CLUES TO EARTH"S PAST

Fossil:

are the remains, imprints, or traces of prehistoric organism.

Permineralized:

are fossils in wich the spaces in side are filled with minerals.

Carbon film:

is a thin carbon residue is left, forming a silhouette of the original organism.

 

Mold:

the hard part of a might decay or dissolve, leaving behind a cavity in the rock.

Cast:

mineral-rich water or other sediment might enter the cavity, form a new rock, and produce a copy.

Index Fossil:

are the remains of especies that existed on earth for relatively periods of time.

Principle super Deposition:

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

Relative Age:

it age comparison to other things.

unconformity:

gaps in rock sequences.

Absolute age:

is the age, in years, of arock or other object.

Radioactive decay:

isotopes are unstable and break down into other isotopes and particles.

half-life:

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

Radiometric dating:

by measuring the radio parent isotope to the daughter product in a mineral knowing the half-life of the parent in many cases you can calculate the absolute age of the rocks.

Uniformitairanism:

states that eath processes occuring today are similar to those occured in the past