Geologic Time and Fossils

These flashcards cover key concepts related to geologic time, fossilization, and hydrology, providing definitions and explanations useful for exam preparation.

Eons and Eras

Major divisions in the geological time scale, where each eon and era has significant occurrences.

Paleozoic

Era when invertebrates first appeared.

Mesozoic

Era known for dinosaurs.

Cenozoic

Era in which mammals became prominent.

Relative age dating

Determining the order of events without assigning an actual date.

Numerical age dating

Assigning an actual numerical age to geological events.

Radioactive decay

Process of unstable isotopes breaking down into stable forms over time.

Half-life

The time required for half of a quantity of a radioactive isotope to decay.

Geologic time scale

A timeline used to represent the timing and relationships of events in Earth's history.

Uniformitarianism

The principle that the processes occurring today have been occurring throughout Earth's history.

Fossilization

The process of preserving remains of living organisms in geological formations.

Trace fossils

Fossilized evidence of activity rather than the organism itself.

Pseudofossils

Impressions or markings that resemble fossils but are not remnants of actual organisms.

Mass extinction

A rapid decrease in the biodiversity on Earth, often due to catastrophic events.

Aquifer

A geological formation that can store and transmit water.

Porosity

The measure of void spaces in a material; how much water can be held.

Permeability

The ability of a material to transmit fluids through its pore spaces.

Discharge of a stream

The volume of water flowing through a cross-section of a stream per unit time.

Oxbow lake

A U-shaped water body formed when a river meander is cut off.

Cone of depression

A lowered area of the water table surrounding a well due to excessive water extraction.