Uniformitarianism / Geologic Dating

Front

Uniformitarianism

Back

The idea that the geological processes that happen today (volcanoes, faulting, erosion) have always happened on Earth.

Front

Original horizontality

Back

When sediments are laid down, they are horizontal. If rock layers are not horizontal, something happened to them.

Front

Law of Superposition

Back

In undisturbed rock layers, the oldest is at the bottom and the youngest is on the top.

Front

Folding

Back

Convergent boundary squeezes the rock and bends it.

Front

Faulting

Back

Break in the rock.

Front

Uplifting

Back

When some layers of rock are lifted from below.

Front

Intrusions

Back

Cracks in rock fill with magma which hardens.

Front

Unconformity

Back

When layers are eroded leaving a jagged top layer (missing rock).

Front

Cross Cutting Relationship

Back

When layers of rock are cut across by folding, faulting, uplifting, or erosion.

Front

Radiometric Dating

Back

Finding the absolute age by testing how much of a radioactive element is still present.