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Greek geo- is earth and -logy
is word or discourse. Geology: science of the
earth's history, composition, and structure. Geologists have helped
establish the age of the Earth at about 4.5 billion years, and that
tectonic plates move over a viscous mantle to form the earth's
crust. Geologists help locate and manage the earth's natural
resources, such as oil.
Rock is a substance composed of minerals
and classified according to mineral composition. Rocks are generally
classified by the processes that formed them, and are thus separated
into igneous, sedimentary, and metamorphic rocks. Igneous rocks are
formed from molten magma, sedimentary rocks by deposition and
compression of particulate matter, and metamorphic rocks by either
of the first two categories after being changed by the effects of
temperature and pressure. In cases where organic material leaves
behind an imprint of itself in rock, the result is known as a
fossil.
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