martes, 12 de abril de 2011

Clues to Earth's Past

1. Fossils:
are the remains, imprints, oe traces of prehistoric organism.

2.Permineralized remains:
are fossils in which thespaces inside are filled with minerals from groundwater.

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

4. Mold:
 is the hard part might decay or dissolve, leaving behind a cavity in the rock.

5. Cast:
is the mineral-rich water or other sediment might enter the cavity.

6. Index Fossils:
are the remains of species that existed on Earth for relatively short periods of time, were abundant, and were widespread geographically.

7. Principle of Superposition:
undisturbed layers of rocks.

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

9. unconformities:
are gaps in rock sequences.

10. Absolute Age:
is the age, in years, of a rock or other object.

11. Radioactive Decay:
is the process of breaking down.

12. Half-Life:
is the time it takes for half of thecarbon -14 is 5,730 years.

13. Radiometric Dating:
 is the process of the absolute age of rock.

14.Uniformitarianism:
Is a principle is often paraphrased.

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