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Core
 Crater—A crater lies in the uppermost part of the cone and is the top of the vent. Notice the lava at the bottom of this crater and the many layers of rock (the remains of former eruptions) showing in the sides. This provides evidence that a volcano builds up as a result of many eruptions.
Core
The central region of the Earth. It is about 6,000km in diameter and is surrounded by the mantle.
Crater
The funnel-shaped depression surrounding the top of the vent in a violently exploding type of volcano.
As the magma rushes out of the vent, it tends to rip away the top of the vent, widening it and forming a cone. The exact shape and size of the crater depend on the violence of the eruption. At the end of
the eruption the crater will have very steep sides. The vent will
be blocked by the remains of the lava from the eruption, giving the appearance of a crater floor.
Over time the rock in the walls of the crater is attacked by the forces of weather, and chunks of rock from the sides fall into the bottom of the crater.
New craters thus have steep sides and an irregular floor, while old
craters have less steep sides and a flat floor.
Most craters on the top, or summit, of volcanoes are really very small compared to the size of the volcano, being just a
few hundred meters across and a hundred meters or so deep.
Many volcanoes have craters. Kilauea is a mountain on Hawaii that erupts almost every year. The material that comes from the vent, in the form of a lava fountain, is runny basalt. There are never any explosions.
During an eruption a lava lake may build up in the crater. Sometimes a cone may form, made from the cooling rock of a lava fountain.
A much larger “crater” is created by the collapse of the top of the volcano during a violent eruption. It produces a caldera.
Crater lake
A lake found inside a crater, but more usually inside a caldera.
Creep
The slow movement of one part of the Earth’s crust past another. It happens along a deep fracture called a fault line. Parts of the Earth’s crust that are creeping past one another do not tend to have large earthquakes.
Crust
The outermost layer of the Earth. The Earth is made up of three main layers: The very thin crust of brittle rocks that cover the surface; the central molten core; and a thick layer in between called the mantle.
The mantle and core together make up nearly the entire distance to the center of the Earth. By contrast, the crust makes up less than 1% of the Earth’s volume
and has an average thickness of about 35km. The crust can be
as little as 5km thick under the oceans, but more than 100km thick under continents.
The uppermost 15km to 35km of the continental crust is especially
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