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The Geosphere Lesson 3 Lesson 3 QUESTION: Alfred Wegener (a German scientist) asked a question; Do the coastlines of continents separated today show evidence that they once matched? If we went around the world and looked at all of the coastlines (on different continents) would we see things that would make us believe they used to fit together (the continents). ANSWER: Yes, they do. Wegener (and other scientists) found matching animal fossils on coastlines of different continents and also matching geologic structures on different continents. From that discovery he developed the: “Theory of Continental Drift” Wegener proposed the idea that once upon a time all of the continents fit together like a puzzle, and were one massive continent called: Pangaea http://www.historyforkids.org/scienceforkids/geology/platetectonics/ Use the graphic organizer on “Discover” pg. 1 under the “Continental Drift” tab to organize the information in the lesson: **Use the letter Alfred Wegener wrote to fill in the organizer (on the same page). Continental Drift Continental Drift Continental Drift In the beginning Wegener was wrong about “how” the plates moved from Pangaea to what we see today. He later he developed a new idea called: The Theory of Plate Tectonics The Theory of Plate Tectonics Use the interactive on “Discover” pg. 2, under the “Plate Tectonic Theory” tab to investigate the evidence Wegener used to develop this theory. Plate Tectonics Plate Tectonics Plate Tectonics Plate Tectonics Plate Tectonics What’s the difference between them?! Hotspots helped to support the theory of plate tectonics. The plate moves (very slowly) over a “plume” which is releasing magma. As it cools it forms chains of islands. What makes the plates move? What makes the plates move? “The asthenosphere of Earth acts like a conveyor belt moving slabs of lithosphere.” “Plates on Earth move as a result of convection deep within Earth. Convection in the mantle of Earth results from the rising of hot rock material and the sinking of cooler rock material. The constant rise and fall of material leads to the formation of convection cells.” Complete the interactive on “Discover” pg. 2 “Mechanisms of Movement” tab. Convergent Boundary • What happens with this type of plate movement? Convergent Boundary The plates come together… converge. This creates: Convergent Boundary The plates come together… converge. This creates: MOUNTAINS or TRENCHES Divergent Boundary What happens with this type of plate movement? Divergent Boundary Plates move apart. …diving away from each other. Divergent Boundary Plates move apart. …diving away from each other. This creates: New crust is formed A fault. When the plates move horizontally (one moves one way the other moves the opposite). What to do; Lesson 3 What to do; Lesson 3 What to do; Lesson 3 What to do; Lesson 3 Lesson 4 Lesson 4 The landscape of the Earth is formed and re-formed over time. There are things that can impact the geosphere and change it, such as: Erosion • • • • Wind Water Freezing Gravity Earth's surface has interlocking plates known as tectonic plates, or lithospheric plates. “The movement of the plates breaks the crust in various locations known as faults. A fault can, but does not necessarily, indicate the edge of a tectonic plate.” Movement of Faults The place where two segments of Earth’s crust come in contact with each other at a fault is called the fault plane. The fault plane is usually at an angle. The hanging wall is the block of rock above the angle of the fault plane. The footwall is the block of rock below the angle of the fault plane. (*The location of the fault plane determines how each side of the fault is named.) Movement of Faults Normal Faults Reverse Faults Strike-Slip (Lateral) Faults Movement of Faults Normal Faults Normal faults form as two segments of crust pull away from each other at divergent plate boundaries. The hanging wall drops down relative to the footwall, or the footwall moves up relative to the hanging wall. Normal faults form as a result of a type of stress known as tension stress. Movement of Faults Reverse Faults Reverse faults are also known as thrust faults. These faults occur along convergent plate boundaries, where lithospheric plates come together. In a reverse fault, the hanging wall is “thrust” up—that is, it moves up relative to the footwall. Reverse faults form from a type of stress known as compression stress. Movement of Faults Strike-Slip (Lateral) Faults Strike-slip faults, also known as lateral faults, occur where two blocks of crust move past each other in opposite directions. Strike-slip faults are common along transform plate boundaries, where tectonic plates slide past each other. Strike-slip faults form from a type of stress known as shear stress. Mountains Mountains result (are formed) from the movement of tectonic plates. Mountains result (are formed) at divergent and convergent boundaries. There are different types of mountains that can form... VOLCANOES Forms when lava or ash build up to form into a mountain. FOLDED MOUNTAINS Formed when segments of Earth’s curst are bent and doubled over. Gentle slopping sides FAULT-BLOCK MOUNTAINS Formed when stress causes pieces of the crust in a fault zone to be thrust (pushed forcefully) upward. Mountains with sharper/jagged edges, and steep cliffs. Islands There is land under the ocean, (the ocean floor) and the movement of the plates under the water can give rise to ISLANDS (and other structures). An island is land that is completely surrounded by water. An island is land that is completely surrounded by water. Islands form as a result of oceanic plates pushing against each other (at a subduction zone). “How?!” you ask… A hotspot is a location when magma rises up through the Earth’s crust to form volcanoes… The oceanic plate moves (very slowly) over a “plume” which is releasing the magma. Because the plate is moving, as it cools it forms a chain of islands. Volcanoes that form over hotspots are known as shield volcanoes. Differences in Geological Areas: FLORIDA COLORADO Differences in Geological Areas: FLORIDA - Flat land COLORADO - Mountains Differences in Geological Areas: FLORIDA - Flat land - Younger land COLORADO - Mountains - Older land Differences in Geological Areas: FLORIDA - Flat land - Younger land - Hasn’t experienced as much impact from weather (erosion) COLORADO - Mountains - Older land - Has experienced lots of impact from weather (erosion and rebuilding) “The process of mountain building takes time— typically many millions of years.” Geologic structures are constantly forming and reforming, but usually so slow that you wouldn’t notice at all. “Geologic structures build up as a result of processes resulting from tectonic plate movement: volcanism, folding, and faulting.” What to do; Lesson 4 What to do; Lesson 4 What to do; Lesson 4 - Answer all questions and at the bottom check the box, and finally click “submit”. Lesson 5 Lesson 5 Volcanoes are usually found where two tectonic plates meet (plate boundaries). Remember some volcanoes can form at a hotspot (away from boundaries). Usually volcanoes build mountains. A volcano is any location where molten rock and other materials make their way to Earth’s crust and onto the surface. Ring of Fire – No, it’s not really a ring with fire around it; it’s the most seismically and volcanically active zone in the world. It surrounds the Pacific Ocean Be sure the read the “text-only” to understand this better! Types of Volcanoes Cylinder cone: Magma and ash shoot out and harden in the air, then pile up on the sides creating the cone. Stratovolcano: These are formed from alternating eruptions; creating a steep cone. Shield Volcano: Very wide slopes; usually form over a hot spot. Lava Dome: Really thick lava piles up as it exits the vent; usually formed by one eruption. Earthquakes The upper part of the Earth’s crust is pretty breakable (they call this brittle). When it is under “stress” from movements below it can break; this is an earthquake. Earthquakes Earthquakes happen along boundaries (usually transform boundaries). When the rock breaks energy is released, this is called seismic energy or waves. “A seismic wave is any ground movement that results from energy released during an earthquake. The point in the Earth’s crust where the rock ruptures is the focus. The point on Earth’s surface directly above the focus is the epicenter.“ Body waves: Surface waves Two types of body waves: P waves: S waves: Body waves: P-waves: Primary waves or compression waves Travel through the solid and liquid parts of Earth Fastest earthquake waves Always the first waves to appear on a seismogram Cause ground to move horizontally back and forth through compression. P-waves bounce off the liquid core. Body waves: S-waves: Secondary waves or shear waves Can travel through Earth’s solid portions only When they hit the liquid core, S-waves are no longer able to be detected. A shadow zone is created where earthquake waves are not detected S-waves are absorbed at the core. Cause ground to move back and forth in an S-shaped pattern Two types of surface waves: R waves: L waves: Surface waves: R-waves (Rayleigh waves) Cause lots of damage to the surface of the Earth, especially to buildings Have a rolling motion, like the waves of the ocean L-waves (Love waves) Cause lots of damage to the surface of the Earth, especially to buildings Have a side-to-side motion similar to the movement of a snake Modeling Geologic Events Scientists use models to help understand what will happen during a geologic event, such as an earthquake or volcano eruption. Creating a model allows them to attempt to see what type of damage could occur as a result of one of those events and how intense the event could be. 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