Age of the Earth

3. A supercontinent containing all of Earth's land that existed about 225 million years ago.
4. a type of rock that forms from the cooling of molten rock at or below the surface
6. a space in a rock that has the shape of the remains of a living thing that once occupied that space.
9. a rock that forms from compressed or cemented layers of sediment
11. Current era; development of large mammals; Periods of Ice Ages played a role in creating geological features
13. A long cylinder of ice obtained from drilling through ice caps or ice sheets; used to study past climates.
15. The age of a rock given as the number of years since the rock formed.
16. the age of an object in relation to the ages of other objects
17. Increased complex life forms: dinosaurs, small mammals; another mass extinction
18. remains of species that existed on Earth for a relatively short period of time, were abundant and widespread geographically, and can be used by geologists to assign the ages of rock layers
20. A trace of an ancient organism that has been preserved in rock.

1. Formation of Pangea; Life developed rapidly: invertebrates, fish and ferns, amphibians; Mass extinction
2. The top rock layer and its fossils are the youngest and the bottom is the oldest.
5. The age of a rock compared to the ages of rock layers
7. first 4 billion years of earths history, very primitive life forms: one-celled organisms, bacteria, jellyfish
8. A type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions.
10. an immeasurably long period of time
12. forms when entire organisms or parts of organisms are prevented from decaying by being trapped in rock, ice, tar, or amber.
14. a scientific method of determining the age of an artifact
19. When molten rock from the Earth's interior squeezes into existing rock and cools.