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Understanding Rock Formation: Types, Composition, and Textures

Explore the fascinating world of geology and discover how rocks are formed, distributed, and their unique compositions and textures. Learn about the three main types of rocks: igneous, metamorphic, and sedimentary. Delve into the formation processes, such as the solidification of molten rock, the metamorphism under heat and pressure, and the sedimentation that builds layered sedimentary rocks. Uncover the geological factors like plate tectonics that influence rock distribution on Earth. This overview provides key insights into the nature of rocks and their properties.

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Understanding Rock Formation: Types, Composition, and Textures

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  1. Ashley Atanasoff Geology How are rocks formed and distributed and what is their composition and texture like?

  2. Igneous Rock Formation • formed when hot molten rock solidifies • 2 types: intrusive and extrusive • intrusive- formed when magma is trapped deep inside the earth, cools slowly over thousand or millions of years until it solidifies • extrusive- formed when magma exits and cools outside the earth’s surface, it cools and solidifies almost instantly from the exposure to the cool temperature of the atmosphere

  3. Metamorphic Rock Formation • formed when rocks are heated and put under great pressure • not made from melted rock (rocks that melt will form igneous rock) • 2 types: contact and regional • contact- hot magma intrudes into cooler rock • regional- pressure and temperature change over distance

  4. Sedimentary Rock Formation • rivers carry pieces of broken rock as it flows • when a lake or sea is reached, the rock pieces settle to the bottom • the deposited pieces build up in layers (this is called sedimentation) • the weight of the sediments on top squish the sediments on the bottom (this is called compaction)

  5. Rock Distribution • the distribution of rocks is mostly due to plate tectonics • i.e. divergent plate boundaries, subduction zones, etc. • can be carried by wind, water, or glaciers

  6. Igneous Rock Composition • felsic- have a lot of feldspars and silica • intermediate- between felsic and mafic • mafic- have a lot of magnesium and iron with less silica • ultra mafic- even more magnesium and iron with even less silica

  7. Metamorphic Rock Composition • of foliated- composed of more than one mineral • of non-foliated- composed of only one mineral

  8. Sedimentary Rock Composition • clastic- made of rock/mineral pieces or fragments • chemical- made of crystals interlocked with each other • biological- made of an accumulation of organic material

  9. Igneous Rock Textures • phaneritic- made up entirely of crystals that are visible to the eye • aphanitic- made up entirely of small crystals that are not visible to the eye • porphyritic- both aphanitic and phaneritic • pegmatitic- made up entirely of large crystals • glassy- non-crystalline structure of the rock • vesicular- porous structure • breccia- broken, angular fragments of mixed compositions

  10. Metamorphic Rock Textures • slatey texture- fine-grained • phyllitic texture- contain mica-crystals • schistose texture- coarse grains • gneissic texture- coarsest grains

  11. Sedimentary Rock Textures • of clastic- grains are barely or not at all visible • of chemical- made up of crystals • of biologic- remains of organisms, shells, etc.

  12. Bibliography • http://hyperphysics.phy-astr.gsu.edu/hbase/geophys/mincomp.html • http://faculty.chemeketa.edu/afrank1/rocks/metamorphic/mtexture.htm • http://facweb.bhc.edu/academics/science/harwoodr/geol101/Labs/Sediment/index.htm • http://www.bbc.co.uk/bitesize/ks3/science/environment_earth_universe/rock_cycle/revision/5/ • http://www.nationalatlas.gov/articles/geology/types/sedimentary.html • http://www.pitt.edu/~cejones/GeoImages/2IgneousRocks/IgneousCompositions.html • http://jersey.uoregon.edu/~mstrick/AskGeoMan/geoQuerry14.html • http://geology.com/rocks/igneous-rocks.shtml • http://www.tulane.edu/~sanelson/eens212/metatexture.htm

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