Exam 24: Geologic Time

The Mesozoic is a(n)

Geologic evidence places Earth's age at ______________ million years.

Layers of sediment,lava,and ash are originally laid down in a(n)______________ position.

Wood from an ancient stump has a ratio of carbon-14 to carbon-12 that is one-eighth that of new wood.About how old is the stump? (Carbon-14's half-life is 5730 years.)

If a rock sample contains uranium and lead,and lead-204 is present,then

Geologists think that Earth is how old?

The Paleocene is a(n)

Wood from an ancient stump has a ratio of carbon-14 to carbon-12 that is one-eighth that of new wood.About how old is the stump? (Carbon-14's half-life is 5730 years.)

New material filling a mold forms a ______________ of the original shell or bone.

The ______________ states that in a sequence of undisturbed sedimentary rocks,lavas,or ash,each layer is younger than the layer beneath it.

Geology's best tool for establishing absolute geologic time is

Sedimentary layer A is found above sedimentary layer B,and the two are separated by a horizontal layer of ash,C.Therefore,the order from oldest to youngest is

Geologists have principally used which class of rocks for radiometric dating?

When rocks and geologic events are placed in chronological order without regard to actual dates,______________ geologic time is obtained.

The Cretaceous is a(n)

The time before the Phanerozoic eon is collectively called ______________ time.

______________ fossils are those typical of a particular limited time segment of Earth's history.

Potassium-40,one of the six major radionuclides used for radiometric dating,decays to

The Phanerozoic eon and the Paleozoic era began about ______________ million years ago.

Geologists have principally used which class of rocks to establish the relative time scale?