooler the magma the higher the viscosity. This would be like the more sticky magma of a stratovolcano. -Magma with higher viscosity creates earthquakes as it pushes its way up through the crust. Often times the magma won’t reach the surface and create a lava dome (a bump with cracks) as a result. -Hotter magma with lower viscosity burns through the crust and runs on the surface until it pools and cools or comes in contact with water and cools. This would create the layers of volcanic rock or pillow lava (like Hawaii). -Sometimes the magma leaves the magma chamber and the top of the volcano collapses making a special landform called a caldera (Crater Lake). -As magma and lava make their way to the surface and cool they form new landforms and new rock to build up the Earth’s crust. Lahar Lab: Focus Question: What story can layers of rocks tell us about the landscape? -The Principle of Superposition tells us that the older rock layers are on the bottom and the newer rock layers are on the top. This can help us find the relative ages (newer than, older than) of the rocks. -A lahar layer tells us there was a landslide caused by a volcanic eruption, earthquake, flooding or some other major event. -A tephra (ash) layer tells us there was a major volcanic eruption and the type of ash can tell us which volcano it came from. -The layers of an area can tell us about the geologic history of that region. The rocks tell us the story of the landscape. Newest Rock Oldest Rock Igneous Rock Lab (Lessons 21 and 22): Focus Question: What story can individual rocks tell us about the landscape? -Minerals are the ingredients that make up rocks. We can learn where a rock could possibly be from based on the types of minerals in the rock. -A clump of minerals is called a crystal. Sometimes crystals have very specific patterns and those patterns help us identify the crystals. -Rocks that cool quickly have small crystals. Rocks that cool slowly have larger crystals. -If a rock has small crystals we can infer that the rock was probably lava that cooled quickly on the surface. We call these rocks extrusive rocks (extra=beyond/outside). -If a rock has large crystals we can infer that the rock was probably magma that cooled slowly inside the earth. We call these rocks intrusive rocks (in=inside) Rock Cycle Online Activity: Focus Question: What are the types and properties of the three main types of rocks and how can they change from one type to another? -Sedimentary rocks are rocks that are made from layers of sediment (sand, pebbles, shells, etc) that build up and then undergo compaction and cementation to form rock with layers. -Igneous (fire) rock is formed when magma or lava cools to form a rock. -Metamorphic rock is rock that is formed when igneous or sedimentary rock are introduced to intense heat or pressure and changed. Metamorphic might have layers and crystals that are warped. -Weathering and erosion can break all 3 types of rocks down into sediment. -Plate tectonics can push all 3 types of rock into the mantle to melt back into magma. -Take a look at the rock cycle diagram on page 250 in your Cat. Events book or page 180 in your ScienceSaurus or head back to the interactive activity at http://www.learner.org/interactives/rockcycle/index.html The Principle of Super Position and Unconformities: Focus Question: What things can happen to change the stories of the rocks? -The Principle of Superposition tells us that the older rock layers are on the bottom and the newer rock layers are on the top. This can help us find the relative ages (newer than, older than) of the rocks. -Unconformities are changes that occur in the rock layers (strata). -Unconformities can be caused by plate tectonics (earthquakes), volcanic activity (magma pushing and lava flows), erosion (water and glaciers), lack of deposition (no new sediment is deposited over a long period), etc. -Unconformities can add rock layers (add chapters), shift rock layers around (rearrange chapters), erase or delete rock layers (delete chapters) or maybe there is just a long period of time where there were no layers deposited (no middle chapters written). Weathering and Erosion: Focus Question: What processes break down the earth’s crust? -Weathering and erosion can be mechanical or chemical. -Mechanical erosion is when the rock is broken down by water, wind, sand, freezing and cooling, glaciers, living things like tree roots, etc. -Chemical erosion occurs when the rocks react with chemicals and are broken down. Some examples are acid rain and oxidation (like rusting). -In either case rocks are broken down smaller and smaller until they form sediment and then can be changed back into sedimentary rock by compaction and cementation. Hint, Hint, Wink, Wink Question: Explain the processes that can change the three main types of rock into another type of rock. Be sure to include the names of the three types of rock. http://www.learner.org/interactives/rockcycle/index.html Other Stuff: (Information learned from BrainPOPs and other activities.) -Living things also play a role in the story of rocks and rock formation. -Fossils are traces of organisms that are preserved as rocks. They can not only tell us what living things were living in the area, but also provide us clues about the climate and other conditions of the past. Fossils can also help us find the age of rock layers if we know the relative age of when the organisms were on earth we can infer that the rocks are about the same age. -Coal is formed from swamp plants that decay into peat. Peat can then be compressed and turned into rock (coal). A coal deposit in the landscape would suggest that at one point there was a swamp-like habitat. -Coral is the “skeleton” that the actually little animal corals build to attach themselves to. Minerals from the water are used for the coral. Finding coral suggests that there was a warmer body of salt water at one point. (Usually coral grows in present day tropical oceans.) -Limestone is formed by the shells of marine invertebrates piling up layer after layer and compressing into rock. There is a great deal of Calcium and Carbon that make up the shells of these marine invertebrates. Limestone deposits suggest that there was a large body of salt water at one point. -The K-T Boundary is a rock layer that was deposited about 65 million years ago. There are higher levels of a radioactive element called iridium in the rock. It is thought that the rock that makes up the K-T boundary was deposited when a giant asteroid hit the earth kicking up a dust cloud so big that it settled over the entire Earth. A huge crater that is also dated to about 65 million years ago was discovered off of the Yucatan Peninsula of Mexico. It is widely accepted that this asteroid impact is what killed off about 90% of all species on Earth including dinosaurs. Dinosaur fossils are found below the K-T Boundary but no dinosaur fossils are found above the K-T Boundary. -Volcanologists (scientists that study volcanoes) can make short term predictions of volcanic eruptions by looking at the number of earthquakes near the volcano. As magma pushes its way up to the surface there is pressure that builds and then eventually the rocks break. This leads to a much higher frequency of earthquakes under the volcano. Before the eruption of Mt. St. Helen’s there was also a large bulge (lava dome) that was growing on the North side of the mountain as the magma rose. This gave anyone that wanted to time to evacuate to safety and no one was surprised by the eruption.