GEOL 101 1nd EditionExam #2 Study Guide Lectures: 11 - 18Lecture 11 What are Earth’s external processes that happen on the surface?Erosion: Physical removal of material by water, wind, and iceWeathering: Physical breakdown and chemical alteration of rocksMass Wasting: Transfer of rock soil down a slope due to gravityWhat types of mechanical weathering is that?Frost wedge (water seeps into cracks and breaks rock), “exfoliated” (overlying rocks are exposedand 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 calciteOxidation (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 ionsWhat 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 formsPlants and Animals—Important to add nutrients to the soil when they decomposeSlope—Steep slopes have poorly developed soilsWhat are the factors to stabilize slope?Water content and vegetationLecture 13What are some mass movements?Falls—are the fastest form or mass wasting. Materials free falls or rolls down a steep slope or cliffSlides—occur when material moves down along a sloped surface. Can be very fast and catastrophic or very slowFlows—occur when unconsolidated slope material becomes water saturated. Can include soil, vegetation, or rock sedimentsCreeps—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 downslopeWhat are some land failures?Weather-Heavy precipitation or snowmelt can trigger mudflows, debris flows, and laharsEarthquakes-Can shake loose otherwise stable landWildfires-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 landPermafrost Subsidence-Permafrost is permanently frozen ground in high altitudes and polar regions. Heat from buildings leaks into subsurface can melt frozen ground waterWithdrawing groundwater-Houston’s use of groundwater has caused parts of Galveston, TX to sink below sea level Lecture 14Sedimentary 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 algaeOil 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 15What 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 formedWhat 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 16What 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 near-surface 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 metamorphism4) Burial Metamorphism associated with very thick sedimentary strata. Required depth varies from one location to another depending on the geothermal gradient5)