Quizlet

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john_peter_rau : CHAP 7 - Science Review GLACIERS 7.1 ICE AGE: A period of time when much of Earth's land is covered in glaciers. 15,000 yrs. Ago 30% of land was covered in Glacial Ice Cape Cod, Long Island, Great Lakes, Fjords of Norway - Shaped by Glaciers GLACIER: Thick ice Mass that moves slowly over the land surface. • Today 10% of Earth's land area is covered with Glaciers • Originate on land in places where more snow falls each winter than melts each summer. • DYNAMIC - always moving (Few CENTIMETERS to a Few Meters daily) • AGENTS of Erosion -> Accumulate, transport, & Deposit Sediment • Snow  Recrystallizes into coarse grains ice  (Add pressure) Interlocking Crystals of glacial ice • IMP in Rock Cycle SNOWLINE: Lowest elevation in an area that remains covered in snow all year. Snow above the snowline ACCUMULATES and COMPACTS POLES: Snowline occurs at Sea Level EQUATOR: Snowline near TOP of Mnts 2 Types of GLACIERS: 1. Valley Glaciers 2. Ice Sheets VALLEY GLACIERS: • Ice masses that SLOWLY advance DOWN VALLEY'S that were originally occupied by streams. • A stream of ice that flows between steep rock walls from a place near the top of the Mtn. Valley • Can be Long OR short - Wide OR Narrow - Single or Branching w/ Tributaries ICE SHEETS: • Enormous ice masses that flow in ALL directions from ONE or MORE centers and cover EVERYTHING but the HIGHEST LAND • Aka  CONTINENTAL ICE SHEETS, b/c they cover Large Regions where Climate is VERY COLD ! • 2 Remaining Ice Sheets 1. Greenland - One sheet cover's 80% of Greenland 2. Antartic Ice Sheet - Southern Hemisphere 80% of WORLD's ICE & 2/3 of Earth's Fresh Water ( if Melted sea level rise 60-70 Meters  FLOODS would happen in coastal cities) HOW GLACIERS MOVE: FLOW: Movement of glacier - Happens in 2 ways: 1. Plastic Flow 2. Basal Slip Plastic Flow: Movement WITHIN the ICE, • Under HIGH pressure • brittle ice distorts & changes Shape (PLASTICITY) • Weight of OVERLYING ice exerts pressure on ice below causing it to FLOW. • Plastic flow begins - 50 METERS BELOW GLACIER SURFACE. • ** Top 50 Meters NOT under Pressure to have Plastic Flow. Basal Slip • Gravity makes the ice mass slip and slide downhill along the ground • Zone of Fracture: uppermost part of glacier - Brittle • Piggybacks ride on Flowing ice Below • There is Tension in zone of fracture as it moves over irregular ground (terrain). • Tension results in LARGE CRACKS  CREVASSES. • 50 Meters deep - covered by Snow Hard & Dangerous to travel across Glaciers. RATE • Different Glaciers - Different Speeds. • Some slow some fast. Alternate b/t periods of fast & periods of Slow BUDGET of Glacier • Form where more snow falls in winter than can melt during summer • Constantly gain and Lose ice. • Zone of Wastage: area of glacier BEYOND the SNOWLINE - Loses ice to MELTING ! • Calving: Large pieces of ice break off • Icebergs : when calving occurs on the water (ocean) • SLIGHTLY LESS DENSE THAN SEA WATER - they float LOW in the Water - • 10% of Mass ABOVE WATER Glacial Budget: the Balance or lack of Balance between accumulation at the upper end of a glacier and loss, or wastage at the lower end. More at the Head than melts  GLACIER ADVANCES Loses Ice faster than ice Accumulates  GLACIER RETREATS Glacier gains ice = Glacial Melting  Front (terminus) remains STATIONARY WHETER GLACIER Advances, Retreats, or Remains Stationary  ICE WITHIN GLACIER MOVES FORWARD GLACIAL EROSION: Glaciers carry Rocks Unlike streams which drop sediment as they Flow - GLACIERs hold All until it MELTS Can carry rocks as big as Buses LONG DISTANCES Many landscapes changed by the recent ICE AGE HOW: Glaceir's Erode 1. Plucking- Glacier water penetrates cracks, refreeze - expands and pries rock apart. Glacier flow over cracked bedrock, loosens it and lifts rocks incorporating them into the ice. 2. Abrasion -Glacial ice and its load of rock fragments slide over bedrock - Sandpaper to smooth & polish surface. (ROCK FLOUR - Pulverized Rock - leaves streams milky color) LARGE Fragments: leaves long scratches & Grooves gouged in bedrock Glacial Striations  Looking at them - you can tell direction of Movement • Mapping the striations over large area - Scientist can tell the ice flow GLACIAL EROSION - Variables (4 Factors) 1. Rate of glacial movement 2. Thickness of ice 3. Shape, abundance and hardness of rock fragments in the ice at the BASE of the glacier 4. Type of surface below the glacier LANDFORMS CREATEAD BY GLAC. EROSION Glaciers are responsible for a variety of erosional landscape features 1. Glacial troughs 2. Hanging valleys 3. Cirques 4. Arêtes 5. Horns GLACIAL TROUGH: before glaciations V-shaped valley - After glaciers move thru NO LONGER NARROW - Glacier Widens, Deepens, Straightens the valley into U-Shaped= GLACIAL TROUGH HANGING VALLEY: Valleys of the smaller side glaciers are left standing higher than main glacial trough-> Higher Valleys. • Rivers from hanging Valleys have SPECTACULAR WATER FALLS. ** SEE PAGE 193 - FOR LANDFORMS ** CIRQUES: A bowl shaped depression at the head of glacial valley • Surrounded on 3 sides by steep rock walls • Begin as Irregularities in the Mountainside • By Plucking Rock - Glaciers carve Cirques • Small lake at basin ARETES & HORNS • Aretes - Snaking Sharp edged ridges • Horns - sharp pyramid like peaks called horns ie: Matterhorn GLACIAL DEPOSITS Rocky fields in New England, wheat fields in Dakota plains, Rolling Midwest Farms - rocky landscapes resulting from glacial deposits TYPES of GLACIAL DRIFT - applies to all sediments of glacial origin, no matter HOW deposited 1. Till - Material deposited directly by glacier as it melts - NO SORTING fragments MIXED 2. Stratified Drift - Sediment laid down by glacial MELTWATER. SORTED by Size & Weight • Made by streams coming from glacier • Mostly made of Sand & Gravel (can't move Lg. boulders - finer sediment carried by GLA.) GLACIAL ERRATICS - boulders found free lying or in till • Mineral content DIFFERENT from underlying bedrock (ground) - that's why we know they were carried from somewhere else • Geologist determine path of long gone glaciers by studying the mineral GLACIAL ERRATICS MORAINES, OUTWASHES PLAINS & KETTLES Glaciers are responsible for variety of depositional features 1. Moraines - ridges of till that glaciers leave when they melt • Lateral Moraines - Ridges that form along the sides of glacial valleys when the glacier melts & leaves the material it gathered. • Medial Moraines - Formed when 2 valley glaciers join to form a single ice stream - till that was carried along the edges of each glacier join to from DARK STRIPE within the glacier • End Moraine - Ridge that is formed as ice melts and deposited debris ** LONGER GLA. STATIONARY - LARGER END MORAINE GROWS ** • Ground Moraine - Form when glacier RECEDES - continues to deposit DEBRIS - Instead of a ridge it creates a rock strewn gently ROLLING PLAIN. Fills in LOW SPOTS and CLOG Stream Channels. SWAMP LAND. • Terminal Moraine - The FARTHEST END MORAINE • Recessional End Moraine - forms when ice is stationary during its retreat END MORAINE examples: Long Island & Cape Cod, Martha's Vineyard, & Nantucket 2. Outwash plains - Sediment ramp resulting from ice sheet melt - MILKY (Forms SAME TIME END MORAINE IS BEING FORMED) 3. Kettles - depressions and small lakes in the end moraines and Outwash plains WALDEN POND 4. Drumlins - streamlined hills composed of till Tall Steep one end smaller other end 15 - 6- Meters > l Kilometer long 5. Eskers - Snake like ridges composed of Sand & Gravel deposited by streams in a tunnel BELOW GLACIER ** EVEN THOUGH A GLACIER IS STATIONARY - ICE STILL FLOWS ICE AGE NORTHERN HEMISPHERE was covered w/more ICE than the Southern Hemisphere b/c southern Hem. Had FAR LESS land and glaciers were confined to ANTARTICA - They couldn't move ICE AGE - Began 2 -3 Million Years ago Pleistocene Epoch Great Lakes were swamp land and then were carved out to be DEEP great lakes DESERTS Weathering- weathered debris in deserts result from MECHANICAL WEATHERING (Mineral content Unchanged) Rock weathering is REDUCED in desert b/c of 1. No Moisture 2. No Organic Acid from dying plants CHEMICAL WEATHERING - NOT completely absent. - over a long time, clays and thin soils do form EPHEMERAL STREAM - stream that ONLY carry water AFTER a rain (Washes or ARROYOS) Flash floods - soil cannot absorb it - Heavy rains - LOT OF EROSION DURING FLASH FLOOD INTERIOR DRAINAGE - intermittent streams that do NOT flow out of the desert to the OCEAN ALLUVIAL FAN: a Cone of debris at the MOUTH of the Canyon. LOW VELOCITY - dump load Playa Lake - A stream that flows across an Alluvial Fan to the center of the basin converting the basin floor to a PLAYA LAKE. • Last a few days or few weeksm EVAPORATION or INFILTRATION • PLAYA - dry, flat lake bed that REMAINS MOST desert streams dry up long before they ever reach the ocean. (Interior Drainage) The Streams are quickly depleted by EVAPORATION and SOIL INFILTRATION. Colorado & Nile Rivers - Permanent streams - rivers that do manage to cross arid regions MOST Desert EROSION results from RUNNING WATER not wind Desertification: changing of good land to desert - due to inappropriate LAND USE WIND EROSION • Humid areas can resist wind erosion - moisture BINDS soil particles (MUD) & Plants anchor • Desert - Less humidity and Less Plants • 1930's - Severe Drought - DUST BOWL - swept away the fertile topsoil. • Deflation lowered the land by a Meter or more WIND ERODES 2 WAYS: 1. Deflation - Lifting and removal of loose particles such as clay and silt. • Saltation - Coarser sand roll or skip along the surface. BED LOAD - large particles of sand make up this • Blowouts - shallow depressions caused by Deflation (in GREAT PLAINS) • Desert pavement - a layer of coarse pebbles and cobbles too lg to move by wind Which is left when silt and sand are blown away 2. Abrasion - happens when wind blown sand cuts and polishes exposed rock surfaces Blowing sand grinds boulders & rocks Sandblasting WIND DEPOSITS - can create land forms when it deposits its sediments especially in deserts and along coasts. Layers of Loess Sand Dunes - Features of deposited WIND LOESS - windblown silt that blankets the landscape. (deposits in LAYERS) • Western & Northern China - thickest & Most extensive deposits SAND DUNES • Like water, wind releases its load of sediments when VELOCITY FALLS • Sand accumulates when OBSTRUCTION crosses its path & slows MOVEMENT • DEPOSITS in Mounds or Ridges called DUNES. Dunes forms: Obstruction, sand particle fall to ground, once it mounds up, obstruction is larger, gathers more sand - eventually it is a DUNE. STEEPER on SHELTERED SIDE GENTLY SLOPING on SIDE FACING THE WIND SHELTERED SIDE of DUNE - it forms layers inclined in the direction the wind is blowing Cross Beds - Sloping layers inclinded in the direction the wind is blowing TYPES OF DUNES FORM depends on the 1. wind direction and speed 2. how much sand available 3. amount of vegetation BARCHAN DUNES: • Solitary • Cresent Shaped • Form on FLAT / HARD ground where sand and vegetation limited • Symmetrical - 30 Meters TRANSVERSE DUNES: • Steady WINDS, • LOTS OF SAND - NO Vegetation or SPARSE • Long ridges - PERPENDICULAR to wind direction • Coastal Areas • 200 METERS High - 1-3 Kilometers across - • In the SAND SEAS = Sahara & Arabian Desert BARCHANOID DUNES: • Intermediate b/t barchans and transverse • Scalloped rows RIGHT ANGLES to the WIND • Rows resemble series of Barchans side by side • White Sands New Mexico LONGITUDINAL DUNES: • Long ridges of sand PARALLEL to Wind • Sand supply Moderate • Wind direction VARIES • 100 M High and 100 Kilometers long PARABOLIC DUNES • Backward Barchans • Tips point INTO the wind instead of away • Form where VEGETATION covers sand • Found on COAST - strong ONSHORE winds • LOTS OF sand STAR DUNES: • Isolated hills of sand • Found in SAHARA & ARABIAN DESERT • Bases resemble STARS • 3-4 Sharp ridges - meet in the middle • Variable wind - 90 Meters CHAP 20 - Weather Patterns and Severe Storms Hurricanes - Tropical oceans Late summer / early Fall Tornadoes - Over land Spring / Summer Summer Heat waves- High Temps, High humidity often end w/ a storm moving thru Cold Spell - Frigid temps and clear skies followed by cloudy snowy warm days What causes the changes ? Air Masses - an immense body of air that is characterized by similar temps and amounts of moisture at any give altitude. • Because of its size it can take several days to move over an area. • Results in constant weather for few days  Air Mass Weather Movement of air masses - when an air mass moves out it carries its temps and moisture w/ it. • As it moves the characteristics of an air mass change and so does the weather I the area over which the air mass moves. • Cold air moves down from Canada  warms as it moves South but still brings cold temp. CLASSIFYING AIR MASSES Air masses are classified by the region OVER WHICH THEY FORM SOURCE REGION: area over which an air mass gets its char. Properties of temp & moisture 1. Polar: Form at high latitudes Earth's poles (COLD) 2. Tropical: Form at LOW latitudes (WARM) 3. Continental: Air masses form over LAND MORE DRY 4. Maritime: Air masses form over SEA - MORE HUMID (MIX AND MATCH THE ABOVE - See pg. 560) N. AM. Weather: East of the Rockies -  CONTINENTAL POLARS and MARITIME TROPICAL • Canada, Alaska, Artic Gulf of Mexico, Caribbean Sea, Atlantic Ocean 1. CONTINENTAL POLAR AIR MASSSESS - Cold and Dry in winter or Cool and Dry in the Summer Do NOT bring lots of PRECIPITATION EXCEPT - Leeward side of the GREAT LAKES !! LAKE EFFECT SNOW - Difference in the temp bt the lakes and land is LARGE. Especially when a cold air mass is pushing thru. Heat and Moisture from the warm lake surface - by the time it reaches leeward side air mass in HUMID and UNSTABLE - HEAVY SNOW -- SOUTH BEND !! 2. MARITIME TROPICAL AIR MASSES - Warm loaded with moisture UNSTABLE. Most of the precip in Eastern 2/3 of the US. • High Temps and Oppressively humid 3. MARITIME POLAR AIR MASSES - A. Winter; Come from the N. Pacific (SIBERIA) o Start as Cold dry air mass often CHANGE into mild, HUMID UNSTABLE maritime polar during its journey across the N. Pacific. o Has LOW clouds and SHOWERS o Heavy rain or snow on WINWARD slopes of Mnts. B. Come from N. Atlantic (CANADA - East Coast) o Influences weather in the North East (NY, NJ -New England) o Passing Low Pressure here is called a Nor'easter (Winter Hurricane) o 4. CONTINENTAL TROPICAL AIR MASSES - LEAST influence on the N. Am Weather HOT DRY AIR - begin in SW US and Mexico in the summer OCCASIONALLY do cT air masses affect the weather outside their source Region When it moves causes Extremely HOT, DROUGHT like in the GREAT PLAINS (summer) (Fall)  Mild weather in the Great Lakes (INDIAN SUMMER)Unconditionally warm MILD FORMATION OF FRONTS Air masses have Diff. temps and Moisture depending on the Source of the Region FRONT: WHEN 2 air masses meet, they form a front which is a boundary that separates two air masses of different properties. • Form between any 2 contrasting air masses. • Fronts are NARROW (compared to large air masses) 15 -200 km WIDE • WARM LESS DENSE AIR overlies the COOLER DENSER AIR TYPES OF FRONTS 1. Warm Front 2. Cold Front 3. Stationary Front 4. Occluded Front Warm Front: Forms when warm air moves into an area formerly covered by COOLER AIR • Slope of Warm Front is GRADUAL Slow Movement • Warm air RISES and COOLS  Produces Clouds and PRECIPITATION • First Sign of approaching WARM front  CIRRUS CLOUDS then change to CIRRO STRATUS then comes snow and rain • Light to Mod precip over a LARGE Area • Gradual increase in TEMP occurs w/ passage • Wind shift form E to SW Cold Front: forms when Cold, Dense air moves into a region occupied by warmer air. • As Front moves it becomes STEEPER • Cold Fronts are TWICE as steep as warm Fronts • Advance MORE rapidly • RATE OF MOVEMENT & STEEPNESS OF SLOPE  account for the VIOLENT WEATHER • Lifting air leads to Heavy downpours and GUSTY winds TOWERING CLOUDS • Temps DROP- weather clears soon after front passes Stationary Front- When air on either side of a front is neither toward the cold air mass nor toward the war air mass - but PARALLEL to the line of the front • Surface Position does NOT move Occluded Fronts: When a cold front overtakes a warm front this forms • Advancing cold air wedges the warm front upward • COMPLEX weather - PRECIPITATION MIDDLE LATITUDE CYLONES • Large centers of LOW Pressure travel front WEST to EAST • STORMY WEATHER • COUNTER CLOCK WISE • Warm front AND Cold Front • Forceful lifting causes clouds with ABUNDANT PRECIP HOW THEY FORM Stage I - Development of Stationary Front , 2 Air masses w/Diff temps moving in opposite directions Takes on a wave shape Warm air moves toward the poles - invades colder air. Cold air moving towards Equator - Changes in air pressure COUNTER CLOCKWISE AIRFLOW. Cold fronts advance QUICKLY and lifts warm front—Process is called OCCLUSION. As Occlusion happens Storm gets STRONGER. Pressure at center FALLS and WIND speeds INCREASE. In the Winter Heavy snowfall BLIZZARDS. As warm air rises, pressure change weakens. In a day or 2 the entire warm are is displaced Temp differences are gone - Energy is exhausted Flow fades AWAY. ** SEE PAGE 569 ** ROLE OF AIRFLOW ALOFT Middle Lat. Cyclones  Air High UP in the Atmos. Fuels a Mid Lat Cyclone. AIR ALOFT - Imp. Role in maintaining clyclonic and ANTI cyclonic circulation. CLYCLONES: Surface air that feeds cyclone is from air flowing OUT of an ANTIcycl. ANTICYCLONES: FOUND next to a cyclone - Depends on the air HIGH in the Atmos to maintain circulation • Air spreading our at the surface is balanced by air coming together HIGH UP THUNDER STORMS • Storm that generates lightning and thunder; produce gusty winds, heavy rain and HAIL. • Single Cumulonimbus Cloud and influence ONE area • Cluster of Cumulonimbus and stretch for miles along Cold front OCCURRENCE of THUNDERSTORMS • 2000 storms in progress on Earth • Occurs mostly in the TROPICS - warm moist air • 45,000 storms EACH DAY • 16 Million - ANUALLY • Florida and Gulf Coast • Western have FEW bc warm moist unstable maritime tropical air goes there. THUNDERSTORM DEVELOPMENT • Form when warm humid air rises in an UNSTABLE environ. • Life span 1-2 HOURS • 3 Stages: 1. Cumulus Stage - Strong Updrafts supply MOIST AIR. Blasts of air rises higher than last causes cloud to grow VERTICALLY. Within a HOUR go to 2. Mature Stage - The amt. and size of precip is too great for the updrafts to SUPPORT so they FALL • MOST ACTIVE stage - Gusty winds, lightning, heavy showers hail 3. Final Stage - (DISSIPATION Stage) Downdrafts dominate now; COOLing Effect TORNADOES Violent windstorms that take the form of a rotating column of air called a VORTEX. Vortex extends downward from a cumulonimbus cloud all the way to the GROUND. - Single vortex - but in STRONGER tornadoes SMALLER vortexes rotate too - 10 Mdiameter and rotate MORE rapidly. - Smaller vortexes - EXPLAINS tornado damage where one building is destroyed and another is Standing. OCCURRENCE and DEVELOPMENT • 770 tornadoes reported each year. • Occur ANYTIME during the year MOSTLY April - June (Dec and Jan LESS LIKELY) • Form in Assoc. with Severe THUNDERSTORMS Begins as a Mesocyclone- Vertical cylinder of rotating air that develops in UPDRAFT of thunderstorms • Stong winds HIGH up cause lower winds in Atmos to ROLL - Rolling air then TILTS and eventually become VERTICAL (Doesn't ALWAYS mean tornado will follow) Intensity • Pressure inside tornado - 10% LOWER than pressure OUTSIDE storm • LOW pressure in tornado causes air near ground to RUSH into tornado from ALL directions. Eventually air merges with air flow of CUMULOnimbus cloud that formed storm. • B/C of pressure changes max winds approach 480 Kilometers/Hr • FUJITA tornado intensity scale. - Determined by Assessing DAMAGE ( too hard to measure wind) P 574 -> CHECK it out !! Hurricanes • Whirling Tropical cyclones that produce sustained winds of at least 119 Kilometer/HR in US • AKA Typhoons, cyclones, tropical cyclones • MOST powerful storms on EARTH - Can make 15 M waves at sea that are capable of destruction HUNDREDS of miles away. • Hits land - Strong winds and extensive flooding can cause LOTS of damage • Hurricanes are becoming growing threat because MORE people are LIVING and WORKING near COASTS • Once storms reach TROPICAL STORM Status it gets a Name - Names are given to prevent confusion when the storms are described and when discussed in the future OCCURRENCE of Hurricanes • Form bt 5 - 20 Degrees NORTH and SOUTH LATITUDE (Equator) • North Pacific - GREATEST # of Hurricanes 20 /yr • Coast SOUTH & EAST - Fewer than 5 / yr • 199 kilometers / HR  HURRICANE STATUS DEVELOPMENT • Heat engine fueled by NRG given off when huge quantities of water vapor CONDENSE • Develop MOST often in the LATE SUMMER when water temp are WARM enough to provide the necessary heat and moisture to the air. • Tropical disturbance - little or no Rotation • INWARD rush of warm AIR MOVES toward CORE • AIR TURNS upward and rises - makes DOUGHNUT SHAPE  EYE WALL • Heaviest Rain - Greatest Wind  Eye Wall • CENTER  EYE - Precip NONE & WIND NONE (Warmest PART of the STORM) INTENSITY • SAFFIR -SIMPSON SCALE Category 1 - 5 PG 577 • STORM SURGES - Most damage; Water dome 65-80 km high sweeps across coast where eye make land fall. • Weaken if moves over COOL ocean water cannot supply fuel (warm & Moist) • Weakens when moves over land - o NOT sufficient MOISTURE o FRICTION w/land •