Index Fossils
A fossil of an organism that existed for only a short period of geologic time and lived in many places.
Absolute dating
The actual age, in years, of a rock or fossil.
Relative dating
The age of an object or event in comparison to another object or event.
Carbon-14 dating
Carbon-14 is another radioactive substance used for finding age.
Law of superposition
States that in undisturbed sedimentary rock layers, older layers of rock lie under younger rock layers.
Radioactive dating
Measures the age of a material by comparing the amount of a radioactive substance with the amount of its decay product.
Uranium
A radioactive element that decays in lead.
Fossil
Are the preserved remains or evidence of organisms that lived in the distant past.
Extinct
A species when there are no more individuals of that species living on earth.
Geology
The study of Earth's history, processes, and structures.
Ice-cores
Is a cylinder of ice removed from an ice sheet, a deep deposit of ice and snow.
Erosion
A process by which weathered rock is picked up and moved to a new place which changes earth surface.
Unconformity
A gap in a rock layer record.
Tectonic plates
The lithosphere broken up into sections.
plate boundary
The region where 2 tectonic plates meet.
Seafloor spreading
Where 2 oceanic plates move apart, magma flows up into the space between the plates. The magma hardens to form new oceanic crust.
Fault
The break, or crack, in Earth's surface along which movement occurs.
Folding
Rock layers are squeezed together and pushed upward to form folds, or ripples in the crust forming mountains.
Uplift
The upward movement of rock layers. This occurs where 2 continental plates collide.
Magma
Melted rock beneath Earth's surface.
Lava
Melted rock that reaches Earth's surface.
Geologic evolution
The process of the Earth changing over time.