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Geology Exam 2
| Term | Definition |
|---|---|
| Weathering | Fragmentation and chemical decomposition of rocks 1: physical(mechanical) 2: Chemical |
| Regolith | Weathered rocks, mineral fragments and soil that blankets most of earths surface - "dirt" |
| Saprolite | "Rotten rock" Clay-rich regolith formed from intense in-place chemical weathering of bedrock |
| Soil | Combination of mineral grains, organic matter, water and air, that supports plant growth |
| Land Surface - pressure | Rock body forms deep in earth |
| Land Surface- expansion | Exposed by erosion, overburden removed |
| Chemical Weathering | Chemical decomposition of minerals into other minerals or non-mineral substances |
| Chemical Weathering- Hydrolyisis | Most important weathering process- silicate minerals- minerals reacts with water |
| Chemical weathering- Oxidation | Combination of metal with oxygen |
| General disintegration | Solid feldspar altars to soft clay- rock falls apart |
| Spheroidal weathering | Rock attached by chemical weathering; coners weather away faster,angualr boulders become round |
| Mass wasting | Movement of rock, soil or regolith downhill under the direct influence of gravity |
| Slide | Solid Rock |
| Slump | Unconsolidated rock- slope made less steep |
| Flow | Material moves as a thick fluid -mudflow -debris flow -earthflow -lahar |
| Creep | Very slow moevement; caused by cyclic expansion and contraction of regolith -freezing and thawing -wetting and drying |
| Causes of mass wasting | Oversteeping or alteration of slopes -river erosion -vegetation loss -construction activities -road cuts |
| Triggers of mass wasting | Water and Earthquakes |
| Gros ventre slide | Sandstone layer underlain by shale, oversteepened slope |
| Running water | -Hydrolyic cycle -Distribution of earths water |
| River/Running water | -Sediment erosion -Sediment deposition -Floods/runoff -Cycle of stream erosion |
| Gradient | -Slope of stream channel -Controls velocity of water |
| Velocity | -Speed of current -Controls size of sediment particles water can carry |
| Discharge | -Volume of water flowing past a point in river doing given time interval -Measured in units of volume per unit time |
| Alluvium | -Detrital sediment deposited by running water -Sand, gravel, mud |
| Meandering Stream | -Stream that winds back and forth in broad, looping curves -typically located on broad floodplain |
| Floodplain | -Flat floor of a valley formed by river lateral erosion and repeated flooding -Built up with alluvium |
| Braided Stream | -Sediment-chocked stream made of many intersecting channels |
| Bedload | -Course particles dragged and bounced along the bottom of the stream channel -Typically sand/gravel but floods can move boulders |
| Suspended load | -Silt and clay carried suspended within the moving water -Suspended load accounts for most sediment transport |
| Dissolved load | Portion of a stream's total sediment load that is carried in solution |
| Sediment deposition | River delta, alluvial fan, stream channel, floodplains |
| River delta | Where a stream meets larger body of water- normally ocean -sediment is deposited -velocity slows near zero |
| Alluvial Fan | -delta on dry land -stream exists mountain valley & velocity decreases to zero |
| Stream channel | -braided stream sediment -point bars |
| Floodplains | (point bars) -backswamp deposition -natural levees: ridges of sediment at rivers edge |
| Stream valley/ landscapes | -lateral erosion produces wide, flat valleys -verticle erosion (incision) produces steep, narrow valleys |
| What controls vertical vs. lateral erosion? | -Steep gradient: fast water, vertical erosion -Flat gradient: slow water, meandering stream, lateral erosion& vertical accretion |
| Base Level | indirectly controls stream gradient |
| Gradient controlled by base level | -High above base level: much available energy, steep gradient, fast water -Near base level: little energy, flat gradient, slow water |
| Rejuvenation | uplift raises landscape from near base-level to high elevation |
| Floods | -Overflow of stream channel -more water enters channel than can be moved downstream by channel |
| Effects of watershed alterations | -certain alterations to watershed can increase the amount of speed of runoff -all of these reduce infiltration & allow more rapid runoff |
| Watershed alteration: Removal of vegetation | -fire -logging |
| Watershed alteration: Urbanization | -roads/ parking lots -buildings |
| Effects of runoff | -accelerated erosion -larger/ more frequent floods -water pollution |
| When rainfall lands on ground it can do 1 of 3 things | -runoff -evaporate -infiltrate (soak) into ground |
| Groundwater | -largest source of "easily accessible" fresh water -naturally purified by physical filtration & biochemistry |
| Storage & movement of ground water- earths crust is a giant groundwater storage reservoir | -Recharge: water flowing in (slow infiltration of rainfall-sinkholes) -Discharge: water flowing out (Streams, springs, wells) |
| Porosity | -Measure of open spaces within a material -Determines how much rock or regolith can hold |
| Permeability | -Ease with which a fluid can flow through a material -Determines how easily you can extract water from rock/regolith |
| Gaining stream | -gains water from the ground ("normal" case) -virtually all streams in West GA |
| Losing stream | -loses water into the ground (common in desert climates) -also common where bedrock is extremely permeable |
| Groundwater seepage | streams grain water days, weeks, months, years or even centuries |
| Aquifer | water-saturated geologic unit that can transmit significant amounts of water under normal hydraulic conditions (have enough water) |
| Confined aquifer | an aquifer overlain by low permeability strata; water stored under pressure -common in layered sedimentary rocks |
| Perched aquifer | a localized aquifer above the main water table |
| Confining later (aquitard) | low-permeability layer that acts as a barrier to groundwater flow- opposite of aquifer |
| Artesian well | a well in which water rises above the top |
| Flowing artesian well | -water flows freely from well onto land surface -natural pressure within aquifer forces water up and out the top |
| Glacier | Large, perennial mass of ice, formed on land due to the comparison and recrystallization of snow that creeps downhill or outwards due to stress of its own weight |
| Type of glacier: Continental glaciers (ice sheets) | -cover vast areas -greenland and antartica |
| type of glacier: Valley glacier | "river of ice" -confined to mountain valley -common in high mountains |
| Making of glacier ice: Fresh snow | light and fluffy |
| Making of glacier ice: Firn | (corn snow) -recrystalization snowflakes -dense, hard ice blobs |
| Making of glacier ice: Glacier ice | -compared, fused firn -much entrapped air, dust |
| Making of glacier ice: Ductile ice | -under pressure ice can bend and flow -glacier rides downhill on basal layer of ductile ice |
| glacial erosion | (valley glacier). - generally occupy streams, valley and widen them out -streams erode only downward; also outward |
| drift | sediment deposited by glacial ice or meltwater |
| till | material deposited directly by ice. -unsorted crud -unweathered -moraines(terminal, lateral, medial, and ground) |
| stratified drift | outwash -material deposited by glacier meltwater |
Created by:
mckennaramsdell
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