Exam 8: Time and Geology

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

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

When the ____ came to a close,dinosaurs became extinct.

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.

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

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

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

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

In an unconformity the contact represents a gap in the geologic record.

Carbon-14 is created in the atmosphere by the nuclear reaction of neutron from the cosmic rays and _______ in the atmosphere.

Uniformitarianism reflects the belief among geologists that the Earth remains uniform and unchanging through time.

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

Isotopic dates from volcanic ash or lava flows layered between fossiliferous sedimentary rocks have been used to assign numerical ages to the geologic time scale.

______ denotes the vast amount of time that precedes the Paleozoic Era.

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

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

Uranium-238 ultimately decays to _____ -206.

So far,the oldest mineral found on Earth is approximately 4.4 billion years old.

The proportional amount of atoms that decay with time is only influenced by pressure and temperature.

The ___ Era began with the appearance of complex life,as indicated by fossils like trilobites.