GEOL 101 1nd Edition Exam 2 Study Guide Lectures 11 18 Lecture 11 What are Earth s external processes that happen on the surface Erosion Physical removal of material by water wind and ice Weathering Physical breakdown and chemical alteration of rocks Mass Wasting Transfer of rock soil down a slope due to gravity What types of mechanical weathering is that Frost wedge water seeps into cracks and breaks rock exfoliated overlying rocks are exposed and pressure is reduced biological activity plants and animals Lecture 12 What are the three major processes of chemical weathering Dissolution some minerals are easy to dissolve in acidic water rain water with CO2 in the air to form carbonic acid As rock dissolves small voids are formed and eventually get larger to form caves best example would be Limestone and marble which are both made of calcite Oxidation rust any chemical reaction where a compound loses electrons to oxygen This is important in decomposing mafic minerals they have high iron Hydrolysis Reaction of any substances or rocks with water Hydrogen ions attack and replaces positive ions What controls rates of weathering Climate temperature and moisture rock characteristics calcites and silicates and differential weathering igneous metamorphic and sedimentary rocks What are the factors controlling soil Parent Material the source of the weathered material from which soil forms Residual underlying bedrock Transported carried from somewhere else and deposited Time Affects amount of weathering and the thickness longer it forms thicker it is Climate Affects kind of weathering which affects the kind of soil that forms Plants and Animals Important to add nutrients to the soil when they decompose Slope Steep slopes have poorly developed soils What are the factors to stabilize slope Water content and vegetation Lecture 13 What are some mass movements Falls are the fastest form or mass wasting Materials free falls or rolls down a steep slope or cliff Slides occur when material moves down along a sloped surface Can be very fast and catastrophic or very slow Flows occur when unconsolidated slope material becomes water saturated Can include soil vegetation or rock sediments Creeps is a very slow type of Earth flow moving as slow as 1 mm per year Can be triggered by freeze thaw water freezes and expands and creep their way downslope What are some land failures Weather Heavy precipitation or snowmelt can trigger mudflows debris flows and lahars Earthquakes Can shake loose otherwise stable land Wildfires Consume vegetation leaving slopes more exposed to heavy precipitation and failure later on Slope Steeping This may be natural by rivers or ocean waves eroding the adjacent land Permafrost Subsidence Permafrost is permanently frozen ground in high altitudes and polar regions Heat from buildings leaks into subsurface can melt frozen ground water Withdrawing groundwater Houston s use of groundwater has caused parts of Galveston TX to sink below sea level Lecture 14 Sedimentary rocks are important because Rocks made up a small layer of the crust and provide information about the past environments provide information about transport contain fossil fuels contain petroleum coal and economic resources Name two processes of lithification Compact sediments accumulate and gets heavy enough to put pressure on the bed underneath and cementation loose sediments glued together What are the two sources for sedimentary rocks Detrital rocks sediment as solid particles typically the result of mechanical weathering but they may be from chemical weathering too and Chemical rocks sediment that was once in solution What are the types of sedimentary environments Continental Environments Dominated by erosion and deposition associated with streams and colder regions are glacier erosion and Marine Environments Large quantities of continental sediments that have been washed down Other areas have warm carbonate rich waters ideal for coral reef communities What are some energy resources Coal potential environmental problems from mining and air pollution Acid mine draining from sulfide minerals pyrite Oil and natural gas derived from the remains of marine plants and animals Zooplankton and algae Oil trap geologic environment that allures significant amounts of oil and gas to accumulate Porous permeable reservoir rock often times a sandstone and impermeable cap rock such as shale Lecture 15 What is metamorphism Metamorphism is to change form by increased temperature and or increased pressure Produced from all three rocks in the Rock Cycle During metamorphism the rock must remain in solid form but once it begins to melt it returns back to igneous rocks What are some agents concerning metamorphic rocks Heat Provides the energy necessary for chemical reactions that change existing minerals into new minerals Two sources of heat Contact metamorphism heat from chamber and Pressure stress Chemically active fluids Mainly water with other volatile components Sources of fluids Pore spaces sediment Fractures igneous rocks Hydrated minerals like clay and mica Parent Rock original rock from which the metamorphic rock formed Most metamorphic rocks have the same overall chemical composition as the parent rock from which they formed What are the different types of textures Foliated planar arrangement of minerals nonfoliated nonplanar arrangement of minerals and porphyroblastic large crystals surrounding by small crystals Lecture 16 What is the different types of environments for metamorphic rocks 1 Contact or thermal Metamorphism occurs due to rise in temperature when magma invades a host rock and bakes it Most easily recognized when it occurs at the surface or in a nearsurface environment 2 Hydrothermal Metamorphism is closely associated with igneous activity which act as the heat source While magma cools ions that are not incorporated in to mineral crystals combine with left over volatiles water 3 Regional Metamorphism produces greatest quantity of metamorphic rock Associated with convergent tectonics and mountain building The crust is thickened burying rocks deeper and deeper which results in additional metamorphism 4 Burial Metamorphism associated with very thick sedimentary strata Required depth varies from one location to another depending on the geothermal gradient 5 Subduction Zone Metamorphism are sediments along an active margin get deformed The deformed segment is called an accretionary wedge 6 Metamorphism along Fault Zones