Geography - Test 4

Kupfer

Aeolian geomorphology

wind as a geomorphic agent

what are the two processes of aeolian erosion

deflation and abrasion

deflation

erosion of particles as wind picks them up and moves them

abrasion

erosion by windblown particles

wind speed

higher winds means more erosion

surface cover and roughness

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

soil texture and cloddiness

affects cohesion and erodibility of soils

soil moisture

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

fetch

distance the wind blows without encountering a barrier

desert pavement

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

what does abrasion lead to

smoothing or pitting of surfaces

ventifact

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

mushroom rocks

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

yardangs

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.

what does distance and height of transport depend on

wind velocity and particle size

where is transported material deposited

where wind velocity decreases

What are the various types of dunes

barchans, transverse, seifs, parabolic, star

what is another word for a barchan dune

crescentic

what is another word for a seif dune

longitudinal dune

what is another word for a parabolic dune

blowout

what is loess

windblown silt

Dunes can move while maintaining a constant shape

TRUE or FALSE

TRUE

sand dune

wind sculpted accumulation of sand

sand dunes form where

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

barchans

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

transverse dunes

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

longitudinal dunes

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

What type of dune is associated with bidirectional winds

longitudinal dunes are

parabolic dunes

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

star dunes

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

what occurs where winds shift and there is no prevailing wind direction

star dunes do

loess

wind deposited blankets of silt and clay

What did loess originate as

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

bluffs or cliffs and pillars form

due to vertical jointing

high drainage density is due to

high erodibility of loess

What are extrabasin transfers of fine material important to

explaining local soil chemistry and nutrient budgets

reg

stony depressions and flats

hamada

high barren rocky plateaus

when sands, silts, and clays are carried away what happens

they leave a coarse surface deposit of pebbles and stones

erg

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

what is an erg

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

dune fields

smaller ergs

Are ergs erosional or depositional

depositional

regs are a

depression with desert pavement

dry rivers are called

washes or arroyos

mesas

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

buttes

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

what is another word for a pinnacle

needle

pinnacle

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

alluvial fan

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

bajada

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

playa

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

salt flat

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

pluvial lakes

formed by higher rainfall and or lower evaporation under past climates

geological, climatological and biological proxies (natural archives) indicators or phenomena used to infer past conditions like

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

drivers of change

1. factors that change geography
2. factors that change global climates

factors that change geography

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

factors that change global climates

1. atmospheric composition
2. milankovich cycles and feedbacks

natural climatic variability

naturally occurring factors that affect global temperatures

What are some 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

sun spots

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

greenhouse effect

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

What has happened throughout Earths history pertaining greenhouse gas concentrations

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

What do gases injected into the upper atmosphere reflect

incoming solar radiation back to space, causing cooling

Milankovick Cycles

1. eccentricity
2. obliquity
3. precession

eccentricity

ellipticity of the earths orbit

obliquity

tilt of the earths axis: 22.1 degrees - 24.5 degrees

precession

orientation of the earths axis

Milankovich cycles interact with feedbacks in

1. albedo
2. concentrations of greenhouse gases
3. oceanic circulation

Eustatic sea level changes

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

glacier

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

as now accumulates it is compressed, becoming more dense and forming

neve

alpine glaciers

located in mountains; largely confined to areas within valley walls

continental ice sheets

large, unconfined glaciers that cover continental areas

accumulation

new inputs of snow

ablation

losses of ice

mass balance

accumulation - ablation

internal plastic flow

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

near the surface of the glacier, the ice is more brittle and cracks, forming

crevasses

zone of accumulation

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

zone of ablation

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

plucking

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

abrasion

plucked debris grinds across bedrock, scouring away material

What two ways can material be transported

1. by meltwater streams running through and out of a glacier
2. by the ice within or on top of a glacier

deposition by meltwater streams running through and out of a glacier

glaciofluvial deposits, valley train

by the ice

till, moraines

valley train deposit

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

Till

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

moraine

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

cirque

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

horn

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

arete

a sharp ridge dividing two cirques or glacial valleys

tarn

a small glacial lake

U shaped glacial valley

glaciated valley that takes on the shape of a U

hanging valley

valleys of tributaries left stranded high above a glaciated valley floor

paternoster lakes

small stair stepped lakes running down a glaciated valley

fjord

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