Fossils and Studying Earths Past Vocabulary

Fossil

The preserved remains, imprints, or traces of prehistoric organisms

Permineralized Fossil

When the small holes in an organims body are filled with minerals. This happens when water containing dissolved minerals is absorbed by an organisms body. When the water evaporates, the minerals are left behind. This only replaces some of the original body material with minerals.

Petrified Fossil

Occurs when an organisms body tissues are replaced by minerals

Carbonized Fossil

When an organism dies, the carbon in its body starts to break down. Some of the original material is decayed; however the carbon also forms a dark coating on top of the dead organism

Mold Fossil

Impression left by an organisms body or trace, like a footprint or burrow - the hard part may decay or dissolve , leaving behind a cavity in the rock

Cast Fossil

Copy of the original organims or trace. Mineral rich water or other sediment might enter the mold, form new rock, and produce a copy

Trace Fossil

Fossilized tracks, burrows and other evidence of the movement of organisms

Index Fossil

Remains of unique species that existed on Earth for relatively short periods of time, were abundant, and were widespread geographically

Body Fossil

An uncommon fossil of an organisms body or body parts

Original Remains

Part or all of the original organism remains, even after thousands or millions of years; include mummified fossils and remains preserved in amber, tar pits, or ice

Paleontologist

Scientist who study fossils

Principle of Superposition

In undisturbed layers of rock, the oldest rocks are on the bottom and the rocks become younger toward the top

Relative Age

Age of an object in comparison to ages of other objects. Can be found using the ordering of rock layers or with index fossils

Correlate

To match up

Relative Dating

Technique used by geologists to determine the ages of rock layers

Absolute Age

Is the age, in years, of a rock or other object

Absolute Dating

Also called radio metric dating or radioactive dating, measures the amount of radioactive material a rock near a fossil contains

Radioactive Decay

Process of unstable isotopes break down into other isotopes and particles

Half-Life

The time it takes for half of the atoms in the isotope to decay