global environment chapter 15: eolian processes and arid landscapes

largest dunes

star dunes

The motion of _________ _______ slides and rolls particles too large for saltation.

surface creep

eolian processes transport dust, silt, and sand by ___________

suspension, saltation, and surface creep.

In the U.S. interior west, the _________ is known for its north-and-south-trending basins and mountains

the Basin and Range Province

badlands are another example of _________

the erosive work of water in arid and semiarid regions

only_________ travel significant distances

the finest dust particles

deflation

the process by which wind removes surface materials

barchan dunes form ___________

usually in areas with limited sand supply and little or no vegetation

Rocks that bear evidence of eolian abrasion

ventifacts

How are ventifacts and yardangs formed by wind processes?

ventifacts: -pitted, fluted, grooved, polished from erosion -direction determined by consistent flow of airborne particles in winds yardangs: -larger scale -deflation + abrasion -abrasion on windward, deflation on leeward

List some landforms unique to arid regions and explain their formation.

*alluvial fans *bajada *playa *badlands *basin and range province *mesa *butte *inselberg

Discuss eolian erosion and the resultant landforms.

*deflation -deflation hallows -blowouts *abrasion *ventifacts *yardangs *desert pavement

Discuss the causes and consequences of desertification.

*desertification

Explain the formation of sand dunes and describe loess deposits and their origins.

*dunes *erg -sand sea -slipface -crescentic -linear -star *barchan dunes *star dunes *loess

Describe eolian transport of dust and sand.

*eolian *surface creep

What processes are involved in the formation of an alluvial fan?

-flowing water (like flash flood) loses velocity as it leaves a canyon -stream drops sediment layers on base of mountain block -water flows over surface of fan -> braided channel

What is the arrangement, or sorting, of alluvial material on the fan?

-naturally sorted by size -coarsest materials: near mouth of canyon/apex of fan -finest clays carried in suspension + solution all the way to valley floor

Explain the concept of surface creep.

-particles larger than 0.5mm (too large for saltation) slide along ground -can collide w/saltating particles, knocking them loose -mechanism for wind transport

an example of aligned pairs of normal faults and a distinctive horst-and-graben landscape

Basin and Range Province region

desertification

Degradation of land, especially in semiarid areas, primarily because of human actions like excessive crop planting, animal grazing, and tree cutting.

__________ crash into other particles, knocking them both loose and forward.

Saltating particles

surface creep

Sediment transport in which the wind causes particles to roll along the ground.

abrasion

The grinding away of rock by other rock particles carried in water, ice, or wind

badlands

Wasteland that has been carved into unusual shapes by wind and water

As the height of the sand pile increases above 30 cm (12 in.) _____________

a steeply sloping *slipface* on the lee side and characteristic dune features are formed

yardang

a streamlined rock structure formed by deflation and abrasion; appears elongated and aligned with the most effective wind direction

ventifact

any rock that is pitted, grooved, or polished by wind abrasion

rugged terrain of slopes dissected by rills and gullies

badlands

A ______ may form where individual alluvial fans coalesce along a mountain block.

bajada

form with their tips pointing downwind

barchan dunes

low-elevation areas that dip downward toward the center

basins

smaller, steep-sided landforms that form from the weathering and mass wasting of mesas

buttes

Wind, or _________, processes transport dust, silt, and sand by supension, saltation, and surface creep.

eolian

What is the difference between eolian saltation and fluvial saltation?

eolian saltation: -fine grain sand bounces + skips -wind transport -only works for dry surface material fluvial saltation: -river/water transport

An extensive area of dunes, such as that found in North Africa

erg or sand sea

What is the role of chemical weathering processes in arid environments?

ex] desert varnish/rock varnish -thin, dark coating of clay + iron + manganese -> metabolized by microbes -> oxide minerals ex] cave/side of cave drawings

erg

extensive area of sand and dunes

mesa

flat-topped landforms with steep slopes on all sides, elevated above surrounding landscape

What is the origin of loess in the Palouse?

glacial sources

star dunes are formed __________

in areas with shifting wind directions

an isolated remnant formed of resistant rock, a product of weathering and erosion

inselberg

With water diversions for agriculture and development ___________

lakes are shrinking

The finer material suspended in a dust storm is __________ than are the coarser particles of a sandstorm

lifted much higher

Windblown ________ consists of fine-grained clays and silts that are moved long distances by wind and are redeposited as an unstratified, homogeneous blanket of material

loess

Together, these features form the ____________ ________ seen in parts of Arizona and Utah

mesa-and-butte topography

flat landforms with steep slopes on all sides that are elevated above the surrounding landscape

mesas

Differential erosion can produce ________ and _____

mesas, buttes

Describe two landforms associated with basin and range topography.

mountains + valleys ex] Death Valley, CA

In other regions, _____ ______ resources has combined with ________ to cause desertification

overexploitation of water, drought

In some drylands, ___________ is a primary cause of desertification, often in combination with socioeconomic factors.

overgrazing

Runoff may flow all the way to the valley floor where it forms a _________

playa

a low, intermittently wet area in a region of internal drainage

playa

interconnected mountains of varying elevations above the basins

ranges

lakes are shrinking, leaving _________ and ________ that is moved by ______ across the landscape.

salt and dust, wind

deflation hollows, or blowouts ranging in size from _________

small indentations less than a meter wide up to areas hundreds of meters wide and many meters deep.

overgrazing is a primary cause of desertification often in combination with ___________

socioeconomic factors.

desertification currently affects ___________

some 1.5 billion people

Describe and explain the recent changes at Lake Urmia in Iran.

-vanishing lake -> worsening desertification -decreased 88% since 1970s -shrinking even during times of enough rain -water withdrawals for agri + development = main cause -shallow water -> shoreline covered in salt deposits -increased salinity -> not safe for brine shrimp -> no food for migratory birds

basin and range province

A broad, Cenozoic continental rift that has affected a portion of the western United States in Nevada, Utah, and Arizona; in this province, tilted fault blocks form ranges, and alluvium-filled valleys are basins.

butte

A flat topped rock or hill formation with steep sides. related: mesa

dune

A hill or ridge of sand piled up by the wind

desert pavement

A layer of coarse pebbles and gravel created when wind removed the finer material. related: deflation, sheetflow

barchan dune

A solitary sand dune shaped like a crescent with its tips pointing downwind.

alluvial fan

A wide, sloping deposit of sediment formed where a stream leaves a mountain range related: bajada

loess

A wind-formed deposit made of fine particles of clay and silt

bajada

An apron of sediment along a mountain front created by the coalescence of alluvial fans. related: alluvial fan

star dune

An isolated hill of sand that exhibits a complex form and develops where wind directions are variable.

the "sandblasting" of rock surfaces with particles captured in the air

abrasion

Along mountain fronts in drylands, _______ ______ develop where ephemeral stream channels exit from canyons into the valley below.

alluvial fans

What world regions are affected by desertification?

along margins of semiarid + arid lands -worldwide -covers 1.9 billion hectares + affect 1.5 billion people -more land each year

inselberg

an isolated mountain

playa

area of salt crust left behind by evaporation on desert floor

What are the main causes and consequences of desertification?

causes: -poor agricultural practices (overgrazing, abusing soil structure + fertility) -improper soil-moisture management -salinization + nutrient depletion -deforestation -climate change consequences: -expansion of deserts -less rainfall -deterioration of vegetation + soils -Loss of biodiversity -Food insecurity due to crop failure or reduced yields -loss of vegetation cover and therefore of food for livestock and humans -Increased risk of zoonotic diseases, such as COVID-19

Dune forms are broadly classified as_________

crescentic, linear, and star

Erosion of the ground surface from the lifting and removal of particles by wind

deflation

Wherever wind encounters loose sediment, deflation may remove enough material to form depressions

deflation hollows, or blowouts

eolian

deposited by wind

name for the hard, stony surface that forms in some deserts and protects underlying sediment from erosion.

desert pavement

The ongoing degradation of drylands caused by human activities and climate change

desertification

When saltating sand grains encounter small patches of sand, kinetic energy is _________, and the grains start to _____________

dissipated, build into a dune

Wind exerts a __________ on surface particles until they become airborne

drag or frictional pull

wind-sculpted accumulations of sand that form in arid and semiarid climates and along some coastlines where sand is available

dunes

What is deflation and what role does it have in the formation of desert pavement?

what is it: erosion of ground surface from lifting + removal of individual particles by wind desert pavement: hard stony surface (not usual sand) role: wind removes fine particles -> leaving larger pebbles, gravels, + rocks -> consolidated desert pavement

Where does the sediment that forms the loess deposits of China come from?

windblown desert sediment

These windblown deposits occur _______ and can develop into _____ ______ ______

worldwide, good agricultural soils

deflation and abrasion are capable of streamlining rock structures, leaving behind distinctive rock formations or elongated ridges

yardangs