GEO 101 1st Edition Exam 2 Study Guide Geology 101 Test 2 Study Guide Terms Weathering Generation of detritus via rock disintegration Deposition Settling out of the transporting fluid Erosion Removal of sediment grains from rock Breccia Coarse Clastics Composed of Gravel Sized Clasts Comprised of angular fragments o Angularity indicates a lack of transport processing o Deposited relatively close to source Conglomerate Coarse Clastics Composed of Gravel Sized Clasts Comprised of rounded gravel o Indicates water transport Clasts bang together forcefully in flowing water Collisions round angular corners and edges of clasts o Conglomerates are deposited at a distance from the source Shale Fine Clastics Composed of silt and clay o Silt sized sediments are lithified to form siltstone o Clay sized particles form shale o Fine clastics are deposited in quieter waters Floodplains lagoons mudflats deltas deep water basins Organic rich shales are the source of petroleum Sedimentary Structures Features imparted to sediments at or near deposition o Layering o Surface features on layers o Arrangement of grains Help decipher conditions at or near time of deposition Sedimentary rocks are usually layered or stratified o Arranged in planar close to horizontal beds o Bedding is often laterally continuous for long distances o Beds are often similar in composition color and texture Bedding reflects changing conditions during deposition These can be changes in o Energy conditions and hence grain size o Disturbance by organisms Bedding may also reflect non deposition or erosion A series of beds are referred to as strata Formation Strata recognized on a regional scale Geologic maps display the distribution of formations o i e Coconino Formation Water flowing over loose sediment creates bedforms Bedforms are linked to flow velocity and sediment size o Ripples cm scale ridges and troughs indicate flow Asymmetric ripples Unidirectional flow Symmetric ripples Wave oscillation Ripples are commonly preserved in sedimentary rocks Sandstone Sandstone Clastic rock made of sand sized particles o Forms in many depositional settings o Quartz is by far the dominant mineral in sandstones o Sandstone varieties Arkose Contains abundant feldspar pink color Quartz sandstone Almost pure quartz Digenesis Change that occurs to make sediments into sedimentary rocks o Lithification o Sedimentation Stratification Layering The formation of layering in a sedimentary rock Depositional Environments What type o environment would you find coal Metamorphism Metamorphism Formed by increase in temperatures and or pressures from o Igneous rocks o Sedimentary rocks o Other metamorphic rocks Low to high grade Rocks remain solid Agents of Metamorphism 1 Heat o Recrystallization results in new stable minerals o 2 sources Heat from magma Geothermal gradient 2 Pressure and Stress o Increase with depth o Forces applied in all directions 3 Fluids o Water and other volatiles o Enhance migration of ions o Recrystallization of existing minerals o Where does the water come from Pore spaces of sedimentary rocks Fractures in igneous rocks Hydrated minerals 4 Parent Rock o Minerals determines degree to which change occurs Metamorphic Textures Texture Size shape and arrangement of mineral grains Foliation Planar arrangement of mineral grains o Parallel alignment of platy and or elongated minerals o Compositional banding Foliation forms by o Rotation of platy and or elongated minerals o Recrystallization of minerals o Changing shape of grains into elongated shapes Types of foliated textures o Slaty Cleavage Planar surfaces along which rocks split Dullest o Schistosity Platy minerals exhibit layered structure Shiny o Gneissic Minerals segregate distinctively banded All of the dark crystals line up with each other and light crystals line up with each other and you see distinct bands Other metamorphic textures o Nonfoliated Minimal deformation Equidimensional crystals o Porphyroblasitc textures Large grains surrounded by fine grained matrix Metamorphic Rocks Foliated Rocks o Slate Fine grained Slaty cleavage Low grade metamorphism of shale o Phyllite Minerals not large enough to be identified Glossy sheen and wavy surfaces o Schist Medium to coarse grained Micas predominate Schistosity texture o Gneiss Medium to coarse grained Banded appearance High grade metamorphic Nonfoliated Rocks o Marble Coarse crystalline Calcite or dolomite o Quartzite Metamorphism of quartz rich sandstone Quartz grains interlocking 3 Types of Metamorphic Environments 1 Contact or thermal Metamorphism o Increase temperature from intruding magma o Zone of alteration aureole forms in rock surrounding magma 2 Hydrothermal Metamorphism o Chemical alteration caused when hot ion rich fluids circulate through cracks o Widespread along Mid Ocean Ridges 3 Regional or dynamothermal Metamorphism o Associated with mountain building Metamorphism and Plate Tectonics Continent Continent Collisions o Edges of plate deforms o Major mountains Alps Himalayas and Appalachians are metamorphic Subduction Zones o Linear belts of metamorphic rocks High pressure low temperature zones nearest to the trench High temperature low pressure zones further inland Slaty Cleavage Types of foliated textures o Slaty Cleavage Planar surfaces along which rocks split Dullest Schistosity Types of foliated textures o Schistosity Platy minerals exhibit layered structure Shiny Foliation Foliation Planar arrangement of mineral grains o Parallel alignment of platy and or elongated minerals o Compositional banding Foliation forms by o Rotation of platy and or elongated minerals o Recrystallization of minerals o Changing shape of grains into elongated shapes 4 Grades of Metamorphism Agents of Metamorphism 1 Heat o Recrystallization results in new stable minerals o 2 sources Heat from magma Geothermal gradient 2 Pressure and Stress o Increase with depth o Forces applied in all directions 3 Fluids o Water and other volatiles o Enhance migration of ions o Recrystallization of existing minerals o Where does the water come from Pore spaces of sedimentary rocks Fractures in igneous rocks Hydrated minerals 4 Parent Rock o Minerals determines degree to which change occurs Pyroclastic Debris Extruded Materials Pyroclastic Materials Fire Fragments Volcanic Bombs Bomb 64mm o Shaped kind of like footballs o Where there is a lot of pyroclastic degree o Coming out of cinder cone volcano pyroclastic degree only out of cinder cone o Largest