Editing Geology (section)

===Earth structure===
{{Main|Structure of the Earth}}
[[File:Jordens inre-numbers.svg|thumb|left|The [[Earth]]'s layered structure. (1) inner core; (2) outer core; (3) lower mantle; (4) upper mantle; (5) lithosphere; (6) crust (uppermost part of the lithosphere)]]
[[File:Earthquake wave paths.svg|thumb|upright=1.35|Earth layered structure. Typical wave paths from earthquakes like these gave early seismologists insights into the layered structure of the Earth.]]

Advances in [[seismology]], [[computer modeling]], and [[mineralogy]] and [[crystallography]] at high temperatures and pressures give insights into the internal composition and structure of the Earth.

Seismologists can use the arrival times of [[seismic wave]]s to image the interior of the Earth. Early advances in this field showed the existence of a liquid [[outer core]] (where [[S-wave|shear waves]] were not able to propagate) and a dense solid [[inner core]]. These advances led to the development of a layered model of the Earth, with a [[lithosphere]] (including crust) on top, the [[mantle (geology)|mantle]] below (separated within itself by [[seismic tomography|seismic discontinuities]] at 410 and 660 kilometers), and the outer core and inner core below that. More recently, seismologists have been able to create detailed images of wave speeds inside the earth in the same way a doctor images a body in a [[CT scan]]. These images have led to a much more detailed view of the interior of the Earth, and have replaced the simplified layered model with a much more dynamic  model.

Mineralogists have been able to use the pressure and temperature data from the seismic and modeling studies alongside knowledge of the elemental composition of the Earth to reproduce these conditions in experimental settings and measure changes within the crystal structure. These studies explain the chemical changes associated with the major seismic discontinuities in the mantle and show the crystallographic structures expected in the inner core of the Earth.
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