landforms of mid- and low-latitude deserts

Question 1

types of mechanical weathering

Answer 1

insolation, exfoliation, salt, freeze-thaw

Question 2

types of chemical weathering

Answer 2

hydration, oxidation, solution

Question 3

Insolation weathering

Answer 3

high temp ranges (from 80C at day to under freezing at night) cause expansion and contracting rocks causing disintegration

Question 4

exfoliation or onion skin

Answer 4

as weathering occurs pressure is released from rocks at depth, cracks form parallel to rock surface, capillary action brings salts to surface, salts deposited in cracks and enhanced chemical weathering peel rock from surface

Question 5

salt weathering

Answer 5

water in joints evaporates leaving salts, crystals grow making pressure

Question 6

freeze-thaw weathering

Answer 6

heat loss at night makes water in joints freeze and expand, causes gradual rock break up

Question 7

hydration weathering

Answer 7

absorption of minimal moisture causes rocks to swell and makes them vulnerable

Question 8

oxidation weathering

Answer 8

oxygen in water reacts with minerals, making them expand, weakening rocks

Question 9

solution weathering

Answer 9

some minerals dissolve in slightly acidic water and causes rock disintegration

Question 10

biological weathering

Answer 10

sparse veg in deserts limits this, however trees and shrub root systems can widen joints and dislodge small particles

Question 11

debris flow (mass movement)

Answer 11

large amount of rock fragments, mud and soil move downslope at speed after heavy rain where veg is sparse

Question 12

rockfalls and rock slides (mass movement)

Answer 12

resistant rock rests on weaker rock, undercutting at base of slope can be destabilising

Question 13

aeolian transport processes

Answer 13

creep, saltation (confined under 2m above surface) and suspension

Question 14

aeolian erosion processes

Answer 14

deflation: removal of fine particles, corrasion: wind blown sand against rocks, attrition: particles carried by wind become smaller and rounder hitting each other

Question 15

aeolian deposition

Answer 15

as wind energy declines, deposition occurs forming sand seas or ergs in the sahara

Question 16

wadis

Answer 16

steep sides, wide bottomed, gorge-like valleys, formed by fluvial erosion, rarely filled with water, sediment build up on valley floor, either always dry or ephemeral streams that are fast and result of intense storms

Question 17

canyons

Answer 17

narrow river valleys with near vertical sides, caused by fluvial erosion, vertical erosion mostly since solid rock walls allow little sideways movement of river channels

Question 18

zeugen

Answer 18

collective term for pedestal rocks, rock pillars and yardangs. Undercutting where less resistant rock lies under more resistant rock. Created by sand grains in aeolian erosion and moisture in weathering

Question 19

pedestal rocks

Answer 19

mushroom shaped rocks within zeugen group

Question 20

yardangs

Answer 20

streamlined parallel ridges of rock, aligned in prevailing wind direction, within zeugen group

Question 21

ventifacts

Answer 21

rocks on desert surface shaped by abrasion of wind blown sand

Question 22

desert pavements

Answer 22

fine material is removed and coarse material and pebbles left behind

Question 23

dune formation

Answer 23

adequate sand supply, strong and frequent wind, and an obstacle to trap the sand. sand accumulates on peak and small avalanche occurs on slip face

Question 24

barchan dunes

Answer 24

two horns facing downwind, where wind is predominant in one direction, horns move faster than main body, move at 30m/yr, eddying maintains steep slopes on leeward

Question 25

transverse dunes

Answer 25

form similar to barchans but are right angle to wind have steep and less steep sides, often in ergs and can be huge

Question 26

linear or seif dunes

Answer 26

straight or slightly curved, can be 100km long, long steep slip faces on alternate sides, parallel to prevailing wind direction

Question 27

star dunes

Answer 27

slip faces on three or more arms, form where wind is multidirectional, tend to build upwards and can be tallest dunes in the world

Question 28

alluvial fans and bajadas

Answer 28

where rivers leave steep sided valleys and enter adjacent lowlands, reduction in gradient causes sudden energy loss and so deposition happens. Many alluvial fans in a row makes a bajada