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Geology
Exam 1 Material
| Term | Definition |
|---|---|
| Geology | Application of the other natural sciences and mathematics to the study of earth processes and history |
| Environmental Geology | past and present geologic environments of earth's surface and near surface systems and how they function |
| Geology vs Other Natural Sciences | involves history and pre-history experiments/simulations are sometimes difficult/impossible due to physical/time scales, extreme conditions, complexity reverse engineering from limited remaining products relies heavily on observations |
| Supporting Evidence | Evidence that is consistent with the hypothesis but clearly insufficient to prove it |
| Conclusive Evidence | Evidence that proves the hypothesis |
| Negative Evidence | the absence of evidence is not the evidence of absence |
| Minerals | naturally occurring, inorganic, solids, specific composition, crystalline |
| Common Mineral Groups (cations and anions) - classified by anion | oxides, silicates, aluminosilicates, carbonates, sulfides, sulfates, chlorides |
| crystals/crystalline materials | arrangements of atoms in a chemical compound in a regularly repeated pattern or lattice structure |
| crystallization | atoms bond, more atoms added to already formed crystals (act as templates) 1. cooling of a hot liquid: magma (molten rock) -- also occurs as vapor adding to crystals (snowflakes) 2. precipitation from a saturated solution (salt solutions or brines) |
| when several different minerals crystallize from a magma or solution (multi-phase mixture) | diff minerals form at diff times (temps or solution concentrations) crystallization can overlap or form a sequence one crystal can form over a range of temperatures or concentrations |
| features formed during crystallization | zoned crystals (concentric growth bands) interlocking crystals |
| rock | naturally occurring solid composed of minerals/other solid materials may have non-crystalline and biological materials |
| igneous rock | formed by cooling of magma classified by: grain size (coarse/fine), general chemistry (color, darker=more iron, less silicon/aluminum) |
| sedimentary rock | formed from sediment or chemical and biological precipitates deposited at earth's surface |
| metamorphic rock | formed by alteration of existing rocks by later heat and pressure |
| glass | hardened substance that may be crystalline only at an atomic level - too small to see in optical microscopes sometimes called "non-crystalline" usually in lava flows and volcanic ash |
| lava | magma that has reached earth's surface |
| Slow cooling | Intrusive/Plutonic, coarse crystals easily visible, thousands of years+, in subsurface |
| Fast cooling | Extrusive/Volcanic, fine crystals not usually identifiable w/o magnification, days to few years, very near surface |
| quenching/very fast cooling | extrusive, non-crystalline glass, seconds to hours, |
| Types of Igneous rock | Granite: coarse Pegmatite: very coarse |
| intrusive rock units | dike, sill, pluton |
| extrusive rock units | lava flows and airborne material, volcanic ex. basaltic lava flow, obsidian |
| weathering | physical and chemical breakdown of rocks at earth's surface where conditions are different from where most rocks formed |
| surface conditions (weathering) | ATM temps and pressures available H2O, O2 acids (H+) |
| weathering results | smaller particles new minerals + cations and anions in solution soils = buildup of weathering by-products |
| erosion | removal of weathered material by transport processes can be particles or in solution |
| formation of sedimentary rocks | deposition of sediment and 1 or a combo of processes: compaction, dewatering, cementation |
| comapction | particles pushed closer together and pore spaces smaller under weight of more sediment |
| dewatering | some water is squeezed out |
| cementation | filling of pore spaces with chemical precipitates |
| bedding | layers or beds that pile up over time |
| clastic sedimentary rock | made of particles or grains (clasts) eroded from earlier rocks |
| non-clastic sedimentary rock | made of sediment that is either chemically or biologically precipitated or accumulated |
| conglomerate | rock containing larger than sand-sized particles |
| clastic sedimentary rock types | conglomerate (breccia - angular clasts) pebbly (sandstone/sandy conglomerate) sandstone siltstone shale (silt/clay mix - most common sedimentary rock type) claystone |
| non-interlocking texture (in sedimentary rocks) | touching and not enclosing each other |
| non-clastic sedimentary rock types | limestone (with fossils) - up to 20% of all sedimentary rocks rock salt (mostly halite) gypsum - from evaporating seawater coal - from highly compressed, devolatilized plant matter sedimentary chert (precipitated silica) |
| features in sedimentary rocks | bedding, sedimentary structures, fossils |
| annual layers/bedding | winter = darker, summer = lighter, clayey fine sand and silt |
| sedimentary structures | mudcracks - contraction when mud (with clay) dries wave/oscillatory ripples - waves moving across shallow water as tide recedes |
| metamorphism | folding and tilting shape change: mineral grains are soft and deform easily recrystallization: mineral grains reform w diff crystal orientation new minerals form: stable at higher temps/pressures baking: next to intrusions (high temp) melt --> magma |
| metamorphic banding | new formed minerals segregate into separate layers not bedding! |
| schist | metamorphic rock formed by high pressure/temp recrystallization w abundant visible mica - grown as flat planar grains, then folded/bent |
| gneiss | high-grade metamorphic rock formed at great depth mineral regrowth and segregation created banding |
| rock cycle | |
| unconformity | gap in record by either erosion or non-deposition at earth's surface represents significant missing time had a sedimentary unit or extrusive igneous unit laid upon it OR it is the modern eroded land surface |
| uniformitarianism | past events obeyed the laws of mathematics/physics/chem just like processes today |
| superposition | sediment is always deposited on some other sediment or rock that is older |
| horizontality | sediments are deposited almost always horizontally inclining, dipping, tilting occurred after deposition exceptions: crossbeds and mass movement deposits (landslides) |
| continuity | strata found truncated at earth's surface originally extended in all directions until thinning to nothing (or reached edges of their depositional basin) |
| intrusion | intrusive igneous rock must be younger than the rock it intrudes ex. dike: much younger, includes crosscutting |
| crosscutting | fault, erosion surface, or intrusive igneous rock unit is younger than the rock it cuts across ex. dikes, faults |
| inclusion and derivation | part of a rock unit is derived from another rock unit, it must be younger than the material of which it is composed older rock units encolosed in an igneous rock body parts of sedimentary rock derived from older rocks |
| hierarchy of time units (longest to shortest) | eons, eras, periods, epochs, stages (ages) |
| exogenic system | driven by energy outside the earth (includes some endogenic components, like geysers) |
| groundwater | water in the subsurface below the water table or the point where saturation starts occurs in small cracks and voids, non-static moving generally slowly, artesian refers to subsurface pressure conditions, primarily used for irrigation |
| potability of water | drinkable - depends on what's dissolved in it and other characteristics |
| circular irrigation | each its own well with a pipe rotating/spraying, inefficient (90% evaporates, leads to soil salinization) |
| small or micro-scale GW occurrence | voids: inter-granular pore spaces (cavities, between mineral grains) planes: cracks, fractures, bedding planes intersecting cracks/fractures/joints create a network for water flow |
| GW occurrence properties | porosity and permeability |
| porosity | decimal percent of rock or sediment by volume that is voids n = void Volume / total Volume |
| permeability (more important to groundwater!) | hydraulic conductivity (K) numerical expression of how easily water can pass through a material depends on water temp, diameter/width of voids, connectivity of voids |
| drainage basin or macro-scale GW occurrence | land surface Vadose Zone: Unsaturated, zone of aeration Phreatic Zone: Water table Phreatic Zone: Saturated, zone of saturation |
| Discharge | baseflow where water comes back out to the land surface |
| Recharge | |
| runoff vs infiltration factors | magnitude of precipitation event permeability of land surface (sediment, soil, rock type, structures) ground conditions (already saturated, frozen, cracks from drying) steepness of slope vegetation density/type climate land use |
| perennial vs intermittent baseflow factors | perennial (flow all the time) intermittent (during storms or seasonally) |
| where does water in the stream come from | baseflow, runoff, direct precipitation, tributaries |
| what makes groundwater move | things move from places of high energy to low energy (potential and kinetic) |
| Total Head | Elevation head (Z) plus pressure head (P) |
| piezometer | pipe or well installed into the ground open at the top to the atmosphere (1 atm), has no holes in its sides so water can only enter at the bottom, is open at the bottom to saturated conditions (groundwater) where water pressure is > 0 |
| head conditions in natural settings | H=Z+P |
| head conditions in a static body of water (lake) | H (total head) values are equal despite variety in Z and P values No Flow |
| head conditions in a hilltop (recharge area) | elevation and pressure heads vary total heads vary flow from high total head to lower total head downward flow |
| head conditions in a valley bottom (discharge area) | elevation and pressure heads vary total heads vary flow from high total head to lower total head upward flow |
| drainage basin (gw) divide | separates water that could drain to a particular basin vs others |
| head conditions at water table | pressure (P) = 0, total head (H) = elevation head (Z) |
| hydrogeologic unit | a geologic unit classified based on its hydraulic conductivity or permeability characteristics |
| aquifer | saturated unit or any part of one that easily transmits water high permeability where people put wells |
| aquitard | saturated unit or any part of one that does not easily transmit water low permeability |
| aquiclude | rare saturated unit that essentially transmits no water or is considered impermeable |
| unconfined aquifer (water table aquifer) | aquifer in which the upper surface of saturation (the top) is the water table (nothing covering) |
| confined aquifer | aquifer bounded above by an aquitard or aquiclude (a confining unit of low permeability) |
| artesian conditions | when water will rise in a piezometer above the top of the unit (above the water table in an unconfined aquifer and above the top surface of a confined aquifer where it is overlain by a unit of low permeability) |
| flowing artesian conditions | when water will rise in a piezometer above the land surface |
| potentriometric surface map | head values at top of an aquifer if unconfined, also a map of the elevation of the watertable |
| hydrogeologic cross section | head values at depth within an aquifer flow is generally perpendicular to head lines |
| Darcy's Law | Q= -KiA Q= -[K(Hf-Hi)A]/L Q= positive flow, K=coefficient proportional to permeability/hydraulic conductivity, i=(head final - head initial)/length of Hi to Hf, A=cross-sectional area of the water flow |
| cone of depression | drawdown from pumping of wells |
| intersecting cones | can lower the watertable in the area |
| dissloved solids (ions) | cations: Na, K, Mg, Ca, H anions: Cl, HCO3, CO3, SO4, OH common elements in the earth's crust coming in contact w the water |
| dissolved gases | CO2, O2, SO2, H2S, CH4, NH3 O2 and CO2 enter gw mostly from atmosphere Sulfur gases come from minerals that contain sulfur methane and ammonia often associated with organic activity/decay |
| electroneutrality | natural solutions have a charge balance analysis of a water sample should show electroneutrality |
| if water analysis does not show electroneutrality within a 5% analytical uncertainty | analysis is flawed due to technician or equipment error or there are ion(s) in solution not on the list above that have not been measured |
| iron (in water) | frequently seen in solution but in a very low concentration essentially insoluble except in solutions that are acidic and anoxic (low oxygen) |
| manganese (in water) | dissolved, behaves like iron but requires more oxygen to precipitate stains rock surfaces and sediment |
| lead (in water) | low natural concentration unless there are lead minerals in the local rocks usually from pipes and solder |
| arsenic (in water) | from pollution (insecticides) or a natural occurrence (metamorphic rocks) poisonous in drinking water very mobile, easily transported through soils into groundwater by infiltration and recharge |
| TDS (total dissolved solids) | a way of gauging the concentration of dissolved material or saltiness of a solution natural solutions near the land surface have relatively low TDS |
| potable water | drinkable water <700mg/l TDS value |
| source of TDS | enter groundwater as result of chemical reactions w rocks, minerals, and sediment, both at land surface in soils (chem weathering) and in the subsurface gw system as it travels through rocks and sediment |
| concentration of dissolved solids | increases from point of infiltration until it discharges determined by time and distance of transport in ground, types of rocks and minerals encountered, subsurface conditions (temp, press, pH, O2 content, etc) that influence chemical rxns |
| compositional layers of earth's interior | crust: continental (fairly light, mostly feldspar) and oceanic mantle: can be seen, thick layer like playdough core: never seen, but seen in meteorite materials |
| rheological/mechanical layers of earth's interior | lithosphere: crust and outer mantle, rigid and strong, rock asthenosphere: inner mantle to core, weak, soft deforms plastically or as viscous liquid |
| how we know about earth's interior | inclusions from great depth by basaltic magmas earth's overall mass indicates highly dense core magnetic field requires metallic liquid/conductive outer core surrounding solid inner core seismic waves interact with interior layers other planets |
| s-wave patterns (earthquake shock waves) | shear waves - can't go through core/liquid |
| p-wave patterns (earthquake shock waves) | compression waves - can go through liquid |
| convection | circulation in the asthenosphere, driving force in plate tectonics colder/denser material sinks warmer/less dense material rises |
| divergent plate boundaries | rift valley (cc and cc) or mid ocean ridge (oc and oc) moving away from each other |
| convergent plate boundaries (subduction zones) | highest frequency of earthquakes island arc system: very deep hole, melting into magma continental margin: OC always subducts beneath CC bc density moving toward each other |
| transform plate boundaries | mid ocean ridge (parts) strike-slip faults friction leads to snapping/breaking leads to earthquakes moves past each other |
| chemical weathering | breakdown of rocks and minerals at earth's surface by chemical reactions |
| mechanical (physical weathering) | breakdown of rocks and minerals at earth's surface by physical processes |
| karstification | dissolution or chemical decay of rock that produces landforms by rock removal in solution |
| karst | landforms produced by kartstification (caves, sinkholes, towers) dolomite and calcite rocks most commonly affected (CaCO3 and CaMg(CO3)2) -- limestone |
| carbonation of calcite (limestone) | puts calcite in solution calcite + water + CO2 --> calcite, water and carbon create carbonic acid --> calcite dissolutes, CO3 joins extra hydrogen to create bicarbonate ions weathers pretty rapidly, more CO2=faster decay |
| reverse carbonation | calcite precipitates calcium and bicarbonate create calcite and carbonic acid, carbonic acid reverts to water and carbon dioxide |
| acid sources (H+ supply) | carbonic acid (mostly plant decay in soils and atmosphere) sulfuric and hydrosulfuric acids (weathering of sulfide minerals and H2S gas associated w coal, natural gas, petroleum, and volcanism organic decay |
| surface karst | limestone rock surface features: holes, widened fractures sinkholes tower karst |
| cave development | carbonation dominates development of surface and subsurface karst features prexisting permeability, water w CO2 moves rapidly, enlarges paths and produces vadose (unsaturated zone) caves reacts with limestone, widening passageways |
| vadose caves | high to low elevation, above watertable |
| mixing 2 diff saturated solutions | undersaturated soil soln. with saturated gw at the water table can create an unsaturated soln. caves develop at and just below the water table phreatic (staturated zone) caves stream dissection, valley deepening, WT drops, caves dry/ventilated |
| formation of speleothems: dripstone | soil moisture drips into cave and loses CO2 to in cave causes over saturation dripstrone (stalactite and stalagmites pricipitates) tufa precipitates when oisture/gw seeps out of hillside and loses CO2 to air causing saturation |
| stalactites | dripstone deposit handing from ceiling |
| stalagmites | dripstone formed on floor of cave |
| column | when a stalactite joins a stalagmite |
| ribbons | formed as vertical sheets from sloping ceiling |
| soil | layer formed at earth's surface by the buildup of weathered materials form in place, by the alteration of existing geologic materials not deposited weathering>erosion involves chem and physical processes |
| surficial deposits | non-lithified (soft) materials at earth's surface laid down by geological processes of transport and deposition may be weathered but not produced by weathering |
| dissolution | minerals dissolve into component ions in solution only important to a few uncommon minerals |
| hydrolysis and acid hydrolysis | minerals react with water alone and water with hydrogen ions acid hydrolysis dominates in natural systems (faster) |
| hydration and dehydration | minerals attach or release water from chemical bonds, especially clay minerals dehydrate = shrink hydrate = expand mineral + water = new minerals |
| oxidation and reduction | metals have their valence state raised (lose electrons) by combining with oxygen reduction is the reverse |
| effects of chemical weathering | color/composition changes - change to clay minerals/oxides weathering rinds - outer discolored layer due to chem weather changes, thicker with time pebble ghosts - stones have had a constituent (often calcite) removed by chem weather --> lower density |
| impact and abrasion | particle contact with other particle or rock surfaces glacial striation and streamlining |
| wetting and drying | water absorption and desiccation can cause expansion and contraction |
| freeze-thaw | repeated freezing, melting, and refreezing of water requires pre-existing fractures |
| crystal growth (other than ice) | precipitation of solid compounds, usually salts or calcite salt crystals put more force on rock fractures than frozen water |
| heating and cooling (insolation weathering) | high temp heating and sudden cooling causes rocks to break at their surfaces along curved fractures |
| exfoliation | peeling of surface parallel or concentric layers (any scale) causes: release pressure near surface expansion, chem weather of surface minerals, freezing of moisture that has seeped inward, surface expansion, hydration/drying of near surface clay minerals |
| grus/grusification | granular, grain by grain, disintegration of coarse-grained igenous rock causes: freeze-thaw, light chemical weathering, water absorption that causes expansion |
| weathering rates in common minerals | quartz: hardest common mineral, chemically resistant feldspar: most common mineral, mid hardness/chem resistance calcite: softer than other minerals, low hardness/chem resist how well it's cemented affects rate of weathering |
| differential weathering | different rates of weathering for adjacent rocks and structures, either different rock types or preferred weathering along bedding planes and fractures |
| arid climate weathering | mechanical weathering dominates, slow total weathering |
| humid climate weathering | chemical weathering dominates, total weathering relatively fast both chemical and mechanical weathering are faster |
| O-horizon | >90% decaying organic matter dark brown/black color may be absent in arid regions w sparse vegetation may be thick cooler climates w abundant moisture in soils (slows decay) |
| A-horizon | zone of leaching = stripping of cations by dissolution/chemical rxns, most heavily weathered horizon mostly mineral material albic horizon = special type of A horizon with very light color from extreme leaching |
| B-horizon | zone of accumulation red/yellow color enrichment in clay minerals, oxides by chem precipitation, translocation and insitu weathering translocation = accumulation of solid by product weathering that filter down from horizon above |
| C-horizon | lightly altered parent material, but disaggregated parent material can be still be recognized although partly altered |
| factors in soil development: control type, thickness, and degree of weathering | parent material - composition, grain size, permeability climate - avail moisture / temp vegetation - soil acidity, moisture retention, erosion topography - steepness (drainage/runoff potential), orientation of slopes time - maturity of soil |
| non-linear soil growth over time | thickness of solum increases, land surface lowers bc some ions are removed by chemical weathering, rate of penetration slows down, thickness stays same once land surface is lowering at same rate as penetrating subsurface |
| soil in humid temperate climates | clay and fe-oxide hydroxide enrichment in B horizon B-horizon has yellow-orange color CaCO3 leached from B horizon silica(quartz) easily preserved |
| soil in humid tropical climates | never glaciated = very deep, highly weathered, never cleared aluminum and Fe-oxide/hydroxide enrichment in B horizon B-horizon usually intense red or pink color silica (quartz) leached or badly decayed - soluble gel, concrete-like once dried |
| soils in hot arid climates | salt and calcite precipitates in B horizon and can form a natural cemented horizon organic material very sparse, no O horizon often wind derived mineral grains are added to soil as it forms |
| soils in temperate to cool humid and arctic climates | soils vegetation covered, retain moisture and may be saturated organic material does not decay as fast as it accumulates, build up of peat or turf horizon very thick O horizon that may dominate profile A horizons are heavily leached by acids |
| paleosols - ancient soils | formed under past conditions, rock conditions with soils trapped in them buried paleosol - soil buried by accumulating sediment or volcanic deposits relict paleosol - soil formed in past but still at modern land surface, no longer forming and could not |
| loess | wind deposited silt |
| mass movement | erosion and transport of material downslope under the influence of gravity without primary transport by a fluid |
| when a failure occurs | shear stress (applied force) > shear strength (resistance ability of material) |
| factors of mass movement | slope (doesn't have to be very steep) fluids involved - adds weight (stress), decreases strength of material, can develop pressure type of material - sediment (clay?), rock, structures (fractures) |
| types of mass movement | fall slide flow slump/rotational slide creep classification parameters: coherent (single block) vs non-coherent (mixes while moving), speed (100m/s to <1cm/yr) |
| fall | vertical movement, toppling or tumbling lots of momentum |
| slide | rapid, coherent (slab-like) movement on a well-defined slip plane can break up toward end (starts as single mass) surface level |
| flow | non-coherent movement of saturated sediment comes in surges, almost always saturated with a fluid (can be air) rapid or slow ground saturated upflow |
| slump or rotational slide | most common at top: slide on a curved surface, coherent at bottom: toe exhibits non-coherent movement sediment moves up out of subsurface |
| creep | very slow, non-coherent movement of soil debris and sediment expansion and contraction leading to creep: wetting and drying, freeze-thaw |
| mass movement triggering mechanisms | earthquakes - shock waves increase stress volcanic activity - abundant loose material heavy precipitation - saturated ground is weaker and heavier post fire events - removal of plants that protected soil fractures and bedding planes are weak |
| permafrost | permanently frozen ground doesn't allow infiltration to occur upper part of land surface that thaws in summer is organic rich and becomes saturated and weak |
| mass movement deposits (descriptive terms) | poorly sorted, mixture of many grain sizes poorly defined bedding - not deposited grain by grain breccia - conglomerate with angular particles muddy conglomerate |
| mass movement deposits (genetic terms) | colluvium - any deposit created by mass movement collapse breccia - formed by collapse of a cave ceiling talus - type of colluvium, angular rock debris with no fine particle sitting at the angle of repose at the base of a cliff that has rockfalls |
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briannaarce
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