Geography - Test 4

wind as a geomorphic agent

deflation and abrasion

erosion of particles as wind picks them up and moves them

erosion by windblown particles

higher winds means more erosion

alter wind speed by absorbing and deflecting part of the wind energy away from erodible soil

affects cohesion and erodibility of soils

moist soil is more cohesive and thus experiences less wind based erosion than dry soil

distance the wind blows without encountering a barrier

removal of find particles by wind and surface flow leaves a surface of larger stones

smoothing or pitting of surfaces

a rock that has been abraded, pitted, etched, grooved, or polished by wind-driven sand

near the base, the material carrying capacity of the wind is at its max, so abrasion is maximized. In some cases, the presence of harder rock strata above a softer rock contributes as well

form where winds are strong, unidirectional, and carry an abrasive sediment load. The wind cuts down low-lying areas into parallel ridges which gradually erode into separate hills.

wind velocity and particle size

where wind velocity decreases

barchans, transverse, seifs, parabolic, star

crescentic

longitudinal dune

blowout

windblown silt

TRUE

wind sculpted accumulation of sand

1. there is a plentiful supply of sand

2. there is little surface protection and cohesion

3. a natural trap causes the wind to drop the sand

crescent shaped dunes with horns pointing downwind from the dominant wind direction

barchans can become aligned together along a plane perpendicular to the wind. If the line becomes somewhat straight, the resulting dune ridges form these

long, straight sharp crested dunes with two slip faces that are aligned parallel to the wind direction

longitudinal dunes are

formed from blowouts where the erosion of vegetated sand leads to a U shaped depression. the elongated arms, which are located on the upwind side, are often held in place by vegetation

pyramidal dunes with slipfaces on three or more arms that radiate from the high center of the mound

star dunes do

wind deposited blankets of silt and clay

silt ground up and deposited by glaciers during ice ages. it was then picked up and deposited farther east by wind, forming blankets of silt

due to vertical jointing

high erodibility of loess

explaining local soil chemistry and nutrient budgets

stony depressions and flats

high barren rocky plateaus

they leave a coarse surface deposit of pebbles and stones

broad, sand seas covered with wind swept sand with little or no plant cover

a desert area that contains more than 48 square miles of aeolian sand and where sand covers more than 20% of the surface

smaller ergs

depositional

depression with desert pavement

washes or arroyos

tablelands/plateaus with a flat top and sides that are usually steep cliffs

isolated hills with steep, often vertical sides and a small, relatively flat top

needle

an individual column of rock, isolated from other rocks or groups of rocks, in the shape of a vertical shaft or spire

when water flows out of mountains onto the desert floor, it slows down and deposits material forming a fan shaped feature similar to a delta

merging of alluvial fans creates a ramp or apron of material at the base of slopes

a usually dry lakebed underlain by fine sediment or salts deposited by shallow lake waters on the floor of a closed basin

a flat expanse of ground covered with salt and other minerals formed where water pools and evaporates

formed by higher rainfall and or lower evaporation under past climates

fossils, geological deposits, pollen, tree rings, corals, ice cores

1. factors that change geography

2. factors that change global climates

plate tectonics alters latitudes of landmasses, reshapes topography, and changes currents

1. atmospheric composition

2. milankovich cycles and feedbacks

naturally occurring factors that affect global temperatures

1. variations in solar output

2. factors affecting how solar energy is received, reflected, absorbed, and stored

   • atmospheric composition

   • milankovich cycles and feedbacks

regions of reduced solar temperatures caused by variations in the suns magnetic field. These have a roughly 11 year cycle

heat is trapped in the lower atmosphere by certain gases that allow shortwave, incoming sunlight to pass but absorb longer wave outgoing energy from the planets surface

they have varied naturally which has contributed to changes in earths climate

incoming solar radiation back to space, causing cooling

1. eccentricity

2. obliquity

3. precession

ellipticity of the earths orbit

tilt of the earths axis: 22.1 degrees - 24.5 degrees

orientation of the earths axis

1. albedo

2. concentrations of greenhouse gases

3. oceanic circulation

changes in glacial extent during the quaternary have also led to changes in sea level related to the freezing or melting of great masses of ice

large mass of perennial ice formed by the accumulation and recrystallization of snow under pressure

neve

located in mountains; largely confined to areas within valley walls

large, unconfined glaciers that cover continental areas

new inputs of snow

losses of ice

accumulation - ablation

weight of the overlying glacier causes glacial ice to move like a slow moving plastic river

crevasses

snow input is higher than melt; net accumulation feeds ice flow downslope

snow input is less than melt; melting more rapid than accumulation so relies on ice flows above

rocks are loosened, detached and carried away by the glaciers movement

plucked debris grinds across bedrock, scouring away material

1. by meltwater streams running through and out of a glacier

2. by the ice within or on top of a glacier

glaciofluvial deposits, valley train

till, moraines

glacially eroded material that is deposited by meltwater streams beyond the furthest extent of glaciation

blanket of eroded material all sizes that is dropped as a glacier retreats

ridge of unsorted glacial material piled up at the edge of a glacier by internal plastic flow

a scooped out bowl shaped basin at the head of an alpine glacier

a pyramidal peak that results when several glaciers create cirques on various sides of a mountain

a sharp ridge dividing two cirques or glacial valleys

a small glacial lake

glaciated valley that takes on the shape of a U

valleys of tributaries left stranded high above a glaciated valley floor

small stair stepped lakes running down a glaciated valley

a long, deep, narrow sea inlet formed by submergence of a glaciated valley formed by eustatic sea level rise