Chapter 1: An Introduction to Geology Flashcards
Geology
The science that examines Earth, its form
and composition, and the changes that it has undergone
and is undergoing.
Physical Geology
A major division of geology that
examines the materials of Earth and seeks to understand
the processes and forces acting beneath and
upon Earth’s surface.
Historical Geology
A major division of geology that
deals with the origin of Earth and its development
through time. Usually involves the study of fossils and
their sequence in rock beds.
Hypothesis
A tentative explanation that is then tested
to determine if it is valid.
Theory
A well-tested and widely accepted view that
explains certain observable facts.
Hydrosphere
The water portion of our planet; one
of the traditional subdivisions of Earth’s physical
environment.
Atmosphere
The gaseous portion of a planet, the
planet’s envelope of air. One of the traditional subdivisions
of Earth’s physical environment.
Biosphere
The totality of life-forms on Earth.
Geosphere
The solid Earth; one of Earth’s four basic
spheres.
System
A group of interacting or interdependent
parts that form a complex whole.
Nebular Theory
A model for the origin of the solar
system that supposes a rotating nebula of dust and
gases that contracted to form the Sun and planets.
Solar Nebula
The cloud of interstellar gas and/or dust
from which the bodies of our solar system formed.
Crust
The very thin, outermost layer of Earth.
Mantle
One of Earth’s compositional layers. The solid
rocky shell that extends from the base of the crust to a
depth of 2900 kilometers (1800 miles).
Lithosphere
The rigid outer layer of Earth, including
the crust and upper mantle.
Asthenosphere
subdivision of the mantle situated
below the lithosphere. This zone of weak material
exists below a depth of about 100 kilometers (60 miles)
and in some regions extends as deep as 700 kilometers
(430 miles). The rock within this zone is easily
deformed.
Lower Mantle (Mesosphere)
The part of the mantle that extends
from the core–mantle boundary to a depth of 660 kilometers
(410 miles).
Core
The innermost layer of Earth. It is thought to
be largely an iron–nickel alloy, with minor amounts of
oxygen, silicon, and sulfur.
Outer Core
A layer beneath the mantle about
2270 kilometers (1410 miles) thick, which has the
properties of a liquid.
Inner Core
The solid innermost layer of Earth, about 1216 kilometers (754 miles) in radius.
Rock Cycle
A model that illustrates the origin of
the three basic rock types and the interrelatedness of
Earth materials and processes.
Igneous Rocks
Rock formed from the crystallization of
magma.
Sediment
Unconsolidated particles created by the
weathering and erosion of rock by chemical precipitation
from solution in water, or from the secretions of
organisms, and transported by water, wind, or
glaciers.
Sedimentary Rock
Rock formed from the weathered
products of preexisting rocks that have been transported,
deposited, and lithified.
Metamorphic Rock
Rock formed by the alteration
of preexisting rock deep within Earth (but still in the
solid state) by heat, pressure, and/or chemically active
fluids.
Craton
The part of the continental crust that has
attained stability; that is, it has not been affected by
significant tectonic activity during the Phanerozoic
eon. It consists of the shield and the stable platform.
Shield
A large, relatively flat expanse of ancient
igneous and metamorphic rocks within the craton.
Stable Platform
That part of a carton that is mantled by
relatively undeformed sedimentary rocks and underlain
by a basement complex of igneous and metamorphic
rocks.
Continental Margin
The portion of the seafloor that
is adjacent to the continents. It may include the continental
shelf, continental slope, and continental rise.
Continental Shelf
The gently sloping submerged portion
of the continental margin, extending from the
shoreline to the continental slope.
Continental Slope
The steep gradient that leads to
the deep-ocean floor and marks the seaward edge of
the continental shelf.
Continental Rise
The gently sloping surface at the
base of the continental slope
Deep-Ocean Basin
The portion of seafloor that lies
between the continental margin and the oceanic ridge
system. This region comprises almost 30 percent of
Earth’s surface.
Abyssal Plain
A very level area of the deep-ocean
floor, usually lying at the foot of the continental rise.
Deep-Ocean Trench
A narrow, elongated depression
of the seafloor.
Seamount
An isolated volcanic peak that rises at least 1000 meters (3300 feet) above the deep-ocean floor.
Oceanic Ridge (Mid-Ocean Ridge)
A continuous mountainous ridge
on the floor of all the major ocean basins and varying
in width from 500 to 5000 kilometers (300 to
3000 miles). The rifts at the crests of these ridges
represent divergent plate boundaries.
Catastrophism
The concept that Earth was shaped by
catastrophic events of a short-term nature.
Uniformitarianism
The concept that the processes
that have shaped Earth in the geologic past are essentially
the same as those operating today.
