Where Plates Collide A subduction zone also can form where two oceanic plates converge. In this case, the colder, denser oceanic plate bends and sinks down into the mantle. Mariana Islands in the western Pacific are a chain of volcanic islands formed where two oceanic plates collide. Usually, no subduction occurs when two continental plates collide, as shown in the previous diagram. Because both of these plates are less dense than the material in the asthenosphere, the two collide and crumple up, forming mountain ranges. Earthquakes are common at these convergent boundaries. However, volcanoes do not form because there is no, or little, subduction. The Himalayas in Asia are forming where the Indo-Australian Plate collides with the Eurasian Plate. Where Plates Slide Past Each Other The third type of plate boundary is called a transform boundary. Transform boundaries occur where two plates slide past one another. They move in opposite directions or in the same direction at different rates. When one plate slips past another suddenly, earthquakes occur. The Pacific Plate is sliding past the North American Plate forming the famous San Andreas Fault in California, as seen the figure to the right. The San Andreas Fault is part of a transform plate boundary. It has been the site of many earthquakes. 1.) Plates Moving Apart The boundary between two plates that are moving apart is called a divergent boundary What forms when two plates move apart? 1. Rift Valleys http://www.uoguelph.ca/geology/geol2250/glossary/HTML%20files/DRC%20Great%20Rift%20Valley.jpg 2. Ocean Ridges * Magma from these ridges forms new ocean crust 2.) Plates moving together • Plates move together at convergent boundaries • When an oceanic plate meets a continental plate the oceanic plate subducts, or goes down, into the mantle. • What forms when two plates converge? * Volcanoes (oceanic and oceanic) * Deep sea-trenches (continental and oceanic) * Mountain ranges (continental and continental) 3.) Plates sliding past each other • Transform boundaries occur where two plates slide past one another. • What occurs when one plate slips past another suddenly? EARTHQUAKES This is what is happening in California at the San Andreas fault (Figure 11 on page 404) Review: What are the 3 ways plates move? • Apart at divergent boundaries • Together at convergent boundaries • Past each other at transform boundaries In your notebook, answer the following questions: Between what two plates is there a convergent boundary? Between what two plates is there a divergent boundary? Between what two plates is there a strike-slip (transform) boundary? Picture of the Major Plates of the Earth: page 401 http://en.wikipedia.org/wiki/Plate_tectonics Science Notebook Number your paper 1 thru 7 and use each of the following vocabulary in a complete sentence: 1.Crust 2. mantle 3. inner core 4. outer core 5. asthenosphere 6. lithosphere What do you think happens when plates move? Catastrophes! Can you give some examples of catastrophes? A catastrophe is a major event of destruction. k •EaRthQua es • Tsunamis We are going to learn what happens when the Earth’s plates move. It might get dangerous! http://www.brainpop.com/search/index.weml?k eyword=earthquakes Tsunami • http://www.brainpop.com/science/earthsystem/tsunami/ Do you want to draw? Too bad if you don’t, you are about to become an artist Continental Drift This is the belief that the continents were all connected into one large landmass. Does anyone know what this one large landmass was called? Pangaea Let’s look at the first map in your packet. Do you see how if we cut them out, they would sort of, kind of fit together? It would not be a perfect fit, but they would come close. Let’s see if it works! Get out your packet. Find the blank world map. Instructions Cut out each of the pieces from Pangaea. Place them on the correct continent that they would represent today. Once you have placed them where you think they belong, RAISE your hand so that I or a classmate can verify your answers. Once you have correctly placed ALL 7 continents you need to glue them to the World Map and LABEL the continents correctly. When you have completed the activity, you may turn in your completed map. You MUST clean up your area. ALL scraps of paper MUST be put into the trash, glue and scissors MUST be returned to their proper places. Pangaea…again Remember learning about Pangaea and the continental drift? Let’s go back and see what supports the belief that all continents were once connected. Turn to page 392 in your OLD science book. Alfred Wegener • A German meteorologist who made the hypothesis that the continents were once all connected as one large landmass (Pangaea). However, over time the continents have slowly moved to their current location. What Is the Evidence Wegener Used to Support His Hypothesis? • Turn to page 393 Evidence • Fossil Clues (Read page 393 – old book) • Climate Clues (Read page 394 – old book) • Rock Clues (Read page 394 – old book) But How Did the Continents Move? • He couldn’t explain it! • But others did. Sea Floor Spreading What do you think that means? How do we know what the seafloor looks like? Let’s read about this on page 396 of the OLD text book. Seafloor Spreading • Seafloor spreading is when hot, less dense material below Earth’s crust rises toward the surface at the midocean ridges. Then, it flows sideways, carrying the seafloor away from the ridge in both directions Let’s Read Turn to page 397 in the old green textbook Review • Once we have completed the reading in the OLD text book you need to answer the Section Assessment questions, 1 – 5 on your own paper. Landforms What do you know about landforms???? Landforms Landforms are natural features of the landscape, natural physical features of the earth's surface. What are some of the landforms you know? Valleys From this picture, what do you think a valley is? A VALLEY is a hollow or surface depression of the earth bounded by hills or mountains, a natural trough in the earth's surface, that slopes down to a stream, lake or the ocean, formed by water and/or ice erosion. Plateaus A PLATEAU is a large highland area of fairly level land separated from surrounding land by steep slopes. Some plateaus lie between mountain ranges. Others are higher than surrounding land. MoUnTainS Mountains Over long periods of time, mountains are created by tremendous forces in the earth with a steep top usually shaped up to a peak or ridge. Mountains occur more often in oceans than on land; some islands are the peaks of mountains coming out of the water. Mountains are formed by volcanism, erosion, and disturbances or uplift in the earth's crust. Turn to page 407 in the OLD text book and let’s read about Mountain formation and volcanoes. Brainpop Video • Mountains • http://www.brainpop.com/ Plains Plains are broad, nearly level stretches of land that have no great changes in elevation. Plains are generally lower than the land around them Hills Hills are elevations of the earth's surface that have distinct summits, but are lower in elevation than mountains Glaciers A GLACIER is a huge mass of ice that flows slowly over land. They form in the cold polar regions and in high mountains. Brainpop Video • Glaciers • http://www.brainpop.com/ Let’s see if you can pick out specific landforms. 1. Get out a sheet of paper. 2. Look at the picture on the screen. 3. Write which landform you think it is. What else do you think can cause the surface of the Earth to change forms other than what we have already talked about? An Asteroid • What are some characteristics of an asteroid? In other words, what makes an asteroid an asteroid and not something else. Asteroids • Asteroid - Any of numerous small celestial bodies that revolve around the sun, with orbits lying chiefly between Mars and Jupiter and characteristic diameters between a few and several hundred kilometers More Catastrophes • What do you think would happen if an Asteroid hit the Earth? • http://www.pbs.org/wgbh/nova/sciencenow/ 3313/01.html What is the difference between an asteroid an a comet? What do you think? COMET Comets - are distinguished from asteroids by the presence of a tail behind them. Comets are thought to consist chiefly of ammonia, methane, carbon dioxide, and water. Haley’s Comet (2061) Let’s read about Haley’s Comet Who is Haley anyway? http://www.associatedcontent.com/article/796 7/halleys_comet_through_history.html Weathering Who can tell me what weathering is? Weathering Weathering breaks down and loosens the surface minerals of rock so they can be transported away by agents of erosion such as water, wind and ice. Nearly all weathering involves water, mostly from: frost shattering, wetting and drying, and salt weathering What do you think happens because of weathering? United Streaming Video • Weathering • http://streaming.discoveryeducation.com/ • http://player.discoveryeducation.com/index.cf m?guidAssetId=F3E2749C-D871-4EBA-930FF30574A4CF79&blnFromSearch=1&productco de=US Frost Shattering The force of water in rock fractures as it freezes and expands, or is forced into the rock by the pressure of freezing water Sandstone, shattered by frost action. Salt Crystallization It causes disintegration of rocks when saline or salt solutions seep into cracks and joints in the rocks and evaporate, leaving salt crystals behind. These salt crystals expand as they are heated up, exerting pressure on the confining rock. Salt Crystallization Salt Crystallization Water When rock minerals take up water, the increased volume creates physical stresses within the rock. Water Erosion What do you think EROSION is? Erosion The movement of soil from one place to another. Let’s look at page 72 in your NEW science book. This is about erosion and weathering. We know that rock can erode. What else can erode? Let’s look at page 574 in your new text and find out. Soil Erosion Law of Superposition and Fossils Open your CCT Coach book to page 114 and let’s read about Law of Superposition and Fossils. Law of Superposition In a bed of undisturbed layered, sedimentary rocks, the rocks on top are younger than the ones below. The oldest sediments must be laid sown before the younger ones pile up on top. Fossils The imprints of remains of once-living things often preserved in sedimentary rocks. Brainpop Video & Quiz (Fossils) • http://www.brainpop.com/science/diversityof life/fossils/ Trace fossils • Fossilized impression made by an organism (plant or animal) in a substrate (sand, soil, or clay) • They include footprints, burrows, feeding marks, dragging tails, and Mold fossils Mold fossils are created when the organism leaves and imprint of itself in the substrate. It is similar to having a picture of the organism without having any remains of the organism. Cast fossils Cast fossils are created when a Mold Fossil of an organisms is filled with a substrate like sand, soil, or clay. The cast is like having a model of the organism without having any remains of the organism. Petrifaction The process by which organic material is converted into stone or a similar substance. It is approximately synonymous with fossilization.