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A rock is a naturally occurring mass of inorganic or organic material that forms a significant part of the earth's crust.
A rock can also be defined as a solid substance that occurs naturally because of the effects of three basic geological processes: magma solidification; sedimentation of weathered rock debris; and metamorphism .
Process-oriented. Based on the rate of cooling of the igneous rocks
And their resultant grain size.
Texture - size, shape and arrangement of mineral grains in a rock.
Coarse grained - individual mineral grains can be seen which the naked eye. Rock must have cooled slowly to allow large crystals to develop.
Fine grained - mineral grains are present but are two small to be seem with the eye. Cooled rapidly before crystals had a chance to grow.
Vesicular - rock containing vesicles (gas holes). Always light weight. Example pumice.
Glassy - not composed of minerals at all but a true glass. Glasses are not crystalline!
Examples of Igneous Rocks Granite 1. Light color 2. Low specific gravity 3. Coarse grained 4. Forms on the continents deep underground Basalt 1. Dark color 2. High specific gravity 3. Fine grained 4. Forms at the surface, principally in the ocean basins, but also in isolated "hot spots" on the continents.
Pictorial Classification of Igneous Rocks http://geollab.jmu.edu/Fichter/IgnRx/Introigrx.html
Layered or stratified rocks formed at or near the earth's surface in response to the processes of weathering, erosion, transportation and deposition.
Sedimentary rocks are generally stratified, fine-grained or composed of fragments of older rocks from which these were derived, such as pebbles, sand, angular fragments of older rocks, broken shells, rounded mineral grains and alteration minerals such as clays.
May stratified because the sediments are laid down in horizontal layers called strata. ( one layer is called stratum)
May also contain fossil i.e: remains, prints or other indications of plants & animals found buried in rocks
Dipping sedimentary layers of rock, Rocky Mountains, Canada. http://www.geog.ouc.bc.ca/physgeog/contents/10f.html
Examples of Sedimentary Features and Landforms The Queen’s Throne- Utah http://www.uh.edu/~jbutler/physical/chapter7.html Narracoorte Caves, southeastern SA Stalactites (of mineral calcite). Biochemical and inorganic sedimentary limestone rocks.
The Ayers Rock is made up of arkose, a course-grained sandstone rich in feldspar at least 2.5 km thick. Uplifting and folding between 400-300 mya turned the sedimentary layers nearly 90 degrees to their present position. The surface has then been eroded.
Regional metamorphism : takes place during mountain building when rocks are metamorphosed
Contact metamorphism found in the vicinity of igneous intrusions & the high temperatures of magma heats the rock adjacent to these intrusions, causing recrystallization & growth of crystals
Pressure metamorphism : rocks are altered under high pressure associated with Earth movements (folding & faulting)
Examples of Metamorphic Rocks Slate is a fine grained metamorphic rock. Created by minor metamorphism of shale or mudstone . Rock is characterized by the foliation of its mineral grains which causes it to have cleavage that is parallel. Gneiss is a coarse grained metamorphized igneous rock. In this rock, you get the recrystallization and foliation of quartz , feldspars , micas , and amphiboles into alternating light and dark colored bands.
Harder and more compact than the rock they are made from.
Minerals are arranged in bands or recrystallised to form new or larger minerals
Foliated vs. Non-Foliated? The minerals grains in rocks subjected to extreme pressure often rearrange themselves in a parallel fashion, creating a foliated texture ( Image A - before metamorphism; Image B - after metamorphism).
Authored by James Hutton (1727–1797), the eminent 18th century gentleman farmer and founder of modern geoscience which depicts the interrelationships between igneous, sedimentary, and metamorphic rocks.
Upper part of the earth envisioned as a giant recycling machine; matter that makes up rocks is neither created nor destroyed, but is redistributed and transformed from one rock type to another.
James Hutton http://www.gennet.org/facts/hutton.html
Diagrammatic Representation of Rock Cycle http://www.science.ubc.ca/~geol202/rock_cycle/rockcycle.html
Research on the properties of granite, basalt, sandstone, clay and limestone: their chemical composition in relation to their weathering, nature of cementing material, hardness, texture, jointing, bedding planes