High School Earth Science/Inside Earth  From Wikibooks, open
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navigation, search  Plate tectonics is the unifying theory of
geology. This important theory explains why Earth's geography
has changed through time and continues to change today. It
explains why some places are prone to earthquakes and some are
not; why some regions have deadly volcanic eruptions, some have
mild ones, and some have none at all; and why mountain ranges
are located where they are. Plate tectonic motions affect
Earth's rock cycle, climate, and the evolution of life. Plate
tectonic theory was developed through the efforts of many
scientists during the twentieth century.  Before you can learn
about plate tectonics, you need to know something about the
layers that are found inside Earth. From outside to inside, the
planet is divided into crust, mantle, and core. Often geologists
talk about the lithosphere, which is the crust and the uppermost
mantle. The lithosphere is brittle–