rock: Quick Facts

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Diagram of the rock cycle showing transitions between rock at Earth's surface, sediment, igneous rocks, metamorphic rocks, and sedimentary rocks, with arrows indicating processes like erosion, deposition, burial, melting, and uplift.

Eight labeled rock samples are shown, including black glassy obsidian, speckled porphyry, striped calico sandstone, shell-filled coquina limestone, coarse breccia, layered banded gneiss, pale green fibrous talc schist, and greenish serpentine.

A chart categorizes common textural terms for rocks by grain size in millimeters, dividing them into igneous and metamorphic, sedimentary, and pyroclastic types, with terms like phaneritic, sand, silt, breccia, and ash shown in relation to size.

Two diagrams compare sediment sorting: the left shows poorly sorted sediment with mixed sizes and shapes, while the right shows well-sorted sediment with uniform, similarly sized grains.

A line graph displays the distribution of dry bulk densities for various rock samples, with density values on the x-axis and percent of total samples on the y-axis. Most samples cluster around 2.63 grams per cubic centimeter. An inset graph shows cumulative percentage distribution, and a text box summarizes statistics such as mean, median, mode, and sample size.

$Diagram showing how rock deformation changes with increasing confining pressure, progressing from extension fracture and brittle fracture to brittle faulting, ductile faulting, and finally plastic flow.$

$Graph showing typical stress-strain curves for brittle, moderately ductile, and ductile rock materials, with X marks indicating fracture points for each type. Axes display stress versus strain, and annotations highlight yield points, permanent deformation, and recoverable regions.$

A magnetic hysteresis curve graph with magnetization J on the vertical axis and external field Hex on the horizontal axis, showing a looped curve with key points labeled for saturation magnetization Js, remanent magnetization Jr,sat, and coercive fields Hc and Hc,r.

Soil regions of the United States, showing areas covered by soil orders of the U.S. Soil Taxonomy. Click on a soil order for a descriptive entry on properties and uses.

The rock cycle: How different types of rock are formed

Learn how the earth keeps itself fresh and new and how the chemical properties of zircon determine the age of the earth

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Topics

metamorphic rock sedimentary rock igneous rock assimilation basement rock country rock source rock wall rock Moon rock geopressured fluid soil Meteorite mineral deposit tektite Dust Why Is Earth’s Axis Tilted?Equator Climate plate tectonics What Is Earth’s Velocity?

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Key People

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Gabriel-Auguste Daubrée

French geochemist

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Hans Cloos

German geologist

Day, Arthur L.

Arthur L. Day

American geophysicist

Basalt sample returned by Apollo 15, from near a long sinous lunar valley called Hadley Rille. Measured at 3.3 years old.

(Bed) Rocks and (Flint) Stones

Cross section of Earth showing the core, mantle, and crust

Everything Earth

Basalt sample returned by Apollo 15, from near a long sinous lunar valley called Hadley Rille. Measured at 3.3 years old.

(Bed) Rocks and (Flint) Stones

ore. iron ore minerals, rock, metal, metallic iron

Rocks, Minerals, and More Quiz

Cross section of Earth showing the core, mantle, and crust

The Solid Earth Quiz

27 True-or-False Questions from Britannica’s Most Difficult Science Quizzes