Ch. 2, section 3 Internal Forces

Internal ForcesShaping the Earth

Plate Tectonics ,[object Object]

The tectonic plates are the sections of the Earth’s lithosphere (the Earth’s crust and upper mantle) that float around on the molten activities of the mantle,[object Object]

Convergent boundary: the plates collide (2 types) Subduction: the plates collide and one plate is forced under the other. Often, the plate that is forced under will melt when it gets deep and hot enough and the resulting magma forces its way back to the surface as a volcano.

Collision: The plates collide and buckle and fold. Mountains may result. Take India, for example. Remember this? That’s India. Note that it’s on its own tectonic plate Millions of years ago, the thing rampaged north and crashed into Asia. It created the Himalaya Mountains, including Mt. Everest. Even today, the mountains are still growing by a few millimeters per year. They’ve also found ancient ocean fossils in these, the highest points on Earth.

Subduction happens when the density of one plate is less than the other (usually the oceanic crust subducting under a continental crust),[object Object],[object Object]

Normally (hopefully), the plates slide past each other steadily and gradually and we don’t notice it.

Sometimes, though, the crust at the fault sticks, but the plates keep moving. This builds up tremendous pressure on the stuck crusts until they finally unstick and they suddenly move a lot at once. This is when the earthquake happens.

All that kinetic energy is released at once instead of gradually.,[object Object],[object Object],[object Object]

The earthquake’s focus is the point underground at which the quake originates. ,[object Object],[object Object]

The 2004 earthquake in the Indian Ocean that caused the tsunami measured 9.0 and released energy equivalent to 30 gigatons (30 BILLION tons) of TNT.,[object Object]

An earthquake occurs on the ocean floor or along the coast. The energy travels as waves through the water and across the ocean until it gets to a coast. The shallow region causes the wave to rush over land and flood the place.,[object Object]

This shows the progression of the 2004 tsunami

The Empire State Building is 1,250 feet tall.

That’s a big wave.,[object Object]

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Sometimes it’s a gradual flow. Other times, it erupts in a violent explosion, sometimes releasing more energy than nuclear weapons.

Usually found along tectonic plate boundaries. Most are along the “Ring of Fire” seen on p.37. It follows the plate boundaries.,[object Object]

Ch. 2, section 3 Internal Forces

Ch. 2, section 3 Internal Forces

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Ch. 2, section 3 Internal Forces