Earth's Layers
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Most of Earth's layers are made up of solid or partly melted rock. The innermost layers are mostly a mixture of metals. Earth's layers vary in thickness. The crust, the uppermost layer, is much thinner than the other layers. The crust is nearly all solid rock. Under the continents, the crust is mostly granite and other light rocks. Below the oceans, the crust is mostly made of basalt--a dark dense rock. The crust is by far the thinnest of Earth's layers. Under the continents the average thickness of the crust is about 24 miles, but it may be as much as 42 miles in mountainous regions . The crust is even thinner under the oceans. The ocean-floor crust has a thickness of approximately 4 miles.
The layer just below Earth's crust is the mantle. The mantle is about 1,800 miles thick and makes up more than two-thirds of the Earth's mass. At the boundary where the upper mantle meets the crust, the mantle rock is solid. This solid upper mantle and crust combine to form a rigid shell called the lithosphere.
Below the lithosphere, much of the rock material in the mantle is partly melted. This material can flow very slowly, like plastic that has been heated almost to its melting point. The solid lithosphere can be thought of as "floating" on this thick lower mantle. Seismologists who are scientists who listen to the vibrations of earthquakes discovered the lithosphere through their studies.
The innermost of Earth's layers is the core, which extends to the center of the Earth. The core is divided into two regions or layers--the outer core and the inner core. The outer core is about 1,400 miles thick, and is the only layer that is in a liquid state. It is made up mostly of molten iron and nickel, with some sulfur and oxygen also present. On the other hand the inner core is about 720 miles thick, and is even hotter than the outer core. It is more than likely that it is made of iron and nickle as well. However, the extremely high pressure so deep inside Earth keeps these metals in the inner core from melting.
The layer just below Earth's crust is the mantle. The mantle is about 1,800 miles thick and makes up more than two-thirds of the Earth's mass. At the boundary where the upper mantle meets the crust, the mantle rock is solid. This solid upper mantle and crust combine to form a rigid shell called the lithosphere.
Below the lithosphere, much of the rock material in the mantle is partly melted. This material can flow very slowly, like plastic that has been heated almost to its melting point. The solid lithosphere can be thought of as "floating" on this thick lower mantle. Seismologists who are scientists who listen to the vibrations of earthquakes discovered the lithosphere through their studies.
The innermost of Earth's layers is the core, which extends to the center of the Earth. The core is divided into two regions or layers--the outer core and the inner core. The outer core is about 1,400 miles thick, and is the only layer that is in a liquid state. It is made up mostly of molten iron and nickel, with some sulfur and oxygen also present. On the other hand the inner core is about 720 miles thick, and is even hotter than the outer core. It is more than likely that it is made of iron and nickle as well. However, the extremely high pressure so deep inside Earth keeps these metals in the inner core from melting.