Weathering And Erosion

Front 1

Define: Weathering

Back 1

processes that decompose rocks and convert them to loose gravel, sand, clay, and soil

Front 2

Define: Erosion

Back 2

the removal of weathered rocks by moving water, wind, ice, or gravity

Front 3

2 kinds of weathering:

Back 3

1. Mechanical

2. Chemical

Front 4

Put in order:

transport, erosion, deposition, weathering

Back 4

weathering, erosion, transport, and deposition

Front 5

Define: Mechanical Weathering

Back 5

reduces solid rock to small fragments but does not change the chemical composition of rocks/minerals

Front 6

Define: Chemical Weathering

Back 6

occurs when air and water chemically react with rock to alter its composition and mineral content (think of rusting)

Front 7

5 processes cause mechanical weathering

Back 7

1. pressure-release fracturing

2. frost wedging

3. abrasion

4. organic activity

5. thermal expansion and contraction

Front 8

two additional processes result from combinations of mechanical and chemical weathering

Back 8

1. hydrolysis-expansion

2. salt-cracking

Front 9

Define: Pressure-Release Fracturing

Back 9

fracturing of rock that occurs when pressure decreases and the rock expands as tectonic forces raise it from a depth of several kilometers and erosion removes overlying rock

Front 10

Define: Frost Wedging

Back 10

water freezes in a crack in rock and the expansion wedges the rock apart

Front 11

Define: Abrasion

Back 11

the mechanical wearing and grinding of rock surfaces by friction and impact

Front 12

Define: Organic Activity

Back 12

when roots work their way into a crack, expand, and eventually widen the crack

Front 13

Define: Thermal expansion-contraction

Back 13

fracturing of rocks that occurs when temperature changes rapidly, causing the surface of the rock to heat or cool faster than its interior and to expand or contract faster than the interior

Front 14

the 3 important processes of chemical weathering:

Back 14

1. dissolution

2. hydrolysis

3. oxidation

Front 15

Define: Dissolution

Back 15

when mineral or rock passes into solution

Front 16

Define: Hydrolysis

Back 16

water reacts with a mineral to form a new mineral with the water as part of its crystal structure (a decomposition reaction involving water)

Front 17

Define: Oxidation

Back 17

occurs when a mineral reacts with molecular oxygen

Front 18

Define: Salt-Cracking

Back 18

salts that are dissolved in water in the pores of rock crystalize which widens cracks and pushes grains apart

Front 19

Define: Exfoliation

Back 19

fracturing in which concentric plates or shells split from the main rock mass like the layers of an onion

Front 20

Define: Regolith

Back 20

is a thin layer of loose rock fragments, clay, and sand overlying bedrock

Front 21

Define: Soil

Back 21

a mixture of mineral grains, organic material, water, and gas

Front 22

Define: Loam

Back 22

the most fertile soil, a mixture of clay, sand, silt, and a lot of organic matter

Front 23

Define: Litter

Back 23

bits of leaves, stems, and flowers on the soil surface

Front 24

Define: Humus

Back 24

when litter decomposes so that you can no longer determine the origin of individual pieces

Front 25

a typical well-developed soil consists of several layers called:

Back 25

soil horizons

Front 26

List the different soil horizons in order from top to bottom

Back 26

1. O horizon

2. A horizon

3. topsoil

4. B horizon

5. C horizon

Front 27

Define: O horizon

Back 27

the uppermost layer that consists mostly of litter and humus with a small amount of minerals

Front 28

Define: A horizon

Back 28

the second layer down, and is a mixture of humus, sand, silt, and clay

Front 29

Define: Topsoil

Back 29

mixture of O horizon and A horizon

Front 30

Define: B horizon

Back 30

third layer down, and is a transitional zone between topsoil and weathered parent rock; roots and other organic material grow here but the total amount of organic matter is low

Front 31

Define: C horizon

Back 31

lowest layer and consists of partially weathered rock and grades into unweathered parent rock with little organic matter

Front 32

What is another name for the B horizon

Back 32

Sub-soil

Front 33

Define: Leaching

Back 33

downward movement of water and dissolved ions

Front 34

6 factors that control soil characteristics

Back 34

1. parent rock

2. climate

3. rates of plant growth and decay

4. slope aspect and steepness

5. time

6. transport of soil materials

Front 35

Parent rock dictates

Back 35

texture and composition of soil

Front 36

Climate affects

Back 36

soil formation through rainfall and temperature

Front 37

Define: Capillary Action

Back 37

when water is pulled upward through small pores by electrical attraction to the pore walls

Front 38

Define: Pedocal Soil

Back 38

soil formed in arid and semiarid climates characterized by an accumulation of calcium carbonate

Front 39

Define: Caliche

Back 39

a hard soil layer formed when calcium carbonate precipitates and cements the soil

Front 40

Define: Salinization

Back 40

a process whereby salts accumulate in arid or semiarid soil that is irrigated heavily

Front 41

Define: Pedalfer

Back 41

soil type that forms in humid environments, characterized by abundant aluminum and iron oxides and a concentration of clay in the B horizon

Front 42

average annual temperature affects soil formation in two ways:

Back 42

1. chemical reactions proceed more rapidly in warm temperature

2. plant growth/decay are temperature dependent

Front 43

Define: Aspect

Back 43

the orientation of a slope with respect to the Sun

Front 44

Why is time important to the characteristics of soil?

Back 44

chemical weathering occurs slowly in most environments and time is therefore an important factor in determining the extent of weathering

Front 45

Why is soil transport important to the characteristics of soil?

Back 45

deposited sediment mixes with locally formed soil, changing its composition and texture

Front 46

once soil erodes, the clay, sand, and gravel are carried downhill by 4 processes

Back 46

1. streams

2. glaciers

3. wind

4. gravity

Front 47

Define: Mass Wasting

Back 47

downslope movement of earth material, primarily caused by gravity

Front 48

Define: Landslide

Back 48

general term for mass wasting and for the landforms created by mass wasting

Front 49

5 reasons landslides occur

Back 49

1. steepness of slope

2. type of rock and orientation of rock layers

3. nature of unconsolidated materials

4. water and vegetation

5. earthquakes and volcanoes

Front 50

Define: Angle of Repose

Back 50

the maximum slope or steepness at which loose material remains stable

Front 51

Why does the angle of repose cause a landslide?

Back 51

if the slope becomes steeper than the angle of repose, the material slides

Front 52

A vegetated slope is more _____

Back 52

stable

Front 53

An earthquake may cause a landslide by

Back 53

shaking an unstable slope

Front 54

A volcano may cause a landslide when

Back 54

a volcanic eruption melts snow and ice near the top of the volcano causing the water to soak into the slope to release a landslide

Front 55

3 categories of landslides

Back 55

1. flow

2. slide

3. fall

Front 56

Define: Flow

Back 56

loose, unconsolidated soil/sediment moves as a fluid

Front 57

Define: Slide

Back 57

moving of a coherent block of material along a fracture

Front 58

Define: Fall

Back 58

a rapid, free-falling motion

Front 59

Define: Creep

Back 59

slow, downhill flow of rocks/soil under the influence of gravity

Front 60

Define: Mudflow

Back 60

when heavy rain falls on unvegetated soil and the water saturates the soil to form a slurry of mud and rocks

Front 61

Define: Slump

Back 61

when blocks of material slide downhill over a gently curved fracture in rock or regolith

Front 62

Define: Fracture Plane

Back 62

bedrock slides downslope over a fracture plane

Front 63

What kind of landslide does creep occur in?

Back 63

Flow

Front 64

What kind of landslide does a mudflow occur in?

Back 64

Flow

Front 65

What kind of landslide does slump occur in?

Back 65

Slide

Front 66

What kind of landslide does a rockslide occur in?

Back 66

Slide

Front 67

Put in order from slowest to fastest: Slide, Fall, Flow

Back 67

Flow, Slide, Fall