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