A
fossils of species that lived on Earth for short periods of time and were abundant and widespread geographically
index fossils
the time it takes for half of the atoms in an isotope to decay
half-life
a process that uses the properties of atoms in an isotope to decay
radioactive decay
states that Earth processes today are similar to those that took place in the past
uniformitarianism
the process of calculating the absolute age of a rock by measuring the amounts of parent and daughter materials in a rock and by knowing the half-life of the parent
radiometric dating
states that for undisturbed rocks, the oldest rocks are on the bottom and the rocks become younger and younger toward the top
principle of superposition
the order of events and the relative age of rocks is determined by examining the position of rocks in a sequence
relative dating
the impression in a rock left by an ancient organism
mold
gaps in rock layers that develop when agents of erosion remove existing rock layers
unconformities
fossil formed when an outline of the original organism is formed from left-over carbon
carbon film
a fossil copy of an organism made when a mold of the organism is filled with sediment or mineral deposits
cast
______ dating uses the properties of atoms in rocks and other objects to find their ages.
absolute
A _______ is the cavity left behind in the rock after an organism's hard part has decayed.
mold
An unconformity is a _______ of rock.
missing layer
The _______ parts of organisms are most likely to become fossils.
hard
Preserved animal tracks are called ______ fossils.
trace
is measured in half-lives
radioactive decay
Fossils up to 50,000 years old can be dated with _______.
carbon-14
A ________ may tell a paleontologist when, where, and how an organism lived.
fossil
Fossils are the _____, imprints, or traces of once-living organisms preserved in rock.
remains
Rock layers are correlated if they both contain the same ______.
fossils
What classification of unconformity occurs when sedimentary rock overlies igneous rock?
nonconformity
relative dating
With ______ dating, a rock's exact age can be determined, whereas with ______ dating, a rock's age is compared to the ages of other rocks.
absolute, relative
Radiocarbon dating can be used to determine the age of what type of materials?
organic materials