Clues to Earth Past

1. Fossil:

Are the remains, imprints, or traces of prehistric organisms.

2. Permineralized remains:

Are fossils in which the spaces inside are filled with minerals from groundwater.

3. Carbon film:
When a thin film of carbon residue is left, forming silhouette of the original organism.

4. Mold:
A type of fossil that forms in rock when a organism with hard part, decays or dissolves, and leaves, and leaves a cavity in rock.

5. Cast:
A type of body fossil that forms when crystals fill a mold or semiments wash into a mold and harden into rock.

6. Index Fossils:

Are the remains of species that exist on Earth to relatively short periods of time, were abundant, and were widespread geographically.

7. Principle of Superposition:

States that in undisturbed rocks layers, the oldest rocks are on the bottom and the rocks become progressively younger toward the top.

8. Relative Age:
It is age in comparison to other things.

9. Unconformity:

Gaps in rock.

10. Absolute Age:

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

11. Radioactive Decay:

Process in which some isotopes break down into other isotopes and particles.

12. Half-life:

Is the time it takes for half of the atoms in the isotopes to decay.

13. Radiometric Dating:

Process used to calculate the absolute age of rock by measuring the ratio of parent isotope to daughter product in a mineral and knowing the half-life of the parent.

14. Uniformitarianism:

Principle stating that Earth processs ocurring today are similar to those that ocurred in the past.