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  1. Rock | Definition, Characteristics, Formation, Cycle, Classification ...

    Apr 3, 2025 · Rock, in geology, naturally occurring and coherent aggregate of one or more minerals. Such aggregates constitute the basic unit of which the solid Earth is composed and typically form recognizable and mappable volumes. The three major classes of rock are igneous, sedimentary, and metamorphic rock.

  2. Geology | Definition, Examples, Rocks, Study, Importance, & Facts ...

    Geology, the fields of study concerned with the solid Earth. Included are sciences such as mineralogy, geodesy, and stratigraphy. Geology also explores geologic history, which provides a conceptual framework and overview of Earth’s evolution.

  3. rock summary | Britannica

    rock, In geology, a naturally occurring and coherent aggregate of minerals. The three major classes of rock—igneous, sedimentary, and metamorphic—are based on the processes that formed them.

  4. Rock - Structure, Texture, Composition | Britannica

    Apr 3, 2025 · Rock - Structure, Texture, Composition: Physical properties of rocks are of interest and utility in many fields of work, including geology, petrophysics, geophysics, materials science, geochemistry, and geotechnical engineering.

  5. sedimentary rock - Encyclopedia Britannica

    sedimentary rock, rock formed at or near Earth’s surface by the accumulation and lithification of sediment (detrital rock) or by the precipitation from solution at normal surface temperatures (chemical rock).

  6. Igneous rock | Characteristics, Examples, Formation, & Types

    Mar 6, 2025 · igneous rock, any of various crystalline or glassy rocks formed by the cooling and solidification of molten earth material. Igneous rocks constitute one of the three principal classes of rocks, the others being metamorphic and sedimentary.

  7. Geology - Earth Composition, Rocks, Minerals | Britannica

    Geology - Earth Composition, Rocks, Minerals: As a discipline, mineralogy has had close historical ties with geology. Minerals as basic constituents of rocks and ore deposits are obviously an integral aspect of geology.

  8. Texture | Geology, Description, Examples, & Facts | Britannica

    Texture, in rocks, the size, shape, and arrangement (or fabric) of the mineral grains and crystals. Also important in rock texture are the extent of homogeneity (i.e., uniformity of composition throughout) and the degree of isotropy (i.e., uniformity in all directions of such properties as

  9. Alkaline rock | Igneous, Volcanic, Magma | Britannica

    Alkaline rock, any of various rocks in which the chemical content of the alkalies (potassium oxide and sodium oxide) is great enough for alkaline minerals to form. Such minerals may be unusually sodium rich, with a relatively high ratio of alkalies to silica (SiO2), as in the feldspathoids.

  10. Stratification | Types, Causes & Effects | Britannica

    stratification, the layering that occurs in most sedimentary rocks and in those igneous rocks formed at the Earth’s surface, as from lava flows and volcanic fragmental deposits. The layers range from several millimetres to many metres in thickness and vary greatly in shape.

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