Placing GEOLOGIC EVENTS in sequential based on their ORDER in the rock record (ex.younger, older)

Assigning a SPECIFIC DATE to an object, usually using radioactive elements.(ex. 250 MYA)

Time required for HALF of a radioactive sample to Decay

Using the HALF-LIFE of RADIOACTIVE ELEMENTS to DETERMINE the AGE of material.

BEGINNING of the EARTH- 88% of Earth's History

• Most of the CONTINENTS were COVERED in warm, shallow SEAS- (lots of sea life)

• Ended with a MASS EXTINCTION- killed 90% of marine organisms

• DINOSAURS roamed the earth

• SMALL MAMMALS and BIRDS appeared

• Ended with a MASS EXTINCTION that KILLED OFF the DINOSAURS

• Began 65 million years ago and still continues TODAY!!

-AGE OF MAMMALS- live in land, air and the sea.

-HUMANS evolve

Happens when as many as 90% of ORGANISMS DIE

Happens when as many as 90% of ORGANISMS DIE

OLDEST LAYERS are ON BOTTOM & YOUNGEST LAYERS are on TOP

Rock layers are ORIGINALLY DEPOSITED in HORIZONTAL LAYERS.

FAULTS or IGNEOUS INTRUSIONS are YOUNGER than the rock that they cut through

A gap in the rock record, usually caused by erosion

Geologic Time divisions from largest to smallest