Chapter 4: Fossils & Relative Age

Fossil

The preserved remains or evidence of ancient living things

Catastrophism

the idea that conditions and organisms on Earth change in quick, violent events;

sudden changes

Uniformitarianism

the idea that geological processes that have occurred in the past will continue to occur and change conditions and organisms on Earth slowly;

gradual changes

Carbon Film

the fossilized carbon outline of an organism or part of an organism

Mold

the impression in a rock left by an ancient organism

Cast

a fossil copy of an organism made when a mold of an organism is filled with sediment or mineral deposits

Trace Fossil

the preserved evidence of the activity of an organism

Preserved Remains

actual remains or original tissues of the organisms are fossilized

Mineral Replacement

fossils formed when minerals in groundwater replace the tissues of dead organisms (sometimes called petrification or petrified fossils)

Paleontologist

scientist who studies fossils

Relative Age

the age of rocks and geological features compared with other rocks and features nearby

Superposition

the principle that in undisturbed rock layers, the oldest rocks are on the bottom

Inclusion

a piece of an older rock that becomes part of a new rock

Cross-cutting

when one geological feature, such as magma, rock, or faults, cuts into or across existing rock

Intrusion

a piece of rock or other geological feature that is cross-cutting, and is younger than the surrounding rock

Unconformity

a surface where rock has eroded away, producing a break, or gap in the rock record

Correlation

matching rocks and fossils from separate locations

Index Fossils

a representation of a species that existed on Earth for a short length of time, were abundant, and inhabited many locations

Fossil Record

made up of all of the fossils ever discovered on Earth

Geological Time Scale

a chart that divides the Earth's history into different time units

Extinction

occurs when the last individual organism of a species dies

Biological Evolution

the changes over time in populations of related organisms

Cladogram

a branched diagram that shows the relationships among organisms, including common ancestors

Common Ancestor

an ancient organisms or species that two or more modern species share a relationship with and have evolved from