EXAM 2 Study Guide - John Madsen PDF

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GEOL 107 - GEOLOGY OF DYNAMIC EARTH - STUDY GUIDE PART 2 https://quizlet.com/28809655/ud-geol-107-exam-2-flash-cards/ https://quizlet.com/237629978/geol-107-exam-2-study-guide-madsen-flash-cards/ This guide contains in an outline/question format the important points that we have covered in the course, you will be expected to have an understanding of this material for an exam Hydrologic Cycle and River Systems - Chapter 10 in Physical Geology Know the relative distribution of water on the Earth Oceans – 96.50% Glacial Ice – 1.76% Groundwater – 1.70% Lakes and Rivers - 0.014% Soil Moisture – 0.001% Atmosphere - 0.001% Understand the hydrologic cycle What are the main parts of the cycle? e.g., evaporation, precipitation, runoff, groundwater, and transpiration. What are the excesses in evaporation vs. precipitation for the oceans and for land? What balances these excesses? ● Evaporation: water changing from liquid to gas (water vapor) driven by heat from sun ● Condensation: water changing from gas to liquid- driven by water vapor moving up in earth’s lowermost atmospheric layer (troposphere) and being cooled ● Precipitation: condensed water vapor in troposphere falling back to earth’s surface as rain, snow ● Surface runoff-water flowing on land surface downhill to oceans

● Groundwater- water held underground in the soil or in porces and crevices in rocks ● Transpiration- evaporation of water from plant leaves ● ● ● ● ●

Over oceans: more evaporation than precipitation so… oceans should be drying up Overland: more precipitation than evaporation so.. Land should be flooded by water But equilibrium exists between these 2 excesse Surface runoff of excess precipitation over land is equivalent to excess amount of evaporation over oceans---keeps oceans at generally same level Except for effects of changing global climate*

What is a drainage basin? a drainage divide? Know the four patterns of river drainage and the geologic setting in which they occur ● ●

Watershed (drainage basin): area over which if precipitation falls it would be drained by rivers in that basin → drainage divide separates watersheds Drainage patterns ○ Within watersheds--rivers and streams can flow in different patterns ■ Dendritic ● Like branches of tree, tributaries flowing into main channel, created when rivers/streams flow through common rock type ■ Rectangular ● bend/curve at nearly right angles, created when rivers/streams flow along fractures or joints in rocks ■ Trellis ● Rivers and tributaries flow parallel to each other for long distances, occur when rivers flow in valleys of folded rocks ■ Radial ● Flow away from a central uplift (e.g volcano)

What is a longituidinal profile? How does the longituidinal profile of a river or stream change from its headwaters to its mouth?What is stream gradient? How does the gradient of a stream change downstream?Longitudinal Profile & Gradient ● ●

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Longitudinal profile: plot of elevation of river from head (source) to mouth (end) Gradient: change in elevation as function of distance from head (source) to mouth (end of a river) ○ Gradient decreases from head to mouth gradient=(elev.1-elev.2) divided by horizontal distance between 1 & 2

What is discharge? How does the discharge of a stream change downstream? Know that the velocity of a stream is dependent upon both discharge and the stream gradient What are the typical downstream changes in velocity – what causes these changes? Discharge ● Amount of water flowing past given point in given amount of time ● Discharge increases from head to mouth Gradient & Discharge ● Higher (steeper the gradient): faster river/stream velocity→ since gradient decreases downstream impact on velocity is to decrease ● Higher the discharge: faster river/stream velocity: since discharge increases from head to mouth impact on velocity is to increase ● Factors (gradient decreasing, discharge increasing) compete in terms of impact on velocity from head to mouth ● Near head- high steep gradient is more important factor: velocity of stream relatively

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high Near mouth- high discharge is more important factor-velocity of stream relatively high Why care about discharge of river/stream? ○ Impacts capacity of river/stream -capacity is maximum amount of material that transport agent (Water) can carry (as suspended load)-higher the discharger -higher the capacity

Know the ways that a river or stream carries the debris of erosion What is competence? What is capacity? Competence & Capacity ● Impacts competence of river/stream-competence is maximum grain size that transport agent (water) can carry (as suspended load) -higher the velocity -higher the competence ● rivers/streams carry weathered rock material in 3 ways ○ 1. Bed and saltation load (along bottom or bouncing along bottom) ○ 2. Suspended load (flowing along with water) ○ 3. Dissolved load (dissolved in water)

What is a floodplain? ●

Floodplains-area over which river/stream meanders, can be covered during a flood

What is a meander? Point bars? Oxbow lakes? ●

Meanders-bends or curves in river/stream, water velocities are lower on inside of meander and higher on outside of meander ○ Inside: lower velocity, lower competence, deposition occurs -deposits called point bars ○ Outside: higher velocity, higher competence, erosion occurs, can form ox-bow lakes (abandoned meanders in river/stream)

What is a natural levee? ●

Natural levees: deposits that occur along banks of river/stream created during floods when river/stream overflows its banks (velocity decreases outside of channel, lower competence)

How do you determine the recurrence interval for floods?What does it mean to have a 10-year flood?During what flood cycle does the river do most of its work of erosion and transport? ●

Floods ○ Flooding is common event for river/stream on average will reach channel-full at least once a year --floods every 2 to 3 years --during 2 to 3 year flood cycles river does most work of erosion and transport ○ X year floods--e.g., 10-year, 50-year, 100-year floods refers to probability that

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only once in the next X-years will flood with discharge equal to or greater than flood occur again (probable, not certain) X-year floods are called recurrence interval-determined by measuring maximum discharge from river’s floods over long period of time

What is a delta? ●

Deltas: deposits that occur when river/stream flows into standing body of water (lakes or ocean) --Velocity of river/stream is decreased to zero

What is an alluvial fan? ●

Alluvial Fans: deposits that occur when sudden decrease in gradient of river/stream occurs, for example when river flows from mountain into valley

Know that, in terms of the features formed at the surface of the Earth, water is the most important agent of transportation, erosion, and deposition for weathered material Groundwater - Chapter 11 in Physical Geology What are permeability and porosity? Used to describe how water flows through surface... ● ●

Porosity=measures of amount of void spaces in material (percentage) Permeability=measures of “interconnectedness” of void spaces in material (ratio)

What is an aquifer? an aquiclude?What is the water table?What are the zone of aeration (unsaturated or vadose zone) and the zone of saturation (saturated zone)? What is a confined aquifer? an unconfined aquifer? ● ●

Materials groundwater can easily/not easily flow through… Aquifers=material through which water can easily flow (e.g, sandstone-high porosity and permeability) Aquicludes=material through which water cannot easily flow (e.g, shale-low permeability)

Aquifers ● Unconfined aquifers-aquifer receives water from earth’s surface ● Characterized by zone of aeration (pores filled with air or partially filled with water/air) and zone of saturation (pores filled with water) ● Water table-boundary between zone of aeration and zone of saturation -don’t always stay at same depth--move up and down depending on amount of water in system

What is a perched water table (aquifer)? ●

Occurs

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where, due to lens of sediments acting as aquiclude, secondary water table is located above main water table Ground water collects on top of that layer and can’t flow through zone of aeration =forms perched water table, sitting above the main water table Controlled and positioned by presence of an aquiclude When the water in perched table intersects the ground surface, water will flow out ○ Can generate a spring =natural source of water, flowing from a water table into the stream system flowing downhill into stream

What is hydraulic head?How fast does groundwater move? Groundwater =water flowing beneath land surface ● Incredibly important & most abundant freshwater resource to earth’s 7 billion humans ● Flows slowly-typically centimeters (inches) per day -flows in direction determined by changes in hydraulic head (water pressure relative to elevation datum)-flows from high to low head ○ Groundwater will flow from above river/stream, follow pressure of water and then sometimes flow upward when it comes in contact with river and stream because follows pressure difference--area of high or low pressure

What is a cone of depression? Well ● ●

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Where groundwater is brought to surface Cone of depression ○ Local lowering of water table around well due to removal (pumping) of groundwater to surface Well require naturally, have to drill down, water will not naturally rise up, have to pump it up

What conditions lead to an artesian well? Artesian Wells ● Groundwater comes to surface without having to pump ● Upper layer preventing water from entering above and below ● Recharge area is where water comes in from rain water ● Drill well into confined aquifer, water naturally flows up to surface --don’t have to pump ● Conditions ○ Confined aquifer (aquifer between 2

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aquicludes) Confined aquifer is inclined Recharge area above height of well

How are caves formed? What are stalactites? Stalagmites? What are sink holes Groundwater & Limestone ● Groundwater flowing through subsurface if encounters limestone (calcite) will leach (dissolve away) rock (think dissolution) → forming caves Stalactites, Stalagmites & Sinkholes ● Features associated with caves include … ○ Stalactites (deposits formed on top of caves) ○ Stalagmites (deposits formed on floor of caves) ○ Sinkholes (collapse above where limestone has dissolved away) ● ^Result of groundwater flowing thru cave and reacting with material/dissolving some limestone and precipitating out, build up over time

What is karst topography? What is leaching? ●

Formed in areas dominated by limestones where large amounts of leaching/dissolution occur ● Only little blips of rock left Characterized by irregular shaped mountained with intervening valleys

What is salt-water encroachment? How does it occur? ● ● ● ● ● ●

Along coastlines where groundwater is withdraw from wells There is fresh water below oceans salt water encroachment can occur salt water replaces fresh water -contaminated wells Instead of salt water → confining unit → fresh water Encroachment causes… ○ Salty water → confining unit → salt water

What are typical amounts of dissolved material in potable groundwater? What are the effects of these dissolved materials on the quality of the water?What are the sources of groundwater contamination? Types/sources of groundwater contamination ● Old landfills ● Septic tanks ● Mine waste ● Waste lagoons ● Chemical (gas) storage tanks ● Fertilizers

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Pesticides Salts on roads

Groundwater contamination ● Potable water --water that is drinkable with low risk or harm ● Dissolved water (including contaminants) are typically measured in water in concentrations of parts per million (ppm) or parts per billion (ppb) ○ ppm=1 part dissolved, 999,999 parts water ○ ppb=1 part dissolved, 999,999 parts water

Types of groundwater contaminants ● Defined by environmental protection agency (EPA) ● 6 major categories ○ Microorganisms, Disinfectants, Disinfection byproducts, Inorganic chemicals, Organic chemicals, Radionuclides

Glacial Systems – Chapters 12 and 21 in Physical Geology What is a glacier?What percentage of the Earth's surface is presently covered by glaciers? What are two general types of glaciers Large masses of ice moving downhill under influence of gravity-move at average rates of 1 meter/day ● Can surge and move much faster (several meters/day) ● Glacial ice covers 10% of earth’s surface 2 major types of glaciers ● Continental glaciers ○ Cover large continental areas --Antarctica, Greenland ● Valley Glaciers Cover mountainous areas (flow within valleys)

Understand the processes that lead to the formation of a glacier 1) high latitudes and high altitudes 2) snow accumulation 3) granular snow 4) firn 5) glacial ice Know how a glacier moves 1) downhill 2) internal flow 3) basal slip 4) crevasses How fast does a glacier flow? What are surges?

What is the competence of ice when compared to water? What is the capacity of ice when compared to water? Know the erosional features of valley glaciers ● ●

Glacial ice moving downhill erodes large amounts of rock Glacial erosional features include ○ U shaped Valleys ○ Cirques: bowl-shaped depression, located at source area of glacier ○ Horns: triangular to pyramidal shaped mountain peaks caused by glacial erosion on all sides ○ Aretes: sharp, razor-edge (steep slope-very rapid change in elevation), ridges of rock caused by glacial erosion ○ Hanging valleys: elevated glacial valleys where former glacier tributaries entered main glacial valley ○ Fjords: glacial valleys flooded by seawater ○ Glacial striations: scratches and grooves gouged in rocks as ice passes

Know the depositional features of valley glaciers Glacial Depositional Features ● When glacial ice stops advancing, deposits rock material that was transported ● Drift: all sediment of glacial origin found anywhere on land or sea floor ● Till: drift deposit from ice melting, heterogenous mixture of particle sizes, not layered by grain size ● Outwash: drift deposits from meltwater flowing away from glaciers, layered by grain size (big on bottom, small on top) ● Moraines: ridges of till ● Lateral moraine: till along side of glacial valley ● Medial moraine: formed where two glacial valleys are joined, occur within ice of glacier ● End moraine: till deposit where glacier stopped and began to melt ● Terminal moraine: end moraine that marks furthest position of glacial advance ● Ground Moraine: random till ● Features near terminal and end moraines ○ Drumlins: smooth, elongated ridges of till, orientation tells direction of ice movement ○ Eskers: sinuous ridges of sand and gravel-deposited by glacial meltwater flowing beneath ice ○ Kettles(kettle lakes): depressions, created by isolated block of ice that melts after main glacier has retreated ○ Varves: cyclical layers of sediment deposited on seasonal basis (2 per year) in glacial lakes ■ Slit and fine sand deposited later spring and summer from sediment load from meltwater ■ Clay deposited from suspended load during winter months when meltwater is reduced and lake surface freezes

What happens to sea level during glacial and interglacial times? Know that we are currently within an interglacial time period during the Pleistocene Ice Age. How much lower was global sea level at the peak of the most recent glacial period in the Pleistocene Ice Age? ● ●

Pleistocene Ice Age During last 2 million years, earth’s climate has been relatively cold Globally cold enough that glacial ice could grow called Pleistocene Ice Age

Glacial Time Periods ● Within ice ages, periods of time when significantly colder (glacial ice grows)-these time periods called glacial time periods (10’s to 100’s of thousands of years) ● During glacial time periods, surface runoff decreases ○ Water tied up in ice ○ Global sea level decreases up to 40 m/120ft lower 10,000 years ago Interglacial Time periods ● Within ice ages, periods of time when significantly warmer (glacial ice melts) these time periods called interglaical time periods (10’s to 100’s of thousands of years) ● During interglacial time periods, surface runoff increases ○ Water tied up in ice melts and returns to oceans-also warmer ocean expands, greater ocean volume ○ Global sea level increases (up to 8m/24ft higher 120,000 years ago) Ice Ages ● Climate variations resulting in global warmer and colder temperatures have occurred throughout earth’s history-ice ages prior to pleistocene occured 2.4-2.1 billion, 850-30 million, 460-430 million, 350-260 million years ago ● Time periods between ice ages are on order of several hundreds to hundreds of million of years (longer term fluctuations in climate) Glacial and Interglacial Time Periods ● Time periods between glacial and interglacial time periods within ice ages are on order of tens to hundreds of thousands of years (shorter term fluctuations in climate) Causes of ice ages and glacial/interglacial time periods ● Climatic variations are due to 2 major processes ○ Longer term fluctuations due to plate tectonics ○ Shorter term fluctuations due to variations in earth’s orbit and rotational axis with respect to sun (Milankovitch cycles)

What is the cause for long-term fluctuations in climate? Plate Tectonics -Long Term Changes in Climate ● Working model based on 2 fundamental principles ○ 1. Outer shell of earth divided into series of 12 or so individual lithospheric plates ○ 2. Plates are in motion with respect to one another (relative motion) and with respect to underlying lower mantle (absolute motion) ■ Plates move at velocities of 2-16 cm/yr as fast as your fingernails grow ● Movements of plates and their interactions can dramatically influence climatesmovements occur slowly but over long periods of time (hundreds of millions of years) can have major impacts -bring about changes into/out of ice ages ○ Ex: plate tectonics leading to onset of Pleistocene Ice age

What are the causes for short-term fluctuations in climate? What are Milankovitch cycles? Milankovitch Cycles-Short term Changes in Climate ● Changes in earth’s revolution about sun and changes in earth’s rotational axis ● 3 major milankovitch cycles ○ 1. Changes in eccentricity-Earth’s revolution about sun ○ 2. Changes in obliquity-earth’s rotational axis ○ 3. Precession-earth’s rotational axis ● Together these cycle acting over tens to hundreds of thousands of years can produce changes in earth’s climate (think glacial/interglacial time periods) Milankovitch Cycles-Short-term Changes in Climate 1. Changes in eccentricity of earth’s revolution about sun over time period of 100,000 years, earth’s revolution about sun becomes more/less elliptical ● Changes in eccentricity change amount of solar radiation reaching earth from sun 2. Changes in obliquity of earth’s rotation axis with respect to sun -over time periods on order of 40,000 years-earth’s angle of obliquity varies between 22.5 and 24.5

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degrees Changes in obliquity change intensity of solar radiation reaching earth from sun 3. Precession of earth’s rotational axis-over time periods on order of 20,000 years -earth’s rotational axis precesses ● Changes in precession change intensity of solar radiation reaching earth from sun ● Changes in eccentricity, obliquity, and precession occur at same time, but over different lengths of time ● Sum together to change climate over time periods an order of tens to hundreds of thousands of years

What is the greenhouse effect?What are the major greenhouse gases? ●

greenhouse gases in earth’s atmosphere absorb heat from solar radiation that has reflected off earth’s surface -keeps “heat” in atmosphere

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