3 Rocks are solid pieces of the earth of any size Rocks are solid pieces of the earth of any size. They can be made up of one or more minerals, or they can be made up of solid organic matter.
4 3 Types by OriginIgneous – “from fire”; forms by cooling of magma or lavaSedimentary – formed from compaction and cementation of rock fragments (sediments)Metamorphic – “changed form”; from alteration of existing rock by heat, pressure and time
6 Igneous may become sedimentary, metamorphic, or igneous Sedimentary may become metamorphic, igneous, or sedimentaryMetamorphic may become igneous, sedimentary, or metamorphic
7 Rock PropertiesBowen’s Reaction Series – As magma cools, certain minerals tend to crystallize first. As they form out, they remove certain elements from the magma, which changes the composition of it. Thus different minerals form at different times during the cooling and solidification, and they generally always form in the same order.
8 The Canadian geologist N. L The Canadian geologist N.L. Bowen found that minerals tend to form in specific sequences in igneous rocks, and these sequences could be assembled into a composite sequence.
13 Magma is melted rock below the surface; liquid or fluid Melting depends uponTemperaturePressurePresence of fluidsMelt temperature depends upon the chemical composition of the rockPressure heightens melting point; release lowersFluids decrease some melting points
14 Partial Melting Different components have different melting points As each melts, magma composition of the magma is alteredOpposite effect of Bowens Series
15 Fractional Crystallization Opposite of partial meltingMinerals crystallize and change makeup of magma chemicallyIn same order as Bowens SeriesLonger formation time = larger crystalsShorter time = smaller crystalsInner/outer crystals may be different due to differences in the magma as time goes by
16 Igneous Rock TexturesCoarse grained – slow loss of heat by subsurface magma results in large, well-developed crystals (rough granite)
17 Igneous Rock TexturesFine grained – rapid heat loss from superficial lava results in small, poorly developed crystals (smooth basalt)
18 Igneous Rock TexturesPorphyritic – magma cools somewhat slowly, then speeds up near or on surface resulting in a mixed appearance/texture
19 Igneous Rock TexturesGlassy – viscous magma cools quickly with few dissolved gases forming few, if any crystalsObsidian
20 Igneous Rock TexturesVesicular - viscous magma cools quickly with a lot of dissolved gases forming few, if any crystals, but many bubbles (vesicles)Pumice
21 Igneous Rock Composition Felsic – lots of silica; light color; has minerals feldspar, mica and quartz; e.g., granite, rhyolite, obsidian, pumiceMafic – rich in Fe and Mg; dark color; minerals pl feldspar, pyroxene, ferromagnesians (hornblende); e.g., basalt and gabbroIntermediate – intermediate silica content;plagioclase, hornblende,pyroxene, and biotite; e.g., diorite and andesite
22 Igneous Rock Composition Felsic – lots of feldspar (fel); lots of silica (sic)Mafic – rich in Fe (f) and Mg (Ma) or ferromagnesiansIntermediate – intermediate blend
25 Some uses of Igneous rock: GRANITE: An igneous-plutonic rock, medium to coarse-grained that is high in silica, potassium, sodium and quartz but low in calcium, iron and magnesium. It is widely used for architectural construction, ornamental stone and monuments.PUMICE: An igneous-volcanic rock, it is a porous, brittle variety of rhyolite and is light enough to float. It is formed when magma of granite composition erupts at the earth’s surface or intrudes the crust at shallow depths. It is used as an abrasive material in hand soaps, emery boards, etc.GABBRO: An igneous-plutonic rock, generally massive, but may exhibit a layered structure produced by successive layers of different mineral composition. It is widely used as crushed stone for concrete aggregate, road metal, railroad ballast, etc. Smaller quantities are cut and polished for dimension stone (called black granite).BASALT: An igneous volcanic rock, dark gray to black, it is the volcanic equivalent of plutonic gabbro and is rich in ferromagnesian minerals. Basalt can be used in aggregate.
36 Clastic Imported fragments that are lithified By fragment size Conglomerate (breccia) – large fragments cemented by smallSandstone – quartz fragments (sand)Shale – clay sized fragments usually compacted into flat layers
38 Characteristics of Clastic Sediments Sorting – tendency of currents to separate sediments according to sizeAngularity – collisions during movement of particles tends to round them off. Little movement = angular; more movement = more rounded/smooth; great movement = most rounded/smooth particles
48 Sedimentary rocks have great economic importance - Oil, natural gas, coal, and uranium, our major energy resources, are formed in and come from sedimentary rocks.Sand and gravel for construction come from sediment.Sandstone and limestone are used for building stone.Rock gypsum is used to make plaster.Limestone is used to make cement.Salt is used for flavoring.Phosphate-bearing sedimentary rocks are used for fertilizer.Quartz sand is used to make glass.
51 MetamorphismThe process by which heat, pressure, or chemical processes change one type of rock into anotherChange into other mineralsChange in size or shapeSeparate into bandsChange mineral/chemical composition by addition/subtraction of materialsMost deep within the crustContact with hot magmaRegional from heat/pressure of tectonic forces
55 Metamorphic Classification FoliatedExtreme pressure causes crystals to realign or regrow in parallel bandsMinerals of different compositions separate to produce a series of bandsNon-foliatedNo bandingOriginal rock has basically one mineral so no separation or bandingOriginal rock has round/square grains that cannot realign when subjected to further stress
56 A rock that contains parallel- or sub-parallel-oriented mineral grains is said to be foliated Foliation promotes cleavage in rocks (they break easily along parallel planes).
57 If mineral crystals are disc or pencil shaped, their parallel orientation is easily discernible and the rock is clearly foliated. If all mineral crystals are equant (length, width, and height are equal) there can be no discernible parallel orientation.Nonfoliated rocks - mineral crystals are equant in shape.Made of calcite = marble (metamorphosed limestone)Made of quartz = quartzite (metamorphosed sandstone)
58 Uses for metamorphic rocks - Slate is used to make roofing tiles and in earlier periods of our history was used as "blackboards" in classrooms. As a resource, slate is nonrenewable, but common. Man-made roofing tiles are a suitable substitute.Marble is used as a building stone and as ornamental rock, such as for carving statues. As a resource, marble is nonrenewable, but common. Man-made building stones are a suitable substitute.
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