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Plate Tectonics

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Dynamic Earth . Plates & Boundaries. Volcanic Hazards of Yellowstone National Park. Yellowstone National Park is part of the largest active volcanic systems. Many of the geologic features at Yellowstone are connected with the fact that the park lies on a 'hot spot’. The volcanic activity of Yellowstone's past was from caldera eruptions, which are giant explosions with violence, noise and enormous destruction.

This diagram shows the 'track' of the Yellowstone 'hot spot' Source: PowerPoint Presentation, Lori Snyder, Department of Geology, University of Wisconsin- Eau Claire Volcanic History and Recent Seismic Activity in the Yellowstone region The diagram above shows how active this region is and where the previous caldera volcanoes were located. The first eruption, the Huckleberry Ridge eruption is said to have erupted 2.1 million years ago and the debris from that volcano reached as far as the Iowa and central Texas. At Golden Gate, above, deposits from the Huckleberry Ridge eruption can be observed.

Lava Creek Tuff is exposed on the scarp. Hawaiian Volcanoes. Plate Tectonics | Pacific Northwest Seismic Network. Plate tectonics describes the motions of the 15 to 20 large rigid and brittle tectonic plates into which the Earth's outermost layer (called the "lithosphere") is broken. It does a good job at explaining the distribution of most of Earth's earthquakes, mountains and other geological features, and a particularly good job at explaining features on the ocean floor. However, it is challenged to explain the details of the older rocks on the continents, and the occurrence of deformation an earthquakes off of plate boundaries. Beyond merely describing current plate motions, Plate Tectonics provides an overarching framework that connects many elements of Earth science. Plate tectonics is a relatively young scientific theory that needed the advancement of observational and computing technology in the 1950s and 1960s to become fully elaborated.

This animation shows, in a very exaggerated way, the sorts of movements Plate Tectonics implies. Aleutian Trench. Hawaiian hotspot [This Dynamic Earth, USGS] Over the past 70 million years, the combined processes of magma formation, volcano eruption and growth, and continued movement of the Pacific Plate over the stationary Hawaiian "hot-spot" have left a long trail of volcanoes across the Pacific Ocean floor. The Hawaiian Ridge-Emperor Seamounts chain extends some 6,000 km from the "Big Island" of Hawaii to the Aleutian Trench off Alaska. The Hawaiian Islands themselves are a very small part of the chain and are the youngest islands in the immense, mostly submarine mountain chain composed of more than 80 volcanoes.

The length of the Hawaiian Ridge segment alone, from the Big Island northwest to Midway Island, is about equal to the distance from Washington, D.C. to Denver, Colorado (2,600 km). The amount of lava erupted to form the Hawaiian-Emperor chain is calculated to be at least 750,000 cubic kilometers-more than enough to blanket the entire State of California with a layer of lava roughly 1.5 km thick.

"Hotspots" Mountain Maker, Earth Shaker | Science | Classroom Resources | PBS Learning Media. Plate Tectonics: An Introduction | Science | Classroom Resources | PBS Learning Media. Divergent Plate Boundaries - Divergent Boundary - Earth Floor: Plate Tectonics. Divergent Boundaries Places where plates are coming apart are called divergent boundaries. As shown in the drawing above, when Earth's brittle surface layer (the lithosphere) is pulled apart, it typically breaks along parallel faults that tilt slightly outward from each other.

As the plates separate along the boundary, the block between the faults cracks and drops down into the soft, plastic interior (the asthenosphere). The sinking of the block forms a central valley called a rift. Magma (liquid rock) seeps upward to fill the cracks. In this way, new crust is formed along the boundary. Earthquakes occur along the faults, and volcanoes form where the magma reaches the surface. Where a divergent boundary crosses the land, the rift valleys which form are typically 30 to 50 kilometers wide. Plate separation is a slow process. Back | Next. Discovering Plate Boundaries Home. Multimedia Gallery: (Video)--Caldera Demonstration Model. Dina: Hi. I’m Dr. Dina. I work with the U.S. Geological Survey in Menlo Park, California with the Volcano Hazards Program. Today, we’re going to talk about calderas. When most people think about volcanoes, they think of a triangle shape and that’s what many volcanoes look like, but there are other shapes too, and one of those is called a caldera.

Underneath the surface of the earth, we’re going to inject some magma. As you can see, the flower is being moved out of the way as we inflate the balloon or add magma to the system. To do that, I’m going to let the air out of the balloon and then we’re going to watch to see what happens. So as the air comes out of the balloon, we want to imagine the magma escaping from the magma chamber. For more information, please see the following web sites.

USGS Volcano Hazards Program: Yellowstone: Long Valley Caldera: Episode 1: Yellowstone's Restless Giant - Yellowstone National Park. Glossary Earthquake – The abrupt shaking of the ground caused by a shift of rock along a fracture in the Earth. Geyser – Hot springs that periodically erupt, shooting scalding water and steam into the air. Though hot springs can be common, the special requirements needed for a geyser to erupt make them rare. In addition to hot water, a unique conduit system or natural “plumbing” system is needed for pressure to build and yet withstand the force of eruptions. A narrow constriction above a larger reservoir chamber allows water to become superheated above the boiling point without boiling. In Yellowstone, the cracks and fissures underground that make up the plumbing system of geysers are lined with silica that the hot water has dissolved out of rhyolite rock and redeposited along the inner walls of fissures.

This glass-like lining creates a watertight seal that allows pressure to build within the conduit and produce geyser eruptions. Mount St. Tracking the Hot Spot - Yellowstone National Park. High School Earth Science/Theory of Plate Tectonics. Wegener's continental drift hypothesis had a great deal of evidence in its favor but it was largely abandoned because his theory on how the continents moved was disproved. In the meantime, scientists developed explanations to explain the locations of fossils on widely different continents (land bridges) and the similarity of rock sequences across oceans (geosynclines), which were becoming more and more cumbersome.

When seafloor spreading came along, scientists recognized that the mechanism to explain drifting continents had been found. Like the scientists did before us, we are now ready to merge the ideas of continental drift and seafloor spreading into a new all-encompassing idea: the theory of plate tectonics. Lesson Objectives Earth's Tectonic Plates Now you know that seafloor and continents move around on Earth's surface. But what is it that is actually moving? Earthquakes are not spread evenly around the planet, but are found mostly in certain regions. How Plates Move Plate Boundaries. Earthquakes suggest new tectonic plate is forming. Two magnitude-8 earthquakes took place within two hours in unstable plate region Keith Koper (CBS News) A new study suggests that two recent earthquakes may indicate a literal seismic shift in our understanding of tectonic plate movements.

Massive earthquakes under the Indian Ocean that took place last spring are the largest of their kind ever recorded. The 8.7 magnitude quake, followed by a 8.2 magnitude aftershock, could signal the formation of a new plate boundary under the Earth. While not the largest earthquakes ever recorded, the two quakes are notable for their unusual location. The majority of earthquakes are known as thrust faults: massive sheets of rock sliding over or under another block along a fault line. The two earthquakes recorded in April were strike-slip faults, where one block of rock slides alongside another. Additionally, the two earthquakes took place within a plate, rather than on its edge.

. © 2012 CBS Interactive Inc. Tectonic Plates. The edges of these plates, where they move against each other, are sites of intense geologic activity, such as earthquakes, volcanoes, and mountain building. Plate tectonics is a relatively new theory and it wasn't until the 1960's that Geologists, with the help of ocean surveys, began to understand what goes on beneath our feet. Where is the Evidence for Plate Tectonics? It is hard to imagine that these great big solid slabs of rock could wander around the globe. Scientists needed a clue as to how the continents drifted. The discovery of the chain of mountains that lie under the oceans was the clue that they were waiting for.

Click here for the Scotland story Picture the following in your mind: You have a nine piece jigsaw (now there's a challenge). What do you think will happen to the puzzle? Now let's think back to our plates being created at the mid-ocean ridges, it seems to be a good idea but if this is the only type of plate movement then the world would get bigger and bigger. Granite - Yosemite National Park. A large amalgamation of plutons is called a batholith. Yosemite is situated within the 70-mile-wide, 300-mile-long Sierra Nevada Batholith. Most of the granite in the Sierra Nevada Batholith was emplaced between 120 and 85 million years ago during the Jurassic and Cretaceous periods.

This means that 618 cubic feet of granite were emplaced each year (roughly the equivalent of 7 great pyramids of Giza.) This is one of the most rapid periods of continental crust assembly known. In fact, it has been speculated that this voluminous volcanism may have contributed to the mass extinction during the middle of the Cretaceous period during which most large marine dinosaurs (ichthyosaurs and plesiosaurs) perished. Hot Research Few places on earth display the internal complexity of a batholith better than El Capitan. High School Earth Science/Theory of Plate Tectonics. Geology in the Parks. In a contest between a dense oceanic plate and a less dense, buoyant continental plate, guess which one will sink?

The dense, leading edge of the oceanic plate actually pulls the rest of the plate into the flowing asthenosphere and a subduction zone is born! Where the two plates intersect, a deep trench forms. Geologists aren't sure how deep the oceanic plate sinks before it completely melts, but we do know that it remains solid far beyond depths of 100 km beneath the Earth's surface. When the subducting oceanic plate sinks deeper than 100 kilometers, huge temperature and pressure increases make the plate ‘sweat'. This hot, freshly melted liquid rock (magma) makes its way toward the surface. Some molten rock may break through the Earth's surface, instantly releasing the huge pressure built up in the gas-rich magma chambers below. An example of this kind of convergence produces the spectacular volcanic landscape of the Northwest. Why is the seafloor so recent and the continental crust so old? | Geology | Earth Observatory of Singapore. How Tall Can Mountains Be? Continental crust. The thickness of the Earth's crust (km). Importance[edit] Because the surface of continental crust mainly lies above sea level, its existence allowed land life to evolve from marine life. Its existence also provides broad expanses of shallow water known as epeiric seas and continental shelves where complex metazoan life could become established during early Paleozoic time, in what is now called the Cambrian explosion.[3] Origin[edit] Forces at work[edit] In contrast to the persistence of continental crust, the size, shape, and number of continents are constantly changing through geologic time.

Different tracts rift apart, collide and recoalesce as part of a grand supercontinent cycle.[5] There are currently about 7 billion cubic kilometers of continental crust, but this quantity varies because of the nature of the forces involved. The height of mountain ranges is usually related to the thickness of crust. See also[edit] Notes[edit] References[edit] Armstrong, R.L. (1991). External links[edit] Plate Tectonics : Earthview. The Geological Society. The Himalayan mountain range and Tibetan plateau have formed as a result of the collision between the Indian Plate and Eurasian Plate which began 50 million years ago and continues today. Northward migration of India 225 million years ago (Ma) India was a large island situated off the Australian coast and separated from Asia by the Tethys Ocean. The supercontinent Pangea began to break up 200 Ma and India started a northward drift towards Asia. 80 Ma India was 6,400 km south of the Asian continent but moving towards it at a rate of between 9 and 16 cm per year.

At this time Tethys Ocean floor would have been subducting northwards beneath Asia and the plate margin would have been a Convergent oceanic-continental one just like the Andes today. Between 40 and 20 Ma the rate of northward drift slowed as the two continental plates collided and the former Tethys Ocean closed. Neither continental plate could be subducted due to their low density/buoyancy. Earth Floor: Plate Tectonics.

The theory of plate tectonics has done for geology what Charles Darwin's theory of evolution did for biology. It provides geology with a comprehensive theory that explains "how the Earth works. " The theory was formulated in the 1960s and 1970s as new information was obtained about the nature of the ocean floor, Earth's ancient magnetism, the distribution of volcanoes and earthquakes, the flow of heat from Earth's interior, and the worldwide distribution of plant and animal fossils. The theory states that Earth's outermost layer, the lithosphere, is broken into 7 large, rigid pieces called plates: the African, North American, South American, Eurasian, Australian, Antarctic, and Pacific plates.

Several minor plates also exist, including the Arabian, Nazca, and Philippines plates. The plates are all moving in different directions and at different speeds (from 2 cm to 10 cm per year--about the speed at which your fingernails grow) in relationship to each other. Next. Plate Tectonics in a Nutshell. The theory of plate tectonics is a relatively new scientific concept. While its forerunner—the theory of continental drift—had its inception as early as the late 16th century, plate tectonics only emerged and matured as a widely accepted theory since the 1960s (see This Dynamic Earth booklet). In a nutshell, this theory states that the Earth’s outermost layer is fragmented into a dozen or more large and small solid slabs, called lithospheric plates or tectonic plates, that are moving relative to one another as they ride atop hotter, more mobile mantle material (called the asthenosphere).

The average rates of motion of these restless plates—in the past as well as the present—range from less than 1 to more than 15 centimeters per year. With some notable exceptions, nearly all the world’s earthquake and volcanic activity occur along or near boundaries between plates. Using the Diagram to Discuss How Plate Tectonics Works There are two basic types of LITHOSPHERE: continental and oceanic. New Ocean - The New Southern Ocean. Index of /eoc/teachers/t_tectonics. Plate Tectonics. Chapter -12 HW. Flipbook.pdf. Tri fold note books (evidence, boundaries, causes) - Mrs. Lafrate's Class. CHAPTER 10 PLATE TECTONICS.pdf. Plate Tectonic Animation - Earthguide Online Classroom - Plate Tectonics Animations.