Earth's History

absolute dating

any method of measuring the age of an event in years.

Radiometric Dating

the process of measuring the absolute age of geologic material by measuring the concentrations of radioactive isotopes and their decay products.

Law of Cross-cutting

any feature that cuts across a rock or layer must be younger than the rock or layer it cuts across

Law of Inclusion

Rock fragments must be older than the rock containing the fragments

accretion

when small bodies of rock and metals come together due to gravitational contraction.

Catastrophism

sudden changes to Earth. A result of unpredictable natural disasters.

Uniformitarianism

gradual changes on Earth. Same slow changes over time due largely to erosion and deposition.

Fossil

The preserved remains or traces of a once-living organism, providing evidence of past life on Earth.

Trace Fossil

a type of fossil that provides evidence of the activities of ancient organisms.

Climate

The long-term weather conditions of an area, including temperature, precipitation, and wind patterns.

Ice Core

A cylindrical sample of ice obtained by drilling through ice caps or sheets, used to study past climates and atmospheric conditions.

Relative Dating

determining the order of past events, whether and object or event is older or younger than other objects or events.

Superposition

The principle stating that in undisturbed rock layers, the oldest rocks are found at the bottom, and the youngest rocks are found at the top.

Unconformity

A gap in the geologic record due to erosion or non-deposition of rock layers, representing a period of missing time in the geological history.

Geologic Column

A representation of the rock layers and their relative ages in a specific area, providing a chronological sequence of Earth's history.

radioactive decay

the process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element.

Half-Life

the length of time required for half of the radioactive atoms in a sample to decay.

Law of Superposition

states that younger layers of rock are deposited on top of older layers

Principle of Lateral Continually

layers of sediment initially extend laterally in all directions;

Tilting

the slanting of rock layers from internal forces in the Earth.

isotope

atoms of the same element that have different number of neutrons.

intrusion

an igneous rock layer formed when magma pushes into other rock and hardens.

parent isotope

the isotope that undergoes radioactive decay.

folding

the bending of rock layers due to stress.

daughter isotope

the stable isotope produced by the radioactive decay of the parent isotope.

index fossil

a fossil that is found in the rock layers of only one geologic age, but found worldwide, and that is used to establish the age of the rock layer.

fault

a crack in Earth's crust.

Geology

the study of Earth's physical structure, its history, and the processes that act on it.

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