chapter 8 Flashcards
A(n) _________ is a contact in which an erosional surface on a pluton or metamorphic rock has been covered by sedimentary (or volcanic) rock.
disconformity, basal conglomerate, nonconformity, or angular unconformity.
nonconformity
The _____ 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.
actualism
fossils are common in ___.
sedimentary rocks
___ are subdivisions of eras.
periods
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.
isotopes
The ___ of a radioactive material is the time it takes for a given amount of radioactive isotope to be reduced by half.
half life
In radioactive decay a(n) _______ emission is the emission of two neutrons and two protons from a nucleus.
alpha
______ denotes the vast amount of time that precedes the Paleozoic Era.
Precambrian
The _____ ended with the greatest mass extinction ever to occur on Earth.
Paleozoic Era
Uranium-238 ultimately decays to _____ -206
lead
In geology, __ usually means determining time equivalency of rock units.
correlation
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 __.
superposition
The proportional amount of atoms that decay with time _____ by the high pressures and temperature of Earth’s interior.
is not changed at all
The principle of ___ states that an original sedimentary layer extends laterally until it tapers or thins at is edges
lateral continuity
______ first pointed out that fossil species succeed one another through successive layers of sediment in a predictable order.
W.S. Smith
how old is the earth
4,500,000,000 to 4,600,000,000 yrs old
In a(n) __________ the erosional contact represents missing rock strata and separates sedimentary beds that are parallel.
disconformity
In the radioactive decay process of __ decay, an electron is emitted from the nucleus of the parent isotope.
beta
A(n) _______ is an erosional surface that represents a gap in the geologic record.
unconformity
The truncation of bedding where sedimentary rock layers abut a granite pluton suggests a(n) ______.
intrusive contact
In the radioactive decay process of electron capture a(n) ___ in the nucleus captures an orbiting electron.
proton
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?
1 billion
Alvarez and others proposed a hypothesis that dinosaur extinction occurred because __.
one or more asteroids impacted Earth, resulting in environmental change
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.
cross-cutting relationships; younger
The principle of ______ states that fragments included in a host rock must be _______ than the host rock.
inclusion; older than
The relative-dating principle of __ states that fragments included in a host rock are older than the host rock.
inclusion
Radiocarbon dating is useful in dating an event that occurred in the past ________ years.
40 thousand
The ____ is based upon the observation that fossil species succeed one another through layers in a predictable order.
principle of faunal succession
_______ is the spontaneous nuclear change of isotopes with unstable nuclei.
radioactive decay
Isotopic dating has shown that the Precambrian took up ______% of all geologic time
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