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Earth Science Fall 2013.  Batholith- intrusive formation with at least a surface exposure of 100 square kilometers and reaching a depth of thousands.

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Presentation on theme: "Earth Science Fall 2013.  Batholith- intrusive formation with at least a surface exposure of 100 square kilometers and reaching a depth of thousands."— Presentation transcript:

1 Earth Science Fall 2013

2  Batholith- intrusive formation with at least a surface exposure of 100 square kilometers and reaching a depth of thousands of meters

3  Breccia- elastic sedimentary rock composed of angular fragments

4  Cementation- process in which dissolved minerals left by water passing through sediments bind sediments together

5  Chemical sedimentary rock- rock formed from minerals that precipitate out of water

6  Clastic sedimentary rock- rock made up of fragments from pre-existing rocks

7  Compaction- process in which air and water are squeezed out of sediments, resulting in the formation of sedimentary rock

8  Concretion- nodule of rock with a different composition from that of the main rock body

9  Conglomerate- sedimentary rock composed of rounded gravel or pebbles cemented together by minerals

10  Contact metamorphism- change in the structure and mineral composition of rock surrounding an igneous intrusion

11  Dike- igneous intrusion that cuts across rock layers

12  Evaporites- sedimentary rocks formed from minerals left after water evaporates

13  Extrusive igneous rock- rock formed from molten lava that hardens on the earth’s surface

14  Foliated- describing metamorphic rock with parallel bands

15  Fossil- trace or remains of a plant or an animal in sedimentary rock

16  Igneous rocks- rock formed from cooled and hardened magma

17  Intrusive igneous rock- rocks formed from the cooling of magma beneath the earth’s surface

18  Laccolith- flat-bottomed intrusion that pushes overlying rock layers into an arc

19  Lava Plateau- raised flat-topped area made of layers of hardened lava

20  Metamorphic rock- rock formed from other rocks as a result of intense heat, pressure, and chemical processes

21  Metamorphism- changing of one type of rock to another by heat, pressure, and chemical processes

22  Nonfoliated- describing a metamorphic rock without parallel bands

23  Organic sedimentary rock- rock formed from the remains of organisms

24  Porphyritic- describing an igneous rock composed of both large and small crystals

25  Regional metamorphism- metamorphism that affects rocks over large areas during period of tectonic activity

26  Rock cycle- series of processes in which rock changes from one type to another

27  Sediment- fragments that result from the breaking of rocks, minerals, and organic matter

28  Sedimentary rock- rock formed from hardened deposits of sediment

29  Sill- sheet of hardened magma that forms between and parallel to layers of rock

30  Stock- igneous intrusion with an area less than 100 square kilometers

31  Stratification- layering of sedimentary rock

32  Volcanic neck- solidified central vent of a volcano

33  Magma from the earth’s interior is the parent material for all rocks  From the time magma cools & hardens at or near the surface of the earth, the resulting rock begins to change.  Geologists have classified rocks into 3 major types based on the way the rocks are formed.

34  3 major rock types  Igneous rock  Sedimentary rock  Metamorphic rock


36  2 groups of igneous rocks that are classified according to where molten rock cools and hardens  Intrusive igneous rocks  Magma cools below the crust  Extrusive igneous rocks  Rapid cooling of lava on the earths surface

37  Extrusive & intrusive igneous rocks differ mainly in their sized of crystalline grain and is known as texture  Texture is determine by the cooling rate of the magma or lava that formed the rock

38  Slow loss of heat allows minerals to form large, well-developed crystalline grains  Coarse-grained texture  Ex: granite  Rapid loss of heat does not allow time for large crystalline grains to form, this produces fine-grained rock  Ex: basalt  Oceanic crust is made mostly of basalt

39  Lava or magma cools slowly at first & then rapidly as it near the earth’s surface, relatively large crystals embedded within a mass of smaller ones  Porphyritic  Highly viscous, silica-rich magma cools rapidly and no crystals form  Ex: obsidian

40  Magma that contains large amounts of dissolved gases hardens, the gases become trapped in the rock and produces rock full of holes  Ex: pumice

41  Determined by the chemical composition of the magma from which the rock develops  Divided into 3 families  Felsic  Intermediate  Mafic

42  Felsic rocks  Formed from magmas that are high in silica  Have light coloring of their main mineral components, orthoclase feldspar & quartz  May also contain plagioclase feldspar, biotite mica, & muscovite mica  Ex: granite, rhyolite, obsidian  Obsidian may be black, blue, or red depending on its chemical composition

43  Mafic rocks  Form from magmas that are low in silica but rich in iron and magnesium  Also can include ferromagnesian minerals making them dark in color  Ex: basalt, gabbro

44  Intermediate Rocks  Medium colored  Contain minerals such as plagioclase feldspar, hornblende, pyroxene minerals, biotite mica  Contain less quartz than the felsic family  Ex: diorite, andesite

45  Intrusions  Largest of all intrusions are batholiths  Form cores of several major mountain ranges like the Sierra Nevada range in CA & the Coast Range in BC  A stock is similar to a batholith only much smaller  Laccoliths form when magma flows between rock layers and spread upward sometimes pushing the overlying rock into an arc  Frequently found in groups  Ex: Black Hills

46  Sills form when a sheet of magma flows between layers of rock and hardens, it does not cause the arcing like a laccolith  Lie parallel to rock layers & vary in thickness from a few cm to hundreds of meters  Ex: Big Bend National Park in Texas  When magma forces its way through rock layers by following existing vertical fractures or by creating new ones and solidifies is called a dike  Common in areas of volcanic activity

47  Extrusions  A volcano is a cone of extrusive rock surrounding a central vent, when a volcano stops erupting for a long period the cone gradually wears away and the solidified central vent is left, this is called a volcanic neck  A lava plateau develops from lava that flows out of long cracks in the earth’s surface

48  Sedimentary rock is made up of accumulations of various types of sediments  Compaction & cementation are 2 processes that form sedimentary rocks  Sedimentary rocks are classified according to the kind & size of sediments that form them

49  Clastic sedimentary rock is made up of rock fragments carried away from their source by water, wind, or ice & left as deposits elsewhere  Chemical sedimentary rock forms from minerals that precipitate from water  Organic sedimentary rock forms from the remains of organisms

50  Classified by the size of the sediments they contain  Conglomerate- rock composed of rounded gravel sized fragments or pebbles  Breccia- rock made of rock fragments that are angular & have sharp corners  In both conglomerate and breccia the fragments can be easily viewed

51  Sandstones- rocks that are made up of sand sized grains that have been cemented together  Quartz is the major component  Many have pores between the sand grains through which liquids can move  Shale- rock that consists of clay-sized particles cemented and compacted under pressure  Usually pressed into flat layers that will easily split apart

52  Form from dissolved minerals that were once dissolved in water  Evaporites- rocks formed from the dissolved minerals left behind from water evaporating  Ex: gypsum & halite  Bonneville Salt Flats, Utah

53  Rocks formed from the remains of living things  Ex: coal & some limestones  Coal forms from decayed plant remains that are buried and compacted into matter that is mostly carbon  Organic limestones- from marine animal shells  Chalk- made up of tiny, one-celled marine organisms  Originally forms as mud on the ocean floor  Ex: white cliffs of Dover, England

54  Stratification  Layering of sedimentary rock that occurs when there is a change in the kind of sediment being deposited  Type of deposit varies for many reasons  Layers vary in thickness  Grade bedding- occurs when various sizes and kinds of materials are deposited within one layer

55  Ripple Marks & Mud Cracks  Ripple marks are formed by the action of wind or water on sand  Mud cracks result when muddy deposits dry and shrink; the shrinking causes the dried mud to crack

56  Fossils  Remains or traces of ancient plants and animals  Usually preserved in sedimentary rock  Concretions  Lumps of rock with a different composition from the main rock body  Form when minerals precipitated from solutions build up around an existing rock particle  Groundwater sometimes deposits dissolved quartz or calcite inside cavities of sedimentary rock where it crystallizes and forms a geode.

57  Metamorphism is the changing of one type of rock to another by heat, pressure, and chemical process  Most forms deep beneath the surface of the Earth  All is formed from existing igneous, sedimentary, or metamorphic rock

58  During metamorphism certain minerals change into other minerals; some minerals change in size or shape or separate into parallel bands that give the rock a layered appearance

59  2 types of metamorphism occur in the earth’s crust  Contact metamorphism occurs when rocks come into direct contact with or very near magma  Regional metamorphism occurs due to heat and pressure created by tectonic activity  Most metamorphic rock is formed by regional metamorphism, however rocks formed by contact metamorphism can also be found where regional metamorphism has occurred.

60  Classified according to their texture into two categories  Foliated- have parallel bands of minerals  Non-foliated- do not have parallel bands of minerals

61  Foliated Rocks  Form in 2 ways  Extreme pressure may flatten the mineral crystals in the original rock & push them into parallel bands  Minerals of different densities separate into bands, producing a series of alternating dark and light  Ex: slate, schist, gneiss  Slate- formed by pressure acting on shale  Schist- formed when a greater amount of heat & pressure change slate into a coarser-grained rock  Gneiss- greatly metamorphosed rock with bands of light and dark minerals

62  Do not have bands of crystals  Quartzite- forms when sandstone undergoes metamorphosis  Heat & pressure cause the mineral grains to recrystallize so that the spaces between them disappear  Marble- formed from the compression of limestone

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