Principle of superposition relative dating
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 waves in reverse to image the interior of the Earth.Geology describes the structure of the Earth beneath its surface, and the processes that have shaped that structure.It also provides tools to determine the relative and absolute ages of rocks found in a given location, and also to describe the histories of those rocks.) is an earth science concerned with the solid Earth, the rocks of which it is composed, and the processes by which they change over time.Geology can also refer to the study of the solid features of any terrestrial planet or natural satellite, (such as Mars or the Moon).Geology, a major academic discipline, also plays a role in geotechnical engineering.
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.
The blue blob in the cutaway section is the seismically imaged Farallon Plate, which is subducting beneath North America.
The remnants of this plate on the surface of the Earth are the Juan de Fuca Plate and Explorer Plate, both in the northwestern United States and southwestern Canada, and the Cocos Plate on the west coast of Mexico.
There is an intimate coupling between the movement of the plates on the surface and the convection of the mantle (that is, the heat transfer caused by bulk movement of molecules within fluids).
Thus, oceanic plates and the adjoining mantle convection currents always move in the same direction — because the oceanic lithosphere is actually the rigid upper thermal boundary layer of the convecting mantle.
There are three major types of rock: igneous, sedimentary, and metamorphic.