The Earth's Inside
Thanks to earthquakes, the seimic waves they give off and the instruments used to gather data abouth such events, we now know the chemical composition , temperature, density and depth of the layer's of the Earth's inside.
The earth is divided in to four layers:CRUST, MANTLE, OUTER CORE and INNER CORE.
Echo-sounding techniques are used to explore the Earth's crust. Images, similar to sonograms, are produced. A sonogram in the crust is called a seismic reflection. Seiscmic waves from "small explosions or thumper trucks" return echoes from rock layers. Seismographs pick up these echoes.
Some facts about the CRUST:
***two types: oceanic and continental
***calcium (Ca) and sodium (na) aluminium-silicates
***rocky and brittle
***fractures during earthquakes
***.473% of Earth's mass
***depth of 0-50 kilometers (0-31 miles)
Some facts about the MANTLE:
***iron (Fe), magnesium (Mg), aluminium (Al), silicon (Si) and oxygen (O) silicate compunds
***solid but can slowly deform in a plastic manner
***67.3% of Earth's mass
***depth of 10-2890 kilometers(6-1806 miles)
***convection in this region drives plate tectonics
Convection in the MANTLE:
Data about P waves and S waves traveling through the mantle has been used to map out convection in the mantle. Waves tell researchers whether the mantle is more or less dense than average, hotter or cooler than average and whether it is rising and falling.
The Earth releases internal heat by convecting. Hot mantle rises to the surface and spreads laterally, transporting oceanic and continental plates. Speed of this motion is a few centimeters per year. The new lithosphere, created at the ocean spreading centers, cools and evetuallu sinks back into the mantle. The subducted crust releases water to form island chains above.
Below are two images of mantle convection. Both were created at the Harvard Univerisity Seismology Lab.
||Red blobs are warmer plumes of less dense material, rising mostly into the ocean-ridge spreading centers. Most of the heat from the Earth's inside emerges at the fast-spreading East Pacific Rise. A huge plume, directly from the Earth's core seems to be spreading there.
||Blue blobs show where colder, denser material is sinking into the mantle.
Some facts about the OUTER CORE:
***iron and 10% sulphur (S) and/or oxygen
***30.8% of Earth's mass
***depth of 2890-5150 kilomters (1806-3219 miles)
***convection motion within this region, along with the rotation of the Earth creates an effect that maintains the Earth's magnetic field
Convection in the CORE:
Click on image to see enlarged version.
The yellow is the region where fluid flow from the Earth's outer core is the greatest. Red mush is the inner core boundary. Large flows exist on an imaginary tangent cylinder due to the effects of the Earth's rotations, fluid viscosity and the presence of the solid inner core within the spherical shell of the outer fluid core.
Some facts about the INNER CORE:
***solid and unattached to the mantle
***suspended in molten outer core
***1.7% of the Earth's mass
***depth of 5150-6370 kilometers (3219-3981 miles)
In the years since the practice of seismic tomography was first introduced researchers have gathered enough data to provide the world with detailed accurate maps of the layers of the Earth's inside. More recently, scientists have begun to focus more attention on the boundaries between layers, rather that the layers themselves. Many believe that the future of seismic tomography, geophysics and earthquake prediction lies in understanding these boundaries, chemical processes that occur in their vecinity and how such events affect the Earth's surface.
Plate Tectonics and Earthquakes
Seismographs and Seismograms