Rocky road.Geologists A geologist is a contributor to the science of geology. Geologists are also known as earth scientists or geoscientists. The following is a list of famous or notable geologists. have just added a new chapter to Earth's lengthy time line, called the geologic time scale The geological time scale is used by geologists and other scientists to describe the timing and relationships between events that have occurred during the history of Earth. . This scale divides Earth's history into eras (long units of geologic time geologic time Interval of time occupied by the Earth's geologic history, extending from c. 3.9 billion years ago (corresponding to the age of the oldest known rocks) to the present day. It is, in effect, the part of the Earth's history that is recorded in rock strata. ) and periods (subdivisions of eras). These divisions are based on major changes in the types of life forms that inhabited in·hab·it·ed adj. Having inhabitants; lived in: a sparsely inhabited plain. Adj. 1. inhabited - having inhabitants; lived in; "the inhabited regions of the earth" the planet, explains Andrew Knoll, a geologist at Harvard University Harvard University, mainly at Cambridge, Mass., including Harvard College, the oldest American college. Harvard College Harvard College, originally for men, was founded in 1636 with a grant from the General Court of the Massachusetts Bay Colony. . Geologists track the changes using fossils (traces of ancient organisms Organisms See also animals; bacteria; biology; plants; zoology. anabolism Biology, Physiology. the synthesis in living organisms of more complex substances from simpler ones. Cf. catabolism. — anabolic, adj. found in rocks) in different rock layers. The scale's newcomer--dubbed the Ediacaran (eedee-AH-kah-ren) Period--represents the time when scientists believe the first soft-bodied animals appeared on Earth.
GEOLOGIC TIME SCALE
MILLIONS OF
YEARS AGO ERA PERIOD
Cenozoic Quaternary UP TO
Tertiary DATE: You
live during
this period.
65 Mesozoic Createous
Jurassic
Triassic
248 Paleozoic Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
543 Late Ediacaran NEWCOMER:
Proterozoic Cryogenian The new
period
stretches
from 600
to 544
million
years ago.
*
4,600 Earth was formed
SOURCE: THE GEOLOGICAL SOCIETY OF AMERICA, 1999.
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