Volcanoes and their relation to plate tectonics
I chose to compare the relationship between plate boundaries, volcanoes and earthquakes. The layers I chose satisfied the fact that magma. Earthquakes, volcanoes, and tsunamis are all dangerous natural disasters, but they also have something else in common - tectonic plate. As the tectonic plates split apart magma (molten rock) wells up from below But a couple of years later in there was another eruption in Iceland, at a.
The outer portion of the planet, or lithosphere, is relatively rigid because it is relatively cold. The lithosphere varies in thickness but is typically a hundred or so kilometers thick. It includes the upper mantle and both the continental and oceanic crust.
These plates may move away from, move by, or collide with each other. This process forms ocean basins, shifts continents, and pushes up mountains. Tectonic plates break apart and diverge where the mantle beneath is upwelling. In such regions mid-ocean ridges develop, and new lithosphere and crust form to replace the material that is moving away. Where plates converge, usually where the mantle is downwelling, one plate is forced beneath another.
When this involves plates with embedded continental crust, mountain belts such as the Alps and Himalayas form.
If the collision involves plates with oceanic crust, subduction zones form where one plate descends into the mantle beneath the other plate. Above these subduction zone chains of volcanoes and island arcs like the Aleutians, develop. Below the Aleutian island arc, at depths of to kilometers, water is forced out of the subducted Pacific plate.
This water lowers the melting point of the overlying mantle, causing it to melt. The melting forms magma, which rises to feed the 55 currently active volcanoes that make up the island arc.
California's San Andreas fault system is an example.
So mantle convection not only accounts for ocean basins, continents, and mountains, it is also the ultimate reason for nearly all earthquakes and volcanoes. The San Andreas is probably the best-known transform fault boundary.
In fact, the connected mid-ocean ridge system is in essence a 80, km long volcano. Over the course of several million years, all of the water in the world's oceans cycles through the oceanic crust at mid-ocean ridges. This is how the hydrothermal circulation influences ocean composition. Eventually, arc volcanism can yield large stratovolcanoes, such as the elegant symmetrical cone of Mt.
Periods of growth, however, may be interrupted by explosions that leave behind a blasted-apart hulk like Mt. Helens Volcanic Explosions to Remember below.
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In some places, they even host stratovolcanoes such as Mt. Oceanic Hot-Spot Volcanoes The interior of an oceanic hot-spot volcano is complicated. Initially, eruption produces pillow basalts.
When the volcano emerges above sea level, it becomes a shield volcano. The margins of the island frequently undergo slumping, and the weight of the volcano pushes down the surface of the lithosphere. The Hawaiian islands exemplify this architecture.
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With time, the volcano grows up above the sea surface and becomes an island. Recent and ongoing activity beneath Yellowstone has yielded fascinating landforms, volcanic rock deposits, and geysers.
Eruptions at the Yellowstone hot spot differ from those in Hawaii in an important way: The eruption produced an immense caldera, up to 72 km across. When the debris settled, it blanketed an area of 2, square km with tuffs that, in the park, reached a thickness of m.
Mantle Convection and Plate Tectonics
Flood-Basalt Eruptions Flood basalt layers exposed on the wall of a canyon in Idaho. The aggregate volume of rock in such a plateau may be so great overkm3that geologists also refer to the region as a large igneous province LIP. The basalt here, which erupted around 15 million years ago, reaches a thickness of 3. Eventually, basalt covered an area ofkm. Iceland is one of the few places on Earth where mid-ocean ridge volcanism has built a mound of basalt that protrudes above the sea.
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The island formed where a hot spot lies beneath the Mid-Atlantic Ridge the presence of this hot spot probably due to an underlying mantle plume means that far more magma erupted here than beneath other places along the ridge. Because Iceland straddles a divergent plate boundary, it is being stretched apart, with faults forming as a consequence.
This rift is the trace of the Mid-Atlantic Ridge. Faulting cracks the crust and so provides a conduit to a magma chamber.
Not all volcanic activity on Iceland occurs sub-aerially. Some eruptions take place under glaciers and melt large amounts of ice.
Volcanic Explosions to Remember Explosions of volcanoes generate enduring images of destruction. Helens, a snow-crested stratovolcano in the Cascades of the north-western United States, had not erupted since However, geologic evidence suggested that the mountain had a violent past, punctuated by many explosive eruptions.
On March 20,an earth quake announced that the volcano was awakening once again.