Unit 3 Earth's History Vocabulary

Uniformitarianism

• A principle that states younger rocks lie above older rocks if the layer is undisturbed
• an ordered arrangement of rock layers that is based on the relative ages of the rocks and in which the oldest rocks are at the bottom
• A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
• A principle that geologic processes that occurred in the past can be explained by current geological processes

Fossil

• The death of every member of a species
• The history of life in the geological past as indicated by the traces or remains of living things
• The process by which individuals that are better adapted to their environment survive and reproduce more successfully than less well adapted individuals
• The trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock

Ice core

• A long cylinder of ice obtained from drilling through ice caps or ice sheets and used to study past climates
• an ordered arrangement of rock layers that is based on the relative ages of the rocks and in which the oldest rocks are at the bottom
• A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
• A principle that geologic processes that occurred in the past can be explained by current geological processes

Trace fossil

• The remains of an organism that lived long ago, most commonly preserved in sedimentary rock
• The death of every member of a species
• A fossilized structure, such as a footprint or a coprolite, that formed in sedimentary rock by animal activity on or within soft sediment.
• A principle that geologic processes that occurred in the past can be explained by current geological processes

Climate

• A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
• The weather conditions in an area over a short period of time
• A principle that geologic processes that occurred in the past can be explained by current geological processes
• The weather conditions in an area over a long period of time

Absolute dating

• A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
• A method of determining the absolute age of an object by comparing the relative percentages of a radioactive parent isotope and a stable daughter isotope.
• Any method of measuring the age of an event or object in years.
• The time required for half of a sample of radioactive isotope to break down by radioactive decay to form a daughter isotope

Half-life

• A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
• The history of life in the geological past as indicated by the traces or remains of living things
• A principle that geologic processes that occurred in the past can be explained by current geological processes
• The time required for half of a sample of radioactive isotope to break down by radioactive decay to form a daughter isotope

Radioactive decay

• The process in which a radioactive isotope tends to break down into a stable isotope of the same or another element
• The time required for half of a sample of radioactive isotope to break down by radioactive decay to form a daughter isotope
• A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
• The history of life in the geological past as indicated by the traces or remains of living things

Radiometric dating

• A method of determining the absolute age of an object by comparing the relative percentages of a radioactive parent isotope and a stable daughter isotope.
• The time required for half of a sample of radioactive isotope to break down by radioactive decay to form a daughter isotope
• A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
• The history of life in the geological past as indicated by the traces or remains of living things

Superposition

• an ordered arrangement of rock layers that is based on the relative ages of the rocks and in which the oldest rocks are at the bottom
• A long cylinder of ice obtained from drilling through ice caps or ice sheets and used to study past climates
• A principle that states younger rocks lie above older rocks if the layer is undisturbed
• The history of life in the geological past as indicated by the traces or remains of living things