Uniformitarianism - Geologic processes that occur today are similar to those that have occurred in the past., Relative-age dating - A method that shows the order in which geologic events occurred without giving the actual age., Absolute age - The actual age of an event or object in years., Strata - Layers of rock that form from compressed sediment over time., Superposition - In undisturbed rock layers, the oldest rocks are at the bottom and the youngest are at the top., Original horizontality - Sedimentary rock layers are originally deposited in flat, horizontal layers., Lateral continuity - Sedimentary layers extend horizontally in all directions until they thin out or reach a barrier., Inclusions - Pieces of one rock unit that are contained within another are older than the surrounding rock., Cross-cutting relationships - If one geologic feature cuts across another, it is younger than the feature it cuts., Fossil - The preserved remains or traces of ancient living things., Fossil record - The collection of fossils and their placement in chronological order in rock layers., Mass extinction - Times when many species on Earth died or became extinct within a relatively short period of time., Erosion - The process of wearing down and carrying away rocks by wind, water, or ice., Weathering - The breaking down of rocks at Earth’s surface into smaller pieces., Sediment - Small pieces of rock that are carried by wind, water, or gravity and deposited in new locations., Geologists - Scientists who study Earth, rocks, and the processes that shape them., Sedimentary Rock - Rock formed when layers of sediment are compressed and cemented together., Igneous Rock - Rock formed when magma or lava cools and hardens., Unconformities - Surfaces where rock has eroded away, producing breaks, or gaps, in the rock record., Angular Unconformity - When horizontal layers of sedimentary rock are later laid down on top of tilted, eroded layers., Disconformity - When a horizontal layer of sedimentary rock overlies another horizontal layer of sedimentary rock that has been eroded., Nonconformity - When a layer of sedimentary rock overlies a layer of igneous or metamorphic rock, such as granite or marble., Correlation - The matching of rock layers or fossils exposed in one geographic region to similar layers or fossils exposed in other geographic regions., Index Fossils - Fossils that represent species that existed on Earth for a short length of time, were abundant, and inhabited many locations., Key Bed - A rock or sediment layer used as a marker. Using the principle of superposition, geologists know that the layers above a key bed are younger than the layers below it., Geologic Time Scale - A model of Earth’s history from its origin 4.6 billion years ago to the present. Time units are thousands and millions of years long., Eon - The largest unit of geologic time., Era - Subdivisions of eons., Period - Subdivisions of eras., Epoch - Subdivisions of periods.,

Level 1 8-2

Print
Embed

Leaderboard

Visual style

Options

Switch template

Continue editing: ?