Geology 2 Chapter 8

40 Thousand

Radiocarbon dating is useful in dating an event that occurred in the past ________ years

Inclusion, older than

The principle of ______ states that fragments included in a host rock must be _______ than the host rock

Superposition

When marine geologists collects a core of undeformed ocean-floor sediment, they know that the youngest layer is on the top of the core and the oldest is at the bottom because of the principle of __

Beta

In the radioactive decay process of __ decay, an electron is emitted from the nucleus of the parent isotope

Precambrian

__ denotes the vast amount of time that precedes the Paleozoic Era

Actualism

__ is the principle says that the same processes and natural laws that operated in the past are those we can actually observe or infer from observation as operating at present

Proton

In the radioactive decay process of electron capture a(n) ___ in the nucleus captures an orbiting electron

4.6 Billion

The Earth is approximately _____ years old.

Is not changed at all

The proportional amount of atoms that decay with time _____ by the high pressures and temperature of Earth's interior

Radioactive Decay

____ is the spontaneous nuclear change of isotopes with unstable nuclei

Half life

__ of a radioactive material is the time it takes for a given amount of radioactive isotope to be reduced by half

Lead

Uranium-238 ultimately decays to _____ -206

87

Isotopic dating has shown that the Precambrian took up ______% of all geologic time

W.S. Smith

_ first pointed out that fossil species succeed one another through successive layers of sediment in a predictable order.

Unconformity

___ is an erosional surface that represents a gap in the geologic record

Nonconformity

____ is a contact in which an erosional surface on a pluton or metamorphic rock has been covered by sedimentary (or volcanic) rock

Inclusion

The relative-dating principle of __ states that fragments included in a host rock are older than the host rock

1 billion

The half-life of the carbon 14 isotope is 5730 years. If there were 4 billion atoms of C-14 in a particular organism at the time it died, how many atoms of C-14 would there be in the remains of that organism 11,460 years after it died?

Correlation

____ usually means determining time equivalency of rock units

Cross-cutting relationships, younger

By the principle of __, the surface feature known as the Grand Canyon is ___ than the sedimentary formations that are exposed in the side walls of the Grand Canyon

Periods

__ are subdivisions of eras

Paleozoic Era

___ ended with the greatest mass extinction ever to occur on Earth

Lateral Continuity

principle of ___ states that an original sedimentary layer extends laterally until it tapers or thins at is edges

Alpha

In radioactive decay a(n) _______ emission is the emission of two neutrons and two protons from a nucleus

Intrusive Contact

The truncation of bedding where sedimentary rock layers abut a granite pluton suggests a(n) _____

Disconformity

In a(n) __________ the erosional contact represents missing rock strata and separates sedimentary beds that are parallel

Faunal Succcession

Principle of ___ is based upon the observation that fossil species succeed one another through layers in a predictable order

Sedimentary Rocks

Fossils are common in

Asteroids impacted Earth

Alvarez and others proposed a hypothesis that dinosaur extinction occurred because __

Isotopes

Our ability to assign an age to geological and archaeological materials is based on our ability to measure the relative abundance of radioactive ___ and their stable decay products