Geol 102 Exam 1 (CH 1-3)

Physical Geology

Physical geology examines the structure, composition, and processes that affect the Earth today.

Historical Geology

Historical geology addresses Earth’s origin and evolution, distribution of lands and seas through time, the growth and reduction of mountains, and the succes- sion of animals, plants, and other living things that lived in the ocean and on continents down through the ages.

Scientific Method

The scientific method is a systematic way to uncover answers to questions, solutions to problems, and evidence to prove or disprove ideas and beliefs.

Hypothesis

a proposed, testable explanation for a phenomenon that guides scientific research and experimentation

Theory

An hypothesis that survives repeated challenges and is supported by accumulating favorable evidence.

Scientific Law

Scientific law is the description of a naturally occurring phenomena in the worl; a set of observed facts.

Absolute Age

The actual age, expressed in years, of a geological material or event.

Half-Life

The time required for one‐half of the original quantity of radio- active atoms to decay.

Relative Age

The placing of an event in a time sequence without regard to the absolute age in years.

Plate Tectonics

The theory that explains the tectonic behavior of

the crust of the Earth in terms of several moving plates that are formed by volcanic activity at oceanic ridges and destroyed along great ocean trenches.

Lithosphere

The rigid outer layer of Earth (roughly 100 km thick) that includes the crust as well as the uppermost part of the mantle.

Crust

The outer part of the lithosphere, which averages about 32 kilometers in thickness.

Mantle

a thick layer of the Earth located between the crust and the core

Asthenosphere

plastic, easily deformed layer of the mantle

Divergent Boundary

Where two or more plates move apart

Convergent Boundary

Where plates converge

Transform Boundary

Where plates grind past one another

Natural Selection

the process where organisms with helpful traits survive and reproduce more often, passing those traits to the next generation

Actualism

the principle that says natural laws do not change with time.

catastrophism

the history of life was marked by frightful catastrophes and each calamity completely extinguished life and was followed by the appearance of new animals and plants.

inclusions

fragments of one rock that appear in another

principle of cross-cutting relationships

the penetrating mineral vein, intruding rock mass, or fault must be younger than the rock body that has been penetrated.

principle of fossil succession

the characteristics and forms of ancient life are organized in such a way that the fossils are unique to specific intervals of geological time.

principle of inclusions

whenever two rock masses are in contact, the one containing pieces of the other will be the younger of the two.

principle of original horizontality

sediment is deposited in layers that are originally horizontal.

principle of original lateral continuity

a rock layer extends continuously in all directions until it thins out, encounters a barrier, or grades laterally into another type of sediment.

principle of superposition

in any sequence of undisturbed layers (or strata), the oldest layer is at the bottom, and successively younger layers are located at successively higher levels.

strata

any sequence of undisturbed layers

stratigraphy

the study of layered rocks, including their texture, composition, arrangement, and correlation from place to place.

unconformity

gap in the rock record produced by erosion

absolute geological dating

expresses, in years, the approximate actual age of rocks or geological events.

alpha particle

A particle equivalent to the nucleus of a helium

atom, emitted from an atomic nucleus during radioactive decay.

archaean eon

Pertaining to the division of Precambrian, begin- ning 3.8 billion years ago and ending 2.5 billion years ago.

atom

The smallest divisible unit retaining the characteristics of a specific element.

atomic mass

A quantity essentially equivalent to the number of neutrons plus the number of protons in an atomic nucleus.

atomic number

The number of protons in the nuclei of atoms of a particular element.

bentonite

A layer of clay, presumably formed by the alteration of volcanic ash.

beta particle

A charged particle, essentially equivalent to an elec- tron, emitted from an atomic nucleus during radioisotopic disintegration.

cambrian system

a sparsely fossiliferous sequence of rocks

carboniferous system

strata that included coal beds in north‐central England

cenozoic

the era we currently live in, which began about 66 million years ago

cretaceous

geological period that began 145 million years ago and ended 66 million years ago.

daughter element

new atom formed from radioactive decay

devonian system

outcrops near Devonshire, England

electrons

particles in the outer most shell of an atom that have a negative charge

element

a chemical building block that combines to form minerals

eons

A major division of the geological time scale

epochs

A chronologic subdivision of a geological period. All strata and other rocks that formed during an epoch constitute the series for that epoch.

eras

A major division of geological time, divisible into geological periods.

fission tracks

really small tunnels that were produced when high‐energy particles from atom nuclei were fired off during spontaneous fission

gamma radiation

Ultra high‐frequency electromagnetic waves

geochronology

The science of determining the age of rocks

hadean eon

the span of time from the planet’s origin to the beginning of the Archean

holocene series

composed of sediments and rocks formed after the retreat of Pleistocene glaciers.

isotopes

Atoms of an element that have the same number of pro- tons in the nucleus, the same atomic number, and the same chemical properties but different atomic masses because they have excess neutrons in their nuclei.

jurassic

strata of the Jura Mountains between France and Switzerland

mesozoic

a major geological time period that lasted from about 252 million to 66 million years ago

mississippian

Lower Carboniferous strata that are extensively exposed in the upper Mississippi River Valley

neogene system

includes the Miocene and Pliocene Series

neutrons

An electrically neutral (uncharged) particle of matter existing along with protons in the atomic nucleus of all elements except the mass 1 isotope of hydrogen.

ordovician system

geological system to encompass Sedgwick’s Upper Cambrian and Murchison’s Lower Silurian.

paleogene

A subdivision of Cenozoic that encompasses the Paleocene, Eocene, and Oligocene epochs.

paleozoic

a major geological time period that lasted from about 541 million to 251.9 million years ago

parent element

the original, unstable atom that undergoes radioactive decay before transforming into a new product called a daughter element

pennsylvanian

Upper Carboniferous strata that have been heavily mined for coal

periods

shorter units of eras; periods are divided into epochs

permian system

strata above carboniferous rocks in western russia

phanerozoic eon

The eon of geological time during which the Earth was populated by abundant and diverse life. covers the past 541 million

pleistocene

a geological epoch that lasted from about 2.58 million to 11,700 years ago, widely known as the last Ice Age.

precambrian

Pertaining to all of geological time and its corre- sponding rocks, which before the beginning of the Paleozoic Era.

proterozoic eon

spans the time interval from 2500 to 541 million years ago

protons

An elemental particle found in the nuclei of all atoms that has a positive electric charge and a mass similar to that of a neutron.

quaternary system

includes rocks and fossils of the Pleistocene Series, including sediments of the Pleistocene Ice Age

radioactivity

the natural process where unstable atoms break down and release energy as radiation

radioisotopic age-dating

Any of a group of methods of absolute age dating that relies on measurements of how much of a specific radioactive isotope remains in the rock following the rock’s for- mation or last heating event.

relative geological dating

places geological events, and the rocks repre- senting those events, in sequence

series

The time‐rock term representing the rocks deposited or emplaced during a geological epoch. A series is a subdivision of a system.

silurian system

fossil‐bearing strata in southern Wales

stage

The time‐rock unit equivalent to an age. A stage is a subdi- vision of a series.

system

The time‐rock unit that was deposited or emplaced during a given geological period. For example, the Cambrian System formed during the Cambrian Period

time units

increments of time called geochronologic units

time-rock units

The rocks formed during a particular unit of geological time.

triassic system

the three‐fold division of rocks of this age in Germany

alluvial fan

forms when stream-transported sediment is deposited abruptly from flowing streams in a mountainous area onto a flat plain

angular unconformity

older angled strata and younger more nearly flat‐lying strata are separated by an erosional surface.

arkoses

sandstones containing 25% or more feldspar

barrier islands

long, narrow sand islands that run parallel to the mainland coast and act as natural buffers against ocean storms

biofacies

distinguishing characteristics within a rock body that contain fossil assemblages

biostratigraphic correlation

links rock units by similarity of their fossils or fossil zonations.

cement

another bonding material, a chemical precipitate that crystallizes in the voids between grains following deposition.

chronostratigraphic correlation

links rock units by age equivalence, determined by fossils or radioactive dating methods.

clasts

the individual particles or fragments derived from the breakdown of existing rock

continental shelves

the submerged edges of the continents that have clear continuity with the adjacent coastal plains

continental slopes

areas of the ocean floor that extend from the seaward edge of the continental shelves down to the ocean depths

correlation

Determining the equivalence of rock bodies in different localities

craton

the stable interior of a continent, undisturbed by tectonic events for perhaps 500 mil- lion years or more

cross-bedding

an arrangement of beds or laminations in which one set of layers is inclined relative to the others

deltas

accumulations of sediment that form where a stream flows into a body of relatively quiet water, such as an ocean or a lake

discharge

the quantity of water passing a point on the stream in a given time

disconformity

parallel strata are separated by an erosional surface.