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16 Topic Pages Found in Geology and starting with the letter P
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Open paleontology

( pā´´lēəntŏl'əjē ) [Gr.,= study of early beings], science of the life of past geologic periods based on fossil remains. Knowledge of the existence of

Open Pearls

Originally, and until the last century, one could only dive for pearls, and few of the shells collected during dives contained any. They were thus

Open Pegmatite

PEGMATITE IS THE NAME given to very coarse-grained, igneous rocks. Most have the same major constituents – quartz and feldspar – as granites or

Open Peneplains

A planation surface of gentle relief formed through long-term denudation . The term is associated in particular with the davisian cycle of erosion

Open Peridotite

ONE OF THE MOST ECONOMICALLY important rocks, peridotite is the ultimate source of all chromium ore, and its variety kimberlite is the source of

Open Peridots

Peridot is the gem-quality variety of the mineral OLIVINE . A rock- forming mineral, olivine occurs in silica-poor igneous rocks, such as basalts,

Permian period

( pûr'mēən ) [from Perm, Russia], sixth and last period of the Paleozoic era (see Geologic Timescale , table) from 250 to 290 million years ago. The

Open Petroleum

PETROLEUM, OR CRUDE oil, is a nonrenewable natural resource that has had a tremendous beneficial influence on human society. With a name derived from

Open Phonolite

PHONOLITE IS A TYPE OF TRACHYTE (see here ) that contains nepheline or leucite rather than quartz. They are commonly fine grained and compact, and

Open Pingos

Pingos are ice-cored hills ( Figure P63 ), typically conical in shape, covered by soil and vegetation with a core of massive ice produced primarily by