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| A type of rock that forms from the cooling of molten rock at or below the Earth's surface |
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| A type of rock that forms when particles from other rocks, or the remains of plants and animals, are pressed and cemented together |
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| A type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions |
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| A series of processes on the surface, and inside the Earth, that slowly change rocks from one kind to another |
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| A scientist who studes fossils to learn about organisms that lived long ago |
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| The age of a rock compared to the ages of other rocks |
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| The age of a rock given as the number of years since the rock formed |
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| In layers of horizontal sedimentary rock, each layer is older than the layer above it, and younger than the layer below it |
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| An igneous rock layer formed on the Earth's surface |
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| When magma pushes into a body of rock in the Earth's crust and hardens below the Earth's surface |
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| A break, or crack, in the Earth's crust |
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| A place where an old, eroded rock surface is in contact with a newer rock layer |
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| The breakdown of an unstable element, releasing particles and energy |
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| The time it takes for half of the atoms of a radioactive element to decay |
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| A record of geologic events and life forms in Earth's history |
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| One of three long units of time in the geologic time scale |
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| Units of geologic time into which geologists divide eras |
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| form at higher temperatures contain mineral assemblages that are rich in iron (Fe), magnesium (Mg), and calcium (Ca), creating a dark-colored rock |
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| Form at lower temperatures contain mineral assemblages rich in potassium (K), aluminum (Al), and sodium (Na), creating light-colored rocks |
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| The ultimate source of sediment is from older rocks that are exposed to the surface and are weathered and broken into smaller pieces. These pieces may be carried away a stream, bulldozed by a glacier, or picked up by the wind as their sediment load. Ultimately these sediments are deposited and may consolidate into a cohesive mass that we call clastic or fragmental sedimentary rock. |
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| Chemical sedimentary rock |
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Definition
| These rocks form from a water solution, and not from molten rock. Various salts (rock salt and gypsum) and some dolomites and limestones (by volume the most important chemical sediment) form this way. These rocks are called chemical sedimentary rocks. |
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| Bioclastic (bio-chemical) sedimentary rock |
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| Rock formed from material broken or arranged by animals, humans, or sometimes plants; a rock composed of broken calcareous remains of organisms. |
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