definitions
represent species that existed on Earth for a short length of time, were abundant, and inhabited many locations.
index fossils
the oldest rock layer is at the bottom and the youngest is at the top
superposition
When an organism gets pressed to a rock and everything squeezes out until all that is left is a carbon outline
carbon film
a surface where rock has eroded away, producing a break, or gap, in the rock record.
unconformity
the preserved remains or evidence of ancient living things.
fossils
the numerical age, in years of a rock or an object.
absolute age dating
Sediments are deposited in large, continuous sheets in all lateral directions
lateral continuity
Replicas of organisms can form from minerals
mineral replacement
Younger sedimentary layers are deposited on top of older, horizontal layers that have been eroded.
disconformity
the idea that conditions and creatures on Earth change in quick, violent events.
Catastrophism
the principle that states, geologic processes that occur today are similar to those that have occurred in the past.
uniformitarianism
Sometimes rock layers are disturbed after they form and can become tilted or folded.
original horizontality
When an organism dies and the sediment around it hardens and leaves an impression of that organism
mold
Younger sedimentary layers are deposited on older igneous or metamorphic rock layer that have been eroded.
nonconformity
scientists who study fossils
paleontologist
atoms of the same element that have different numbers of neutrons
isotopes
When older rocks break the pieces can land in soft sediment or magma. As the sediment or magma hardens the old rock becomes part of the new rock.
inclusions
tracks, footprints, or nests
trace fossil
Sedimentary layers are deposited on top of tilted or folded sedimentary layers that have been eroded.
angular unconformity
the age of rocks and geologic features compared with other rocks and features nearby.
relative age dating
The process by which an unstable element naturally changes into another element that is stable.
radioactive decay
When rocks move along a fracture line, the fracture is called a fault. Faults cut against existing rocks. The feature that is cuts across is older
cross cutting
organisms in amber, tar, or ice
preserved remains
Geologists fill in the gaps of the rock record by matching rock layers or fossils from separate locations
correlation
the time required for half of the parent isotopes to decay into daughter isotopes.
Half-life