Chapter 1: An Introduction to Geology

Question 1

Geology

Answer 1

The science that examines Earth, its form
and composition, and the changes that it has undergone
and is undergoing.

Question 2

Physical Geology

Answer 2

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.

Question 3

Historical Geology

Answer 3

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.

Question 4

Hypothesis

Answer 4

A tentative explanation that is then tested

to determine if it is valid.

Question 5

Theory

Answer 5

A well-tested and widely accepted view that

explains certain observable facts.

Question 6

Hydrosphere

Answer 6

The water portion of our planet; one
of the traditional subdivisions of Earth’s physical
environment.

Question 7

Atmosphere

Answer 7

The gaseous portion of a planet, the
planet’s envelope of air. One of the traditional subdivisions
of Earth’s physical environment.

Question 8

Biosphere

Answer 8

The totality of life-forms on Earth.

Question 9

Geosphere

Answer 9

The solid Earth; one of Earth’s four basic

spheres.

Question 10

System

Answer 10

A group of interacting or interdependent

parts that form a complex whole.

Question 11

Nebular Theory

Answer 11

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.

Question 12

Solar Nebula

Answer 12

The cloud of interstellar gas and/or dust

from which the bodies of our solar system formed.

Question 13

Crust

Answer 13

The very thin, outermost layer of Earth.

Question 14

Mantle

Answer 14

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).

Question 15

Lithosphere

Answer 15

The rigid outer layer of Earth, including

the crust and upper mantle.

Question 16

Asthenosphere

Answer 16

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.

Question 17

Lower Mantle (Mesosphere)

Answer 17

The part of the mantle that extends
from the core–mantle boundary to a depth of 660 kilometers
(410 miles).

Question 18

Core

Answer 18

The innermost layer of Earth. It is thought to
be largely an iron–nickel alloy, with minor amounts of
oxygen, silicon, and sulfur.

Question 19

Outer Core

Answer 19

A layer beneath the mantle about
2270 kilometers (1410 miles) thick, which has the
properties of a liquid.

Question 20

Inner Core

Answer 20

The solid innermost layer of Earth, about
1216 kilometers (754 miles) in radius.

Question 21

Rock Cycle

Answer 21

A model that illustrates the origin of
the three basic rock types and the interrelatedness of
Earth materials and processes.

Question 22

Igneous Rocks

Answer 22

Rock formed from the crystallization of

magma.

Question 23

Sediment

Answer 23

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.

Question 24

Sedimentary Rock

Answer 24

Rock formed from the weathered
products of preexisting rocks that have been transported,
deposited, and lithified.

Question 25

Metamorphic Rock

Answer 25

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.

Question 26

Craton

Answer 26

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.

Question 27

Shield

Answer 27

A large, relatively flat expanse of ancient

igneous and metamorphic rocks within the craton.

Question 28

Stable Platform

Answer 28

That part of a carton that is mantled by
relatively undeformed sedimentary rocks and underlain
by a basement complex of igneous and metamorphic
rocks.

Question 29

Continental Margin

Answer 29

The portion of the seafloor that
is adjacent to the continents. It may include the continental
shelf, continental slope, and continental rise.

Question 30

Continental Shelf

Answer 30

The gently sloping submerged portion
of the continental margin, extending from the
shoreline to the continental slope.

Question 31

Continental Slope

Answer 31

The steep gradient that leads to
the deep-ocean floor and marks the seaward edge of
the continental shelf.

Question 32

Continental Rise

Answer 32

The gently sloping surface at the

base of the continental slope

Question 33

Deep-Ocean Basin

Answer 33

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.

Question 34

Abyssal Plain

Answer 34

A very level area of the deep-ocean

floor, usually lying at the foot of the continental rise.

Question 35

Deep-Ocean Trench

Answer 35

A narrow, elongated depression

of the seafloor.

Question 36

Seamount

Answer 36

An isolated volcanic peak that rises at least
1000 meters (3300 feet) above the deep-ocean floor.

Question 37

Oceanic Ridge (Mid-Ocean Ridge)

Answer 37

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.

Question 38

Catastrophism

Answer 38

The concept that Earth was shaped by

catastrophic events of a short-term nature.

Question 39

Uniformitarianism

Answer 39

The concept that the processes
that have shaped Earth in the geologic past are essentially
the same as those operating today.