文档介绍：Earth’s Internal Structure
When a meteorite impacts a or moon, its energy of motion (called ic energy) is transformed into heat energy.
As Earth grew larger and larger from continual impacts, its temperature increased.
Radioactive decay of materials like uranium, thorium and potassium also added heat.
Because Earth became partly fluid, less-dense molten materials (silicon, aluminum, sodium, and potassium) were freed to migrate toward the surface.
Denser melted materials, such as molten iron, sank toward the center of the .
Earth’s Internal Structure
The Earth’s Interior
Earth has three main parts:
At the center is the densest part, the core (metallic iron, nickel).
Surrounding the core is the mantle.
Surrounding the mantle lies the thinnest and outermost layer, the crust.
Inside Earth
The Earth’s Crust
The crust is not uniform.
The oceanic crust on average is about 8 km thick.
The continental crust on average is about 45 km thick.
Investigating the Earth’s Interior
How do we know anything about position of the core and the mantle?
By measuring the time required for earthquake waves to travel through Earth by different paths, we can determine position of the materials through which they move.
Iron meteorites are believed to be fragments from the core of a small terrestrial that was shattered by a gigantic impact.
The Layers of the Earth’s Interior (1)
The inner core
Pressures are so great that iron is solid, despite its high temperature.
The outer core
Iron is molten and exists as a liquid.
The Mesosphere
The mantle between the bottom of the asthenosphere to the core-mantle boundary.
The temperature at the core-mantle boundary is about 50000C.
The Layer of the Earth’s Interior (2)
The Asthenosphere:
The region of the mantle where rocks e ductile, have little strength, and are easily deformed. It lies at a depth of 100 to 350 km below the surface.
The Lithosphere:
The outer 100 km of the solid Earth, where rocks are harder and more rigid than