Igneous rocks form when magma cools and crystallizes either underground or at the surface. Sedimentary rocks form through the lithification of sediments. Metamorphic rocks form from pre-existing rocks undergoing changes due to heat, pressure, and chemically active fluids in the Earth's crust. The rock cycle illustrates how igneous, sedimentary, and metamorphic rocks are interrelated as they form and change over time through geological processes within the Earth.
8. composed of ions that move about freely.Crystallizationrandom movements of the ions slow, and the ions begin to arrange themselves into orderly patterns.cooling strongly influences crystal size.
10. quick cooling results the formation of solid mass of small intergrown crystals.Classifying Igneous RocksIgneous Textures describes the overall appearance of n igneous rock based on the size, shape, and arrangement of its interlocking crystals.Coarse-grained Texture - appearance of a mass of intergrown crystals, which are roughly equal in size and large enough to be identified with the unaided eye.
15. minerals that form at about the same temperature are found together in the same igneous rock.Naming Igneous RocksIgneous rocks are classified by their texture and mineral composition.Granitic Rocks – composed almost entirely of light-colored silicates – quartz and feldspar.
17. slabs of polished granite are commonly used for tombstones, monuments, and as building stones.Rhyoliteextrusive equivalent of granite and is composed essentially of the light-colored silicates.
18. rhyolite deposits are less common and generally less voluminous.Rhyolite Rocks
20. because of their iron content, basaltic rocks are typically darker and denser than granitic rocks.Basalt- a very dark green to black fine-grained volcanic rock.
21. Andesitic or Intermediate Composition- rocks with a composition between granitic and basiltic rocks.
24. Sediments are loose, unconsolidated accumulations of mineral rock particles that have been transported by wind, water, ice, or gravity and redeposited.Derived from the Latin sedimentum means settling, reference to a solid material settling out of a fluid.
25. Formation: weathering of pre-existing rocks 0 either by physical breakup into finer and finer fragments, or by solution.
27. usually, the particle are broken down further during this transport phase.
28. sediment become lithified, or turned to rock.Clastic Sedimentary Rocksfrom the Greek word klatos, meaning ‘broken’
29. formed from the products of the mechanical breakup of other rocks.
30. broken up into smaller and smaller pieces and ultimately, into individual mineral grains.Economic Importance of Sedimentary Rocks presently the source of over half the electronic power in the United States.
31. other major energy sources (petroleum and natural gas) occur in pores of sedimentary rocks.
32. other sedimentary rocks are major sources of iron, aluminum, manganese, fertilizer, and sand and gravel.
34. the rock is called conglomerate if the sediment is rounded.
35. the rock is called breccia if the pieces are angular.Sandstoneis the name given to rocks when sand-grains prevail.Shale is made of very fine-grained sediment.Siltstone is sometimes difficult to differentiate from rocks such as shale which is composed of even smaller clay-sized sediment.
37. does not remain dissolved in water indefinitely.Limestone – the most abundant chemical sedimentary rock.Coquina – a coarse rock composed of loosely cemented shells and shell fragments.
38. Chalk– soft, porous rock made up almost entirely of the hard parts of microscopic organisms.Travertine – type of limestone that decorates taverns.
40. the end product of the burial of large amounts of plant material over extended periodsWe divide sedimentary rocks into two major groups: detrital and chemical.The main criterion for classifying rocks are distinguished by their mineral composition.
41. Lithification of Sediment refers to the processes by which sediments are transformed into solid sedimentary rocks.Cementation – another important means by which sediments are converted to sedimentary rock.
46. produced from preexisting igneous, sedimentary, or from other metamorphic rocks.
47. every metamorphic rock has a parent rock – the rock from which it was formed.Metamorphism= to change form takes place where existing rock is subjected to temperatures unlike those in which it formed.
48. most changes occur at the elevated temperatures and pressures that exist in the zone beginning a few kilometers below Earth’s surface and extending into the upper mantle.Most metamorphismoccurs in two things:Thermal Metamorphism– when intruded by a magma body, change is driven by a rise in temperature within the host rock surrounding a molten igneous body.Regional Metamorphism – during mountain building, great quantities of rock are subjected to directed pressures and high temperatures and associated with large-scale deformation.
50. Heat as a Metamorphic AgentHeat is the most important agent of metamorphism.
51. it provides energy to drive chemical reactions that result in the recrystallization of existing minerals and/or the formation of new minerals.Two Sources of HeatRocks experience a rise in temperature when they are intruded by magma rising from below or contact metamorphism.Rocks that formed at Earth’s surface experience a gradual increase in temperature as they are transported to greater depths.
52. Pressure (Stress) as a Metamorphic Contentlike temperature, also increases with depth as the thickness of the overlying rock increases.
53. the deeper you go in the ocean, the greater you confining pressure.
54. the for the rock that is buried.Differential Stress – forces that generate mountains are unequal in different directions.- differential stress acts mainly as along the plane.
56. believed to play an important role in some types of metamorphism.
57. hot fluids aid in the recrystallization of mineral grains by dissolving material from regions of high stress then precipitating this material in areas of low stress.Metamorphic TexturesRock Slate – forms when shale is subjected to temperatures and pressures only slightly greater than those associated with the compaction that lithifies sediment.
59. Foliated Rocks – reorientation of the mineral grains into layered or banded appearance.Slate is a very fine-grained foliated rock composed of minute flakes.
60. a most useful rock for roof and floor tile, chalkboards, and billiard tables.
61. can be almost of any color, depending on its mineral constituents.
63. Schists– strongly foliated rocks, formed by regional metamorphism.- Platy and can be readily split into thin flakes or slabs.
64. Nonfoliated RocksMarble – a coarse, crystalline rock whose parent rock is limestone.- Composed of large interlocking calcite crystals, which formed from crystallization of smaller grains in the parent rock.
65. Quartzite – a very hard metamorphic rock most often formed from quartz and sandstone.
66. Rock Cycle allows us to view many of the interrelationships among different parts of the earth.
67. Helps to understand the origin of igneous, sedimentary, and metamorphic rocks.
68. See that each type is linked to the others by the processes that act within the planet.The Basic Cycle