GEOG 141 study guide 2015
GEOG 141 study guide 2015 GEOG 141
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Popular in Geography
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Climate systems chapter 10 Climate oscillations El Nino NAO PDO Multiyear oscillations in global circulation system uctuations or deviations from the norm causing interannual or decadal variability El NinoLa Nina southern oscillation ENSO Deviation from normal conditions in south paci c ocean Normal year Strong equatorial currents westward Low pressure in western paci c MalaysiaN Australia Upwelling of cold water along S American coast Peru replacing westwardmoving surface water El Nino year Equatorial current toward west weakens Low pressure moves to central paci c Upwelling of cold water stops along S America coast sea surface temps warm El Nino effects Global effects Occurrence every 35 years avg every 212 possible South America no upwelling shseabird die off Paci c Northwest warmer Californiasouthwest wetter La Nina cooler than normal conditions with stronger upwelling Paci c Northwest is wetter Californiasouthwest is drier 3E 15quot 15quot 3D 45 15W m9 an I II 1I IIII39TII39 3UP II 5 up 1i 5 3m illustra39lia high 45quot IEIZIE Ii E North Atlantic Oscillation NAO driven by pressure gradient between Icelandic subpolar low and Azores subtropical high Positive NAO strong gradient very low Icelandic low Very high Azores High Azores high centered in middle of N Atlantic Strong northtracking jet stream strong westerlies N Europe warm wet storms Eastern US winters less severe Negative NAO weak gradient Weaker Icelandic low Weaker Azores high Azores high closer to Europe Weaker more southern jet stream weak westerlies Arctic air moves south in N America N Europe cold dry winters Easter US cold snowy 200910 snowmegeddon Paci c Decadal Oscillation PDO driven by differences in sea surface temperature between the northern North Paci c gulf of alaska and the eastern north paci c west coast US North Paci c Ocean conditions rst described in 1996 On average there is a 2030 year time periods but shifts may be smaller Positive warm phase 19771999 20042007 Eastern North Paci c US west coast warmer Northern North Paci c Gulf of Alaska cooler Negative cool phase 19471977 19992003 2008 Eastern North Paci c cooler Northern North Paci c warmer PDO and salmon PDO negative phase correspond to higher salmon returns Weather vs climate Weather quotthe state of the atmosphere at a place and time in terms of temperature precipitation humidity Wind cloudsquot Our day to day experience of these elements Highly variable local Climate the average yearly pattern of weather across a region Drives vegetation patterns Drive hydrological patterns of rivers Shapes socialcultural patterns What variables and patterns in variables do we use to describe climate Key climate descriptors Temperature Average annual Min and maX range of variation Precipitation Total annual how much When does it fall uniform all year primarily Winter or summer range of variation Climograph demonstrates the relationship between temperature and precipitation Supply vs demand Surplus vs de cit Implications for vegetation and hydrology water supply and river ow Key factors driving climate regime of a region Latitude insolation amount seasonality Continental vs maritime Shape of continents and adjoining ocean basins Position relative to key high and low pressure cells ITCZ subtropical highs subpolar lows Position relative to global Winds and ocean currents Mountains Koppen vs Thornwaite classi cation system Koppen classi cation system Most Widely used Based on regional temp and precipitation Used vegetation boundaries to create different categories Advantages Straightforward to measure and classify Variables measured most often Divided into six major climate zones A humid tropical B arid and semiarid C humid mesothermal or temperate mild winter D humid microthermal or cold E polar H highland Hierarchical six major climate zones subdivided by factors such as Seasonal precipitation distribution yearround vs monsoonal vs summer dry vs winter dry Temperature of a given season eg hot vs warm vs cool summer Yearround moisture availabilityde cit for aridsemiarid zone B Thornwaite classi cation system Based on water availability demand and use by plants and natural systems Potential evapotranspiration demand Actual evapotranspiration actual use Water de cits Often used by plant ecologists soil and water resource scientists Know the six major climate zones and understand the key causal factors for each Six major climate zones A humid tropical B arid and semiarid C humid mesothermal or temperate mild winter D humid microthermal or cold E polar H highland Key causal factors of each A Consistent day length and insolation year round Warm ocean unstable rising air masses ITCZ and its migration in uence rainfall pattern B Dominant presence of dry subsiding air Subtropical high pressure cells arid deserts Shifting subtropical high pressure cells semiarid steppes Continental interiors far from moisturebearing air masses Rain shadows of mountain ranges C Latitudinal effect on insolation and temp Continental vs maritime effects Shifting of maritime and continental air masses Migration of low and high pressure systems migrating high pressure can result in dry summers Effects of sea surface temp on air mass strength Cooler temp on west coasts weaken air masses D High seasonal variation in insolation with increasing latitude sun angle day length Continental interiors cP air mass source dominate winter Westerly winds bring warm air north cold air south Cyclonic activity Convectional thunderstorms from mT air masses Asian winterdry associated with continental high pressure E Energy de cits due to Low sun angle even during continuous summer daylight Dark winters High surface albedo re ects SW radiation H Elevation Know the general characteristics of the climate types within the major climate zones and be able to distinguish climographs between them Tropical rain forest tropical monsoon tropical savanna humid subtropical hot summer humid subtropical dry winter marine west coast Mediterranean humid continental hot summer humid continental mildsummer subarctic tundra ice sheet desert hot desert cold steppe hot steppe cold highland A Tropical climate zone gtCharacteristics Abundant yearround or seasonally intense rainfall Impacted by tropical cyclones Tropical rainforest climate g eg Brazil steady temp and rainfall year round Less rain in fall The climograph for tropical rainforest steady temp all year round with constant precipitation Tropical monsoon climate eg India less steady temps A lot more precipitation in summer The climograph for tropical monsoon climate steady temperature year round although less steady than tropical rainforest Lots of rain during the summer months while in the winter it barely receives any Tropical savanna climate eg kenya pretty stable temp most rain in winter and spring The climograph for tropical savanna Steady temp all year round but a little less steady than tropical rainforest Not a lot of rain in the summer Most rain in the spring B Dry arid climates gt Characteristics Water demand is a lot greater than water supply from precipitation Key point both hot and cold desertssteppes Arid deserts hot 8 subtropical eg Saudi Arabia high temps especially in the summer months Barely any precipitation most of it during winter months Climograph for hotampsubtropical arid desert very little precipitation None in summer months Temperatures go from 16 C in winter to 40 C in summer Arid deserts cold 8 midlatitudel eg New Mexico temp raises in summer Most precipitation in summer More precipitation than hot and subtropical arid deserts Climograph for coldampmidlatitude arid desert More precipitation year round than hot arid desert but is still very dry There is precipitation in every month most of it in the summer Temps go from 4 C in the winter to 26 C in the summer Semiarid steppes hot 8 subtropical eg Australia about the same amount of rainfall each month Temperatures are high but drop during the NH summer months Climograph for hotampsubtropical semiarid steppe In the southern hemisphere s winter temp drops to 10 C from 27 C in the summer Precipitation is about equal in every month but there is not a lot Semiarid steppes cold 8 midlatitudel eg western Canada Temp is low but peaks in the summer months No rainfall in the winter All rainfall in spring and summer and fall Climograph for coldampmidlatitude semiarid steppe Temp goes from 7 C in the winter to 16 C in the summer There is no precipitation in the winter There is precipitation in the spring summer and fall but not much C Humid mesothermal climates gt Characteristics Temperatewarm cool to hot summers cool to warm winters Variable precipitation moist all year vs dry summer vs dry winter Greatest weather variability because greatest air mass interaction tropical cyclones and midlatitude cyclone systems Warmer temp on east coasts strengthen air masses Humid subtropical hot summer moist all year eg Georigia USA constant precipitation year round Temp raises in the summer months Climograph for humid subtropical hot summer temperatures rise from 4 C in winter to 27 C in the summer Most precipitation in summer but it is moist all year Humid subtropical winterdry hot to warm summers eg China wet summer dry winter due to monsoon effects Temperature raises during summer months Climograph for humid subtropical dry winter Temperatures from 5 C in winter to 26 C in summer Winter less wet Summer months very wet Mediterranean dry summer eg San Francisco USA dry summer due to migrating subtropical high pressure cells Wet winter Temp raises in summer Climograph for mediterranean dry summer Temps go from 10 C in winter to 27 C in summer Precipitation in winter spring and fall but not in the summer Marine west coast eg Ireland mild winters cool summers Maritime polar air masses Coastal fog Less precipitation in the summer more in the winter Climograph of marine west coast similar to mediterranean dry summer except there is more precipitation year round including summer D Humid microthermal climates gt Characteristics Cold winter season Cool to hot summers Moist all year or dry winter Increasing seasonality and great temperature ranges Humid continental hot summer eg china or New York in NY moist all year In china dry winters moist summers Both places increase in temp during summer months Climograph for humid continental hot summer Temps go from 1 C in winter to 24 C in the summer Precipitation is moist all year except in China the winters are more dry to to monsoon effect Humid continental mind summer eg Moscow Russia constant precipitation but a little more in the summer Temp raises in the summer Climograph for humid continental mild summer temps go from 8 C in winter to 18 C in summer Some precipitation all year round most in the summer months Subarctic cool summer eg Churchill Canada precipitation all year Temp raises in summer Climograph for subarctic cool summer temps go from 25 C in winter to 13 C in the summer Little precipitation year round but more in the summer and fall E Polar gt Characteristics No true summer sun angle always low Temp is never greater than 10 degrees C Temps too low for tree growth Extremely low humidity and precipitation Tundra Extremely short 23 mo summer with temps greater than freezing Permafrost soil Only in NH More precipitation than ice sheets Consistent year round Warmer than ice sheets Ice sheets Never above freezing Permanent ice cap Primarily Greenland and Antarctica Precipitation consistent year round H Highland gt Characteristics Even at low latitudes effects of elevation can produce tundra or polar conditions Distinct from polar climates signi cant precipitation Orographic uplifting Interception of humid air masses What is distinct about the climate in the Willamette Valley We are in between a marine west coast and mediterranean climate Climate change Chapter 10 amp 17 Methods used to construct past climates and what time scales each method can tell us about overall trends in past climates Tools for reconstructing past climate Dendrochronology tree ring analysis 100 s to 1000 s of years Oldest tree 5000 years Longest chronology 8000 years Bigger rings indicate rainy season narrower rings indicate drier seasons Coral reefs 100 s of years Pollen analysis lake sediments 1000 s of years Ice cores 800000 year record Ocean sediments 200 million year record Overall trends in past climates greenhouse effect vs icehouse earth glacial vs interglacial periods the medieval warm period and little ice age and how the present climate and trends compare with the past Past climate very long time scale gt 500 million years to present Past climate 100000 years to present Mostly glacial periods with brief interglacial periods Currently in interglacial Medieval warm period 1000 years ago 1300 AD Little ice age came right after medieval warm period 1350 to 1850 Greenhouse effect and icehouse earth are the two climate states states that the earth uctuates between During greenhouse earth there are no continental glaciers on the planet mainly caused by volcanic activity releasing C02 due to tectonic plate movement Icehouse earth is the earth in an ice age Ice sheets are present and greenhouse gases are less abundant Cause most likely due to less C02 in atmosphere Currently carbon dioxide and other greenhouse gases are increasing and the climate is warming faster than ever in recorded history C02 rising at 4 a year Agreement between measured C02 and ice core C02 Increases in carbon dioxide follow recorded carbon emissions There has been a long term correlation between rising C02 and rising temps Current effects of climate change eg sea level glaciers ice sheets species distribution Shrunken glaciers Ice is breaking up Plant and animal ranges have shifted Sea level rising more intense storms Droughts Floods Decreased airwater quality Greenhouse gases C02 and links to climate change why do we think greenhouse gas emissions are a primary cause of climate change C02 has always correlated with rising temperatures Over the last 10000 years when the holocene began changes in nitrous oxide methane and carbon dioxide were recorded all were relatively steady until about 130 years ago when the industrial revolution began when they began to sky rocket and since then the temperatures have begun to climb Future predictions what are some possible impacts of weather and society Sea level rise will directly impact coastal cities islands More frequent and intense weather events Shifts in species distributions extinctions Droughts Shifts in agricultural zones Likely to impact venerable peoples and nations the most Dry places may get drier Wet places may get wetter Changes in hydrological cycle Adaptation vs preventionmitigation what39s the difference Ecosystem essentials Ch 9 18 19 Hydrological cycle This cycle involves the circulation and transformation of water throughout earth s atmosphere hydrosphere lithosphere and biosphere Hydrological cycle and water budgets Inputs precipitation water and snow Where does it go Evaporation landwater Transpiration Storage soil What happens when the soil lls up or can t store things fast enough Groundwater subsurface ow Surface runoff Evaporation or evapotransipiration gt cloud formation gt precipitation gt runoffgroundwater ow gt back to ocean or lake etc gt evaporation Most evaporation occurs in the ocean 86 while 14 comes from the land which includes transpiration Photosynthesis respiration net primary productivity transpiration and evapotranspiration Plant photosynthesis takes in C02 light and water and releases 02 that goes into the atmosphere and sugar which goes into plant growth g mu Milt solar enlemw timidFa Plant respiration takes in 02 from the atmosphere and releases H20 and C02 into the atmosphere and energy into plant growth LLquotEn1 UE T U1 LUquot T H T HIIHIEV Net primary production NPP net photosynthesis for an entire plant community It is highest in tropical forest areas along the equator l l Energy remained I Hesp iraiinn If HETDiiM FE hut uni used nansumptinn Plant hiumaas remaining Utilization by plants i spnsiiinn all net primary gpr ll li r l Transpiration happens when water is taken up from the roots of a plant and the water moves up through the xylem vessels in the stem which conducts water and minerals to the leaves Then the water escapes through open stomata mainly on the underside of leaves This is to cool the plant and perform gas exchange Evaporation the net movement of free water molecules away from a wet surface into the air that is less than saturated Evapotranspiration evaporation and transpiration combined It is the sum of eval and transpiration from the earth s land and ocean surface 14 occurs on land Soil water balance equation know this precipitation supply soil water storage surplus goes to surface runoff and groundwater Soil Water Balance Equation P precipitation AET actual evapotranspiration ASTOR storage SURPLUS HRHQEP U m 1 WITIEFEEIEE TESL V im rt 14m 1130 1 ED milizafti n 1i 1 El i l iii EU EU SIDill miniature in E39U gain immigrating liming ED 5D E iImi iur FEEi IEIJirQE39 L a 55 4321 EU 11 2D i JAN FEB MAR APP M i f JUN JLIEL UE EEF NEE139 2541 r39n39im 2 1 iii quotPI 1 Eu mJl uE PHEEP Fl Enilgmaistwe Ulz li l DEW FEDTET r E illm iisiur e wrenhaargie v FEETET quotA Relationship between Potential evapotranspiration demand Actual evapotranspiration and water de cit AET actual evapotranspiration PET potential evapotranspiration DEE water de cit or PET AET DEE PET Demand Precipitation Supply What factors drive potential evapotranspiration temperature humidity wind how Evapotranspiration increases with Wind and temperature Decreases with increasing humidity Know general patterns of precipitation and potential evapotranspiration across US Generally when there is more precipitation in one place there is less potential evapotranspiration PET in that place So in the paci c northwest USA where this is a lot of precipitation gt80quot there is less PET 2430quot which indicates a BIG surplus is water In the southwest USA there is little precipitation lt10quot and a lot of PET gt60quot thus indicating a BIG de cit For example look at this annual water budget graph from Arizona TIEHISI HE D F TIEE39 ME TIES EIEEi 7 ME THEE Elli F ESI E1 5 till 33953 E 3911 2 S il mmmur e WWI Sign Immune my lJ39LEsl FEB MAR Jill JR quot191Mquot JJ39FE lLJL EEE EEC 1 Willi DEE E Ph ixm Ariz na E Surplus PREEIP Eihrnoistuwu utilization Dig FFJTET Emilmoisture rec hrge AELTET efivm 3954 mm T in Be able to interpret annual soil water balance graph and distinguish between water balance patterns for key climate types Soil Texture what are the different types of soils as de ned by texture and what are the components of soil silts clays sands Silt between sand and clay whose mineral origin is quartz and feldspar May occur as sediment or soil mixed in water Clay more ne grained rock or soil Has many small pores to tightly hold water against gravity Sand granular material composed of rock and mineral particles bigger particles than silt or clay Few small pores and little aggregation to hop water against gravity Soil is composed of minerals sandsiltclay organic matter water and air Relationship between soil texture and water availability for plants eld capacity vs wilting point why do loams have best eld capacity Soil texture is important for determining water retention and water transmission rates Plants operate most efficiently when the soil is at eld capacity which is the maximum water availability for plant use after large prose spaces have drained of gravitational water Soil type determines eld capacity the depth to which a plant can send its roots determines the amount of soil moisture to which the plant has access If soil moisture is removed below eld capacity plants must exert increased energy to obtain available water This moisture removal inefficiency worsens until the plant reaches its wilting point Beyond this point plants are unable to extract the water the need and they diequot Loam has the best eld capacity because it is a mix of sand clay and silt It is a medium textured soil and because it s a mix of the three main soils it has many pores that hold water against gravity Capillary water water that is available to plant roots held in soil by weak hydrogen bonds Maximum capillary water in soil eld capacity Gravitational water Drains out quickly to streams or groundwater Carbon Cycle and what is the largest carbon storage sink on Earth Carbon cycle oil gas and coal extracted from earth s surface l Burning of forests fuel wood and organic debris create C02 also respiration and decaying organic matter I C02 gas in atmosphere I taken in by trees via photosynthesis taken in by the ocean ocean also experiences in ux of Calcium carbonate from limestone and dolomite in earth s surface I trees and phytoplankton in ocean release CO2 by respiration and decomposition and CO2 also released by human activities The largest carbon sink is the ocean Nitrogen cycle nitrogen xing plants and bacteria why are they essential to life on Earth fertilizers and quotdead zonesquot Nitrogen cycle gaseous nitrogen N2 in the atmosphere I nitrogen xed by nitrogen xing bacteria living in legume rood nodules or in the soil I converted into ammonium NI14 l nitrifying bacteria do nitri cation to convert NH4 to nitrites NO2 I nitrifying bacteria turn NO2 into nitrates N03 I NOB undergo assimilation in plants which animals eat or denitrifying bacteria turn NOB back into gaseous N2 I when animalsplants die the nitrogen in their body is decomposed and the nitrogen is turned into NH4 again Nitrogen xing plants in the Paci c Northwest alfalfa lupine red alder ceanothus What are the reasons that plants are critical to life on Earth and Earth s cycles hydrological carbon nitrogen Plants They are the critical biotic link between solar energy and the biosphere Very important Convert carbon dioxide to oxygen atmospheric 02 source Create store release carbon compounds carbon cycle Fix nitrogen nitrogen cycle Base of vast majority of food webs energy nutrient supply Key role in hydrological cycle transpiration Transpiration elevates atmospheric humidity Terms and Concepts Ecosystems Communities Ecology Biogeography Limiting Factors Niche Succession Primary vs Secondary Succession Disturbance Know key disturbance types Ecosystem a system formed by the interaction of biological communities with the abiotic environment in a given place Community groups of organisms populations of a given type that occupy a place and interact with each other Biogeochemical cycles The cycling of chemical elements essential for life between the biological and abiotic parts of Earth s systems Earth is a closed system in terms of matter these elements are neither created nor destroyed but continually transformed stored released and cycled through different parts storespoolsreservoirs of earth s systems atmosphere hydrosphere lithosphere biosphere Ecology the study of interactions among organisms and of organisms with their environment Biogeography focuses on the patterns of species the processes the create species patterns how and why are species distributedwhere are they Distribution of species causes Underlying environmental factors and gradients Limiting factor the one physical or chemical component that most inhibits biotic operations through lack or excess not enough water too much water too cold too hot not enough nutrients Disturbance regimes Succession and disturbance the cycle of life in a given place Succession the changes in community structure and composition species that occur over time as one group of species replaces another It is initiated by a disturbance Primary succession occurs on newly eXposed surfaces eg volcanic lava or glacial deposits after glacial retreat Secondary succession there is some life left behind from a disturbance Disturbance anything that destroysclears a space eg re wind mass movements oods disease volcanoes Gives opportunity for new organisms to colonize Dispersal and historic factors Biomes Chapter g0 Plant forms trees shrubs herbs lianas epiphytes bryophytes also see Ecosystem lecture Structure and life forms of plants Life form of a plant refers to its physical structure size and shape Moss layer I Herb layer I shrub layer l tree layer going from shortest to tallest Leaf types broadleaf vs needleleaf evergreen vs deciduous advantages vs disadvantages Know the 11 biomes their general characteristics which climate types are linked to which biomes and especially what are the characteristic water budgets of each biome and how this drives what plants types are characteristic of the biome Biomes m Tropical rainforest Tropical seasonal forest Midlatitude broadleaf and mixed forest Needleleaf and montane forest Temperate rainforest Shrubland Mediterranean shrubland Savanna Tropical savanna Grassland Midlatitude grassland m Warm desert and semidesert Cold desert and semidesert Tundra Arctic and Alpine tundra Biomes are organized by actual evapotranspiration vs water de cits Tropical rainforests have high demand PET and high supply P thus a low de cit and high actual evapotranspiration AET Tundra has low demand and low supply thus a low AET and low de cit Desert has high demand and low supply thus low AET and high de cit Tropical rainforest Climate tropical rainforest Water budget surplus all year Small scale disturbance Broadleaf evergreen trees eg Lianas tree ferns epiphytes Thin bark Nutrient poor soils High diversity rarity Tropical seasonal forest and scrub Climate wetdry tropical types monsoon tropical savanna Water budget Seasonal surpluses summer ITCZ and de cits winter Consistent high water demand seasonal water availability Semideciduous broadleaf forests lose leaves in dry season Medium stature trees openings with shrubs and herbs Mediterranean shrubland Climate Mediterranean Water budget seasonal surpluses winter and de cits summer Shrubs and herbs dominate some trees Growth limited in growing season Evergreen leaves common Drought adaptations sclerophyllous leaves Low surface areavolume ratio Thickened waxy Hairs underneath Fire adaptations Resprouting with deep roots Protective bark Tropical savannas Climate tropical savanna Transitional between seasonal tropical forestscrubland and semiarid hot steppesarid deserts climates Water budget tends towards de cits seasonal water availability Grasses with sparse trees Trees deciduous Small leaves often with thorns Midlatitude grasslands Climate semiarid steppes hotcold Humid subtropical hot summer humid continental hot summer Water budget tends toward de cits but rain occurs during growing season Draws heavily on soil storage Deserts cold and hot Climate arid desert cold and hot Semiarid steppe cold and hot Water budget chronic de cits irregular precipitation Sparse vegetation with adaptations for extreme drought Ephemerals with dormant seeds Succulence to store water Long deep taproots or spreading roots Waxy coatinghairs Re ective surfaces Defense thornsbad taste Soil toxins Tundra Climate tundra and highland high latselevation Water budget low supply but low demand Much of the water demand met by melting of frozen soils poor drainage Dwarf shrubs herbs mosses lichens Limiting factors on growth short growing season low insolation limited rooting space poor soils Midlatitude broadleafmixed forests Climate humid subtropical hot summer winter dry Humid continental hot summer Marine west coast in Europe Water budget maXimum demand PET and supply precip coincide seasonally in summer Surplus of water in the winter Sufficient soil water for plant use in summer Leaves bene ts vs costs and productivity vs conservation Deciduous broadleaves sometimes mixed with needleleaf trees maple oak ash walnut elm birch Spring ephemerals herbs Windstorms are a key disturbance Fire may play a role in proportion of pines vs deciduous Needleleaf and montane forest boreal Climate humid continental mild summer Subarctic Highland Water budget low demand PET moderate supply P No de cits Summer moist soils Winter waterlogged or frozen soils Limited species tall conical needleleaf usually evergreen Spruce fir pines douglasfir larch Low sun angles High snow loads Deep shade at ground level Temperate rainforest Climate marine west coast Water budget surpluses late fall through late spring Windward sides of mountains near coast Mild winters and summers Largest trees on earth Epiphytes Plant adaptations to arid Desert biome or dry summers Mediterranean biome climates Long deep tap roots Succulence Spreading root systems to maximize water availability waxy coatings and ne hair on leaves to retard water loss and lea ess conditions during dry periods Re ective surfaces to reduce leaf temps Tissue that tastes bad to discourage herbivores Tropical Savannas and Midlatitude Grasslands why grasslands in these climate types Grass life form as a strategy climate with water de cits and short wet growing season Feedback with large mammals Feedback with re Why do needleleaf evergreens dominate our region Weathering Karst Landscapes and Mass Movement portions of Chapter 13 Weathering concepts and terms regolith bedrock sediment denudation geomorphology mass wasting rock jointingfractures climate role of vegetation granular vs joint block separation differential weathering spheroidal weathering RegolithzThe upper surface of bedrock which undergoes continual weathering creating broken up rock called regolith Bedrock the parent rock from which weathered regolith and soils develop Sediment unconsolidated fragmented material ranging from ne clay silt sand to course gravel boulders size Geomorphology the science of landforms their orientation evolution form and spacial distribution Mass wasting sometimes used interchangeably with mass movement It is the general process involved in mass movements and erosion of landscape Mass movement refers to anat unit movement of a body of material propelled and controlled by gravity Cohesion gt material type Friction gt reduced with water Driving force gtweight size of material Rock jointingfractures jointing in a rock is important for weathering processes Joints are fractures or separations in rock that occur without displacement of the slides This increases the surface area of the rock for more exposed weathering Climate precipitation temp and freezethaw cycles are the most important factors affecting weathering Role of vegetation vegetation protects rocks from some raindrop impact and providing roots to stabilize soil but it also produces organic acids from the partial decay or organic matter these acids contribute to chemical weathering Granular vs joint block separation Denudation any process that wears away or rearranges landforms such as weathering mass movement erosion transportation and deposition Differential weathering the difference in degree of discoloration disintegration etc or rocks of different kinds exposed to the same environment Spheroidal weathering a type of chemical weathering chemical breakdown of the constituent minerals in rock always in the presence of water The sharp edges and corners of rocks are rounded as the alteration of minerals progresses through the rock Physical weathering frost action thermal stress salt crystal growth pressure release jointing sheeting exfoliation domes abrasion roots Frost action AKA freezethaw frost wedging Note rocks often have joints Most important weathering processes in cold climates Precipitation makes its way into crevices in rocks and it freezes at night Since frozen water expands this breaks rocks over time Thermal stress Expansioncontraction due to heatingcooling of rock material Different minerals within rock expandcontract at different rates Outer layers heat more expand more than inner layers Note granular disintegration vs joint block separation Granular disintegration gt spheroidal weathering Saltcrystal growth Slow evaporation of groundwater seepage leaves salt crystals Growing crystals break rock apart grain by grain Important in arid environments Granular disintegration Pressurerelease jointing AKA unloading First intrusive bodies eg granite formed by cooling magma within crust Under tremendous pressure from overlying material Pressure released as overlying material erodedremoved Outer parts of rock expanded Expansion creates stress Abrasion rocks moving water or ice hitting other rocks Potholes and bedrock smoothing Roots Note plant roots also pay role in chemical weathering exude organic acids Chemical weathering hydration hydrolysis oxidation dissolution of carbonates Hydration and hydrolysis amp oxidation both change minerals into new minerals gt softer and bulkier and more susceptible to erosion Hydration Little chemical change water combines with mineral but mineral can the dehydrate return to original form Hydration expansion dehydration gt granular disintegration Hydrolysis Chemical reaction with water sometimes with mild acids Causes decomposition of silicate minerals Granular disintegration gt as weaker minerals altered and crystal network breaks down Granular disintegration gt spheroidal weathering Oxidation Addition of extra oxygen molecule to a substance Iron Fe OZ Iron Oxide Fe203 gt rusthematite Oxidized substance eg iron removed from rock Crystal structure weakened Carbonation carbonic acid dissolves minerals washing them away in runoff Dissolution of carbonates AKA carbonation or carbonic acid acUon Water vapor C02 gt carbonic acid H2CO3 Rain with carbonic acid dissolves calcium carbonate CaCO3 Limestone marble vulnerable So when water vapor in the atmosphere mixes with C02 in the atmosphere it forms carbonic acid which harms calcium carbonate limestone Karst landscapes just know what it is general characteristics and causes Karst topography areas of limestone which are susceptible to chemical weathering which creates a speci c landscape of pitted bumpy surface topography poor surface drainage and well developed solution channels dissolved openings and conduits underground Weathering and erosion caused by groundwater may also result in remarkable mazes of underworld caverns Can create sinkholes caves and caverns Massmovement processes driving vs resisting forces angle of repose importance of water The driving force in mass movement is gravity and the resisting force is the shearing strength of the slope material AKA its cohesiveness and internal friction which work against gravity Mass wasting occurs when driving forces gt resisting forces Angle of repose steepness of resulting slope in which driving force and resisting force in balance 33 37 degrees The importance of water Types of mass movement and distinguishing characteristics speed of movement level of water saturation soil creep rock fall tallus slopes and cones debris avalanches ows debris ow earth ow mud ow landslides translational and rotational slumps Soil creep Slow and persistent Freezethawfrost heave gt surface expansion RockfaH Very high velocity not saturated with water During a rockfall individual pieces fall independently and characteristically form a coneshaped pile of irregular broken rocks in a talus slope at the base of a steep incline where several talus cones coalesce Debris avalanche Very high velocity not saturated with water Mass of rock debris soil May become uidized by icewater gt debris ow Distinguished from slides velocity Flows mud debris earth Flow saturated with water rapid typically move down valleys Mud ow mixture of soil ne sediment More uid than earth ow Debris ow a mixture of water rock and trees that amasses in a stream valley then ows downvalley with the consistency of wet concrete The speeds are usually much faster than earth ows and they carry large material Very saturated generally about 50 water Generally starts as a landslide or a debris avalanche but become saturated when it comes into the channel The ash ood quickly moves down a canyon picking up loose weathered matter eventually depositing the mud and rock at the mouth of the canyon in an alluvial fan Earth ow heavy rains saturate surface soil causing them to move downhill If the ground is not steep the ow can be fairly slow Like a slide it leaves a scar at its starting point but instead of sliding down a hillslope it ows as a thick mass with a steepsided bulging leading front Generally the soil surface looks irregular Landstes Rapid Not saturated but may be triggered by water Cohesive mass of regolithrock moves as a unit Large amount of material falls simultaneously Scar at starting point Irregular jumble of rock at end Translational slide moves along at surface parallel to slope angle No rotation Angularrectangular scar face Slumprotational slide moves along concave surface Leaves bowl shaped scar The Dynamic Planet Tectonics Earthquakes and Volcanism Chapter 11 and 12 supplemental Miller reading 1 General layers of the earth especially upper layers crust upper mantel asthenosphere composition and rigitidy uidness ocean vs continental crust isostasy and isostatic rebound Inner core gt outer core gt lower mantle gt upper mantle gt asthenosphere soft plastic rock Magma source gt lithosphere continental crust ridged Ocean crust density gt continental crust density Isostasy the equilibrium that exists between parts of the earth s crust which behaves as if it consists of blocks oating on the underlying mantle rising if material is removed and sinking if a material is deposited Isostatic rebound the rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period through the process of isostasy Exogenic vs endogenic processes Exogenic processes solar energy creates the activation of weathering due to water in the atmosphere Weathering slow breakdown of rock materials at and near earth s surface Erosion movement of weathered material and transport by Mass movement Water Wind Oceans Glaciers Endogenic processes tectonic plate movement caused by earth s internal heat and material Uplift Volcanism The Geologic Cycle hydrologic cycle rock cycle tectonic cycle Hydrologic cycle through erosion transportation and deposition the hydrological cycle processes Earth materials with the chemical and physical action of ice water and Wind The rock cycle produces three basic rock types found in crust igneous metamorphic and sedimentary Tectonic cycle brings heat energy and new material to the surface and recycles material creating movement and deformation of crust Minerals and rocks key elements silicates oxides carbonates Mineral inorganic nonliving natural compound having a speci c chemical formula and usually possessing a crystalline structure Rock assemblage of different minerals or assemblage of the same mineral Silicates one of the most widespread mineral families on earth because silicone and oxygen are so common and because they readily combine with each other and with other elements 95 earth s crust is made up of silicates eg quartz feldspar clay minerals gemstones Oxides oxygen combines with metallic elements such as iron for form hematite Fe203 Carbonates carbon in combination with oxygen and other elements such as calcium magnesium and potassium eg calcite CaCO3 a form of calcium carbonate Rock cycle amongst igneoussedimentarymetamorphic rocks Weathering erosion transportation and deposition of igneous rocks makes sediment gt sediment is compacted cemented and chemically altered to make sedimentary rock gt sedimentary rock is heated and intensely pressurized to make metamorphic rocks gt metamorphic rocks are melted to make magma gt magma is cooled and solidi ed for form igneous rocks Igneous rocks and processes magma lava intrusive vs extrusive felsic vs ma c what controls texturecrystal size plutons batholiths sills dikes basalt granite Igneous reformed rock a rock that solidi es and crystalizes from a molten state eg granite basalt Forms from magma molten rock beneath the surface Magma either intrudes into crustal rocks cools and hardens or it extrudes onto the surface as lava Intrusive igneous rocks that cools slowly in the crust forms plutons a general term for any intrusive igneous rock body that invades layers of crustal rocks The largest pluton form is a batholith an irregular shaped mass with a surface greater than 100 kmquot2 that form the mass of many large mountain ranges Smaller plutons that form parallel to layers of sedimentary rock are m and those that cross layers of the rock they invade are dikes cools slowly larger mineral crystals coarse grained texture eg granite Extrusive igneous rocks are on the surface cool rapidly smaller microscopic crystals ne grained texture Volcanoes surface ows eg basalt Felsic igneous rocks are derived both in composition and in name from feldspar and silica Felsic minerals generally are high in silica aluminum potassium and sodium and have low melting points Rocks formed from this are generally lighter in color and less dense than ma c mineral rocks Ma c igneous rocks derived both in composition and in name from magnesium and ferric Low in silica high in magnesium and iron and have high melting points Usually darker in color and of greater density than felsic rocks Sedimentary rocks and processes lithi cation process strata clastic vs chemical sandstone shale siltstone conglomerate limestone coal dolomite cements such as calcium carbonate Solar energy and gravity drive the process of sedimentation with water as the main transporting medium Smaller pieces of rock that eventually make up the bigger rocks are transported from high energy sites to low energy sites where they are dumped The formation of sedimentary rocks involves the lithification process of cementation compaction and a hardening of sediments Some examples shale compacted mud limestone lithified bones and shells or calcium carbonate that precipitated in ocean and lake waters sandstone cemented sand and m ancient plant remains that became compacted into rock Two primary sources of sedimentary rock are clastic and chemical sediments Clastic weathered and fragmented rocks that are further worn in transport There is a range of clast sizes from largest to smallest boulders rock form conglomerate gt pebblesgravel conglomerate gt course sand sandstone gt medium to ne sand sandstone gt silt siltstone gt clay shale Chemical are formed from dissolved minerals transported in solution and chemically precipitated from solution The most common chemical sediment is limestone lithified calcium carbonate derived from inorganic and organic sources A similar form is dolomite which is lithified calcium magnesium carbonate CaMgC032 Metamorphic processes heat and pressure but not remelting compressional stresses along faults examples such as shale to slate granite to gneiss basalt to schist limestone to marble sandstone to quartzite Any rock either igneous or sedimentary may be transformed into a metamorphic rock by going through profound physical or chemical changes under pressure and increased temperature Metamorphic rocks are generally more compact than original rock and therefore are harder and more resistant to weathering and erosion When subsurface rock is subjected to high temperatures and high compressional stresses over millions of years metamorphism can happen Igneous rocks become compressed due to slabs of earth s crust sandwiching them They may be sheared and stressed along earthquake fault zones causing metamorphism Metamorphic rocks may be changed both physically and chemically from the original rocks Shale turns to slate granite turns to gneiss basalt turns to schist limestone turns to marble Sandstone turns to quartzite Plate tectonics history of the idea and key evidence Pangaea sea oor spreading midocean ridges subduction zones divergentconvergenttransform boundaries hot spots History Alfred Wegener is known as the father of the concept of continental drift This came about in 1915 He believed that all landmasses formed one supercontinent about 225 million years ago He called it Pangaea which means all Earthquot Con rmation for this idea came about during the 1960s and the idea of plate tectonics became universally accepted as an accurate model for the way the earth s surface evolved Key evidence rocks of ancient mountain ranges past glaciations fossil record ocean mapping and dating Sea oor spreading the interconnected world wide mountain chain that drives continental movement It was said that these underwater mountain ranges were midocean ridges and the direct result of upwelling ows of magma Subduction zone convergent plate boundary occurs when continental crust and oceanic crust slowly collide and the denser oceanic crust will grind beneath the lighter continental crust Divergent boundary are characteristic of sea oor spreading centers and rift valleys on continents where upwelling material from the mantel forms new sea oor and lithosphere plates spread apart The spreading makes these zones of tension Example great rift valley in Africa and the Mid Atlantic Drift Convergent boundary are characteristic of collision zones where areas of continental and oceanic lithosphere collide continental plate and continental plate collide and oceanic plate vs oceanic plate collide Zones of compression and crustal loss a destructional process eg the Andes mountains the collision of India and Asia Transform boundary occur when plates slide laterally past one another at right angles to a sea oor spreading center neither diverging nor converging and usually with no volcanic eruptions Hot spot individual sites of upwelling material arriving at the surface in tall plumes from the mantle or rising from near the surface that produce thermal effects in groundwater and crust Know the relationship between the key plates on the West Coast Paci c North American Juan de Fuca Crustal formation cratons stable platforms continental shields terranes Cratons the nucleus or heartland region of the continental crust All continents have a nucleus on which the continent grows Generally have been eroded to a low elevation and relief stable Stable platform a covering of sedimentary rock on top of the craton Some tectonic activity Continental shield A region where a craton is eXposed at the surface No tectonic activity Terrane a fragment of crystal material formed on or broken off from on tectonic plate and accreted added to to crust lying on another plate Crustal deformation tension compression shearing reversethrust faults folding normal faults horst amp graben topography rift valleys strikeslip faultsd cause of Earthquakes Tension stretching normal fault rifts horstgraben Compression shortening folding reverse 8 thrust fault Shearing twisting or tearing Reverse fault or compression fault compressional forces associated with converging plates force rocks to move upward along fault plane Thrust fault If the fault plane forms a low angle relative to the horizontal Normal fault tension fault when forces pull rock apart Horst and Graben regions that lie between normal faults and are either higher or lower than the area beyond the faults Rift valley a liner shaped lowland between several highlands or mountain ranges created by the action of a geologic rift or fault formed on a divergent plate boundary Folding bending Convergent plate boundaries intensely compress rocks deforming them Strikeslip faults AKA transform fault vertical fractures where the blocks have have mostly moved horizontally eg San Andreas Fault Cause of earthquakes rock layers are stressed by tension along faults they will suddenly fracture and move to relive this stress The sudden motion along the fault produced an earthquake that shakes the ground surface Most sever earthquakes occur near plate collision boundaries Volcanic types processes and landforms explosive vs effusive lava vs pyroclastics surface lava ows shield volcanos composite volcanoes also called stratovolcanoes cinder cones caldera plug domes know key examples of different types molten rock Explosive high viscosity thick gt vent plugged Gases trapped gt boom 5075 siica Mt St Helens Melting of sub ducted ocean plate Effusive low viscosity magma uid Gases escape easily no eruption gentle Dark dense basalt lt 50 silica Hawaii sea oor Surface lava ows from ssures basalt most common Shield volcanoes gently sloping dome shaped cone eg hawaii islands Belknap Composite cones stratovolcanoes effusive explosive layers of lava pyroclastics ejected ash rocks Pyroclastics pulverized rock and elastic materials of various sizes ejected violently during an eruption Cider cone a small cone shaped hill usually less than 450 m high with a truncated top formed from cinders that accumulated during moderately eXplosive eruptions Caldera a large basin shaped depression Forms when summit material on a volcanic mountain collapses inwards after an eruption or other loss of magma Plug domes slow extrusion of viscous lava from volcano form within stratovolcano Mt Lassen CA 8 Mt St Helens Orogenesis mountain building i ocean plate continental plate collision orogenesis ii ocean plate ocean plate collision orogenesis iii continental plate continental plate collision orogenesis Orogenies literally means quotthe birth of mountains An orogeny is a mountain building episode occurring over millions of years Oceanic plate continental plate collision this is now happening along the paci c coast of the Americas and has formed the Andes the Sierra of Central America the Rockies At the heart of these mountains we see folded sedimentary formations with intrusions of magma forming granite plutons Their buildup has been augmented by capturing displaces terranes accreted during collision with the continental mass Ocean plate ocean plate collision This can be as simple as forming volcanic island arcs or more compleX arcs like Japan and Indonesia This includes deformation and metamorphism of rocks and granitic intrusions Continental plate continental plate collision large masses of continental crust are subjected to intense folding overthrusting faulting and uplifting The converging plates crush and deform both marine sediments and basaltic oceanic crusts Oldest to youngest orogenies appalachians 290 myagtrocky mtnsgthimalayasgtcascades 35 mya Key concepts uniformitarianism superposition catastrophism punctuated equilibrium Uniformitarianism this is the principle that assumes that the same physical processes active in the environment today have been operating throughout geological time Superposition rock and sediments always arranged with youngest layers superposed toward top and oldest at base if the have not been disturbed Catastrophism sudden short lived violent events that create some of earth s geological features In contrast with uniformitarianism Punctuated equilibrium we cannot see changes so there must be very long periods of no change River systems Chapter 14 last part of Chapter 9 and supplemental Strahler reading Groundwater aquifers aquicludes springs losing and gaining streams Groundwater an important part of the hydrologic cycle although it lies beneath the surface It is tied to surface supplies through pores in rock and soil It is the largest potential fresh water source in the hydrologic cycle It is not an independent source of water for it is tied to surface supplies for recharge Groundwter exists in zone of saturation and the water in the saturated zone can move Aquifer a rock layer that is permeable conducts water readily to groundwater to groundwater ow adequate for wells and springs Aquiclude a body of rock clay shale that does not conduct water in usable amounts impermeable Spring the result of an aquifer being lled to the point that the water over ows onto the land surface Losing stream a stream that loses water as it ows downstream The water in ltrates into the ground recharging the local groundwater the channel is above the groundwater Gaining streams a stream that gains water from groundwater The channel is lower than the level of the groundwater Terms drainage basin watershed drainage divide base level erosion transport deposition ephemeral vs intermittent streams Drainage basin every stream has one it is an area of land where surface water from precipitation runoff converges to a single point at a lower elevation Usually the eXit of the basin where the waters join another water body such as a river lake reservoir estuary wetland sea or ocean They are open systems Watershed drainage basin an area or ridge of land that separates waters owing to different rivers basins or seas The area of land where all of the water that is under it or drains off into it goes into the same place Drainage divide the line that separates neighboring drainage basins Base level a level below which a stream cannot erode its valley Erosion the process by which water dislodges dissolves or removes surface material The sediments eroded by the water are carried by mechanical transport and the sediments that are laid down are done by the process of deposition Ephemeral stream ow only after precipitation events and are not connected to groundwater systems Intermittent streams ow for several weeks or months each year and may have some groundwater inputs Stream discharge QAV or Qwdv how measured relationship between cross sectional area and velocity what factors effect discharge Width w Depth 1 Cross Section Area A Velocity v Discharge VolumeTime Q Slope or gradient 5 Sinuosity Index SI Discharge Q AKA ow the streams volume of ow per unit of time volume time in mA3s OR ftA3s Q wdv OR Q Av If you know discharge and area you can calculate velocity Since QAv v QA How do we measure discharge USGS gaging stations cross section area mapped velocities measured stage height measured in stilling well stage correlated to discharge Factors that affect discharge Area of drainage basin Precipitation amount and type snow vs rain Potential evapotranspiration Vegetation Rock type Landuse Velocity patterns within a stream cross section in general where fastest and relative to meandering bends in a river Why does velocity vary Fastest in a straight stream with steeper slope and smaller cross sectional area Slower in a meandering stream with less steep slope with larger cross sectional area Hydrographs pattern after rain event lag time peak ow urban vs natural storm hydrograph Hydrographs plots stream ow with time Peaks in hydrographstream recedes to base ow level after rain events Lag time between peak rain and peak ow Urban vs natural watersheds Urban 75 runoff 5 in ltration 20 evapotranspiration 70 100 impermeable Natural 10 runoff 50 in ltration 40 evapotranspiration 0 impermeable Bankfull ow and elevation ood stage vs bankfull base ow oodplains Bankfull high ows quotfillquot a stream to bank full every 12 years Floods are ows that exceed bank full height Floodplain the at low lying area anking many stream channels that is subjected to recurrent ooding Sediment sizes From smallest to largest clay silt sand gravel cobble boulders Sediment transport dissolved load suspended load bedload sliding rolling saltation dissolved load a solution of a stream especially the chemical solution derived from minerals such as limestone or dolomite or from soluble salts Suspended load consists of ne grained clastic particles bits and pieces of rock They are held aloft in the stream with the nest particles not deposited until the stream velocity slows nearly to zero Bed load refers to coarser materials that are dragged rolled or pushed along the streamed by traction or saltation Relationship between velocity and erosiondeposition and sediment size At high velocities rivers erode and transport sediment At low velocities sediment cops out and is deposited Larger particles require higher velocities to be moved Stream deposition types Bar accumulation of sediment Point bar midchannel Floodplain accretion vertical layering Alluvial fans Meandering rivers cutbanks point bars why do point bars and cutbanks develop meander movement with time meander cutoff oxbows meander scars natural levees Meandering stream stream with a snake like form and a gradual slope Cutbanks develop when the outer portion of each meandering curve that is subject to the fastest water velocity and therefore is eroded Point bars develop when the inner portion of each meandering curve lls up with sediment because the inner portion eXperiences the slowest velocity Meandering rivers move slower with time because the sinuosity goes up when a river is less straight it goes slower This is because meandering rivers become more exaggerated due to more deposition at point bars and more cut bank erosion Cutoff what is formed when the narrowing neck of land formed by the meandering river eventually erodes A cutoff marks an abrupt change in the stream s lateral movements the stream becomes straighter OXbows occurs when the former meander becomes isolated from the rest of the river It may gradually ll with organic debris and silt or may again become part of the river when it oods Meander scar formed by remnants of meandering stream Characterized by a crescent cut in a bluff or valley wall produced by a meandering stream They are often formed during the creation of oxbow lakes Natural levees low depositional ridges on either bank of some streams that develop as byproducts of ooding Braiding and braided rivers Braided rivers a river that is a maze of interconnected channels these occur due to excess sediment Braiding often occurs when reduced discharge lowers a stream s transporting ability such as after ooding or when a landslide occurs upstream Longitudinal pro le of streams steeper at headwaters and low gradient at mouth differences between upper middle lower reaches and delta Upper headwaters Steep gradient High velocity zone of erosion mass wasting sediment inputs high capacity for sediment transport Course sediments Middle reaches moderate gradient moderate velocity zone of transport moderately smooth channel alluvial deposits ood plains develop cut bank point bars Lower reaches minimal gradient low velocity deposition gt erosion ne sediments ood plains large m Flows into large body of water base level reached ow velocity greatly reduced zone of deposition Base level local vs sea base level what can change base level effects of base level change nickpoints see book for discussion of nickpoints Ultimate base level Sea base level is a level below which a stream cannot erode its valley sea level Because not all land has eroded to sea level there is something called local base level or temporary one that may be a lake river or reservoir Nickpoint the point of interruption on a waterfall or area of rapids that is an abrupt change in gradient Can create local base levels What can change base level tectonic activity and sea level change can change base level Effects of base level change alluvial terraces stream incision Stream gradation and evolution erosion and incision alluvial terrace development Stream erosion Hydraulic action turbulent ow captures sediments Abrasionattrition potholes Mass wasting largesmall events Stream incisionentrenchment alluvial terraces Old oodplain is too high connection lost left behind Incision caused by changes in base level and loss of sediment supply Stream gradation and evolution A graded stream has slope and size adjusted to have sufficient energy to transport its sediment supply Stream develops a graded pro le over time As river becomes graded valley walls become less steep Alluvial terraces are formed on both sides of the valley when an uplifting of the landscape or a lowering of base level rejuvenating stream energy so that a stream again scours downward with increased erosion Annual hydrographs seasonal timing of peak ows relative to different climate patterns seasonality of precipitation and de cits snow vs rain hydrograph a graph of stream discharge over time for a speci c location The graph shows the relationship between precipitation input and stream discharge Peak ow comes after precipitation event usually a storm with lots of precipitation In a desert the median daily statistic is zero but throughout the year unpredictably there will be peaks in ow Changes in hydrology with changes in temp Glacial landforms portions of Chapter 17 Glacial formation processes and terms Snow compression and recrystallization into glacier ice rn zone of accumulation zone of ablation equilibrium line sublimation calving Glacier mass of ing ice that has accumulated on land or oat as ice shelf in sea adjacent to land They are formed by accumulation of snow that recrystalizes under its own weight They are not stationary Formed when annual winter snow input gt summer loss ablation Key climate factors precipitation and freezing temperature Process compaction melting refreezing snow accumulates and becomes compact Rain in summer melts snow but the refreezes as it seeps down into snow eld Recrystalization snow that survived the summer recrystalizes and becomes more tightly packed due to pressure rn snow becomes rn which has a compact granular texture glacial ice snow and fern are pressurized and recrystalized into dense glacial ice Zone of accumulation above equilibrium line where precipitation accumulates Zone of ablation evaporation and sublimation losses below equilibrium line Equilibrium line where gains and losses equal each other Sublimation when ice turns to vapor Calving when a glacier splits and sheds to a smaller mass of ice into water How glacial ice moves brittle zone vs plastic zone regelation crevasses Brittle zone the ice on the surface of the brittle zone breaks under stress and the brittle surface breaks up into crevasses vertical cracks Plastic zone the lower part of the glacier which ows plastically as individual ice grains move relative to each other The ice grains deform to accommodate movement regelation melting under pressure and freezing again when the pressure is reduced this moves glacier from higher to lower elevation Erosion by plucking and abrasion Glacial plucking the erosion and transportation of bedrock As a glacier moves down a valley friction causes the basal ice of the glacier to melt and in ltrate joints in the bedrock Abrasion the mechanical scraping of a landscape by friction between rock and landscape during their transportation by the glacier Glacier types and locations alpine vs continental Alpine glaciers are in the mountains continental glaciers are much larger and thicker than alpine glaciers covers about 10 of the earth Ice sheets eg Greenland Antarctic Ice sheet Iceland Arctic Island Andes Alpine glaciers Cirque glaciers valley glaciers tributary glaciers piedmont glaciers tidewater glaciers Cirques smallest type forms in bowl may be origin point for larger glaciers Valley glaciers tributaries may join ow together through valleys Tributary glacier ow into a compound glacier and merge alongside one another Piedmont glaciers ice ows beyond the valley spreading out over atter land Tide water glaciers ends in sea calving to form oating pieces of ice icebergs Ice elds many alpine glaciers merged together so that there is no longer a ridge between glaciers Extends in an elongated fashion in a mountainous region Not as extensive enough to form a dome like an ice cap Ice cap An entire mountain top covered in ice roughly circular and covers an area less than 50000 kmquot2 Completely buries underlying landscape Landforms in mountains cirque arete horn col tarn U vs V shaped valley Cirques Bowls Upper portion of glacier Arete jagged sawtooth spine of rock between two glacial valleyscirques IIorn 3 cirques meet Pyramid Col Saddle pass Headward erosion of 2 cirques Reduced arete Tarns and hanging waterfalls tarns lake formed cirques Hanging waterfalls form at top of Ushaped valleys Ushaped valley glacial trough forms after a V shaped valley is lled with a glacier and when the glacier melts it forms a U Glacial deposits terminal moraine lateral moraine medial moraine till unsorted vs outwash sortedstrati ed braided rivers Terminal moraine end of farthest advance Rock debris till at end of glacier Lateral moraine rock debris till along edge of glacier Medial moraine when two glaciers with lateral moraines join Braided rivers Till unsorted moved by glacier Sediment not sorted Outwash shortedstrati ed moved by water from glacier Sediment sorted strati ed The last ice age Last Glacial Maximum 18000 years ago ice rapidly melted from about 10000 years ago know general pattern of glaciers during last ice age key features at that time eg Bering Sea land bridge between Russian and Alaska and key effects eg landscape of upper Midwest Great Lakes The last ice age was the Pleistocene Glaciation which began 24 mya and ended 10000 years ago MaXimum extent ice covered 13 of earth Sea level changes AlaskaYukon not glaciated because of lack of precipitation Left a legacy sea level lower land bridges circumboreal species Created numerous lake basins nger lakes NY and great lakes USA Missoula Flood Glacial lake Missoula 15000 years ago 500 cubic miles of water At least 40 super ood events Created washington state quotscablandsquot changed soils in the Willamette valley
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