How hot is the core and mantle of the earth?

How do we know that the crust, the mantle, outer core and inner core makes up the Earth, when nobody has been down there?

• Answer:

  "The inner core and crust are solid; the outer core and mantle layers are plastic or semi-fluid. The various layers are separated by discontinuities which are evident in SEISMIC DATA; the best known of these is the Mohorovicic discontinuity between the crust and upper mantle." "The core is probably composed mostly of iron (or nickel/iron) though it is possible that some lighter elements may be present, too. Temperatures at the center of the core may be as high as 7500 K, hotter than the surface of the Sun. The lower mantle is probably mostly silicon, magnesium and oxygen with some iron, calcium and aluminum. The upper mantle is mostly olivene and pyroxene (iron/magnesium silicates), calcium and aluminum. We know most of this only from SEISMIC TECHNIQUES; samples from the upper mantle arrive at the surface as lava from VOLCANOES but the majority of the Earth is inaccessible. The crust is primarily quartz (silicon dioxide) and other silicates like feldspar." Source (contains other very interestin information): http://seds.lpl.arizona.edu/nineplanets/nineplanets/earth.html Other interessant information: http://mediatheek.thinkquest.nl/~ll125/en/struct.htm http://en.wikipedia.org/wiki/Structure_of_the_Earth http://www.seismo.unr.edu/ftp/pub/louie/class/100/interior.html Some articles on modern issues: Earth's Core Rotates Faster than Surface: http://www.livescience.com/forcesofnature/050825_earthcore.html Hole Drilled to Bottom of Earth's Crust, Breakthrough to Mantle Looms: http://www.livescience.com/technology/050407_earth_drill.html Finally, a Solid Look at Earth's Core: http://www.livescience.com/forcesofnature/050414_earth_core.html About a new exploring technique with neutrinos: "The heart of our planet is largely a mystery because scientists can't go there or see what's inside. Geologists have just one tool, seismology, with which to probe the inner Earth." "There are still lots of theories about what's really inside the Earth" "For the first time, researchers have detected tiny particles called geoneutrinos coming from deep within the Earth. The discovery is expected to shed light, almost literally, on the contents and processes of the planet's insides." http://www.livescience.com/forcesofnature/050727_earth_neutrinos.html