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Geography > Gr.11 Geomorphology 🌍 > Flashcards

Gr.11 Geomorphology 🌍 Flashcards

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1
Q

What is topography?

A

The shape or relief of the land

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2
Q

What does the structure of rocks determine ?

A

The type of landforms and therefore the landscape of an area

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3
Q

What are horizontal rock layers called?

A

Strata/ stratified rock

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4
Q

What are bedding planes?

A

The planes separating horizontal rock layers.

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5
Q

What is the difference between exogenic forces and endogenic forces?

A

Exogenic forces: originate at the earth’s surface and decrease relief by, e.g. weathering and erosion.
Endogenic forces: originate within the earth’s surface and increase the relief, e.g. uplift

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6
Q

What does it mean if rock is uniformly resistant to erosion?

A

Rocks erode at the same rate.

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7
Q

What are 4 horizontally layered rock formations?

A

Hilly landscapes
Basaltic plateaus
Canyons
Karoo landscape

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8
Q

Which is more resistant: dolerite or basalt?

Why?

A

Dolerite. It cools slowly underground. Basalt cools faster on the earth’s surface

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9
Q

What are the 2 types of hilly landscapes that may form?

A

Series of rounded slopes

Hills with narrow gullies and sharp ridges (called badlands)

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10
Q

What causes rounded slopes? Give an example

A

Humid climates: sheet wash occurs and removes the surface material.
Eg. Valley of 1000 Hills, KwaZulu-Natal

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11
Q

What is sheet wash?

A

Gushing run-off

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12
Q

What causes badlands? Give an example

A

Arid regions: sheet wash washes over slopes with little/ no vegetation. Erosion takes place quickly.
E.g. Death Valley, California

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13
Q

What is a basaltic plateau?

A

A lava plateau with steep cliffs.

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14
Q

Give an example of a basaltic plateau

A

The Drakensberg

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15
Q

What causes a basaltic plateau to form?

A

Upward movement of the earth’s crust

Or fissures forming and magma welling up to surface over a long time

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16
Q

How do basaltic plateaus erode?

A

Vertical joints and cracks in the basalt erode to from deep cliffs

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17
Q

Why does a plateau have a flat top?

A

Lava pours onto the surface of the earth. This forms a hard cap rock which is uniformly resistant to erosion.

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18
Q

What is another name for a canyon?

A

A gorge

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19
Q

How does erosion take place in a canyon landscape?

A

Water finds weak places in layers and erodes vertically. The more resistant the layers, the steeper the slopes.

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20
Q

How do canyon landscapes differ in different climates?

A

Dry regions: steep, rugged, cliff-like slopes

Wet regions: hilly with more vegetation

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21
Q

Give an example of a canyon landscape

A

Fish River Canyon, Blyde River Canyon, Grand Canyon

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22
Q

Decide into resistant and less resistant to erosion:

Sandstone, shale, clay, granite, limestone, quartzite

A

Resistant: sandstone, granite, quartzite

Less resistant: shale, clay, limestone

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23
Q

Out of what do Karoo landscapes develop?

A

Canyon landscapes

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24
Q

Describe the rock in a Karoo landscape

A

Resistant hard layer (sill) such as dolerite on top of layers of sandstone and softer shale. Flat topped hills and wide, flat plains

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25
Q

What is a mesa?

A

A flat-topped table mountain wider than it is high

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26
Q

What is a butte?

A

A flat-topped hill higher than it is wode

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27
Q

What is a pointed butte?

A

A narrow hill with a sharp peak

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28
Q

What is a conical hill?

A

A small, pointed hill

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29
Q

Know how to draw and label a mesa, butte etc. 🌻On diagram sheet

A

🌺

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30
Q

Who “discovered” scarp retreat?

A

King

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31
Q

What are 2 other names for scarp retreat?

A

Parallel retreat/ scarp recession

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32
Q

Where does scarp retreat occur?

A

In semi-arid regions

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33
Q

What is scarp retreat?

A

Initially a river erodes into an uplifted landmass. As back washing occurs, the landform retreats on itself. This occurs with stratified rock where the layers of rock are of a different resistance to the cap rock. The pediment becomes a large, flat pediplane.

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34
Q

Who “discovered” slope decline?

A

Davis

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35
Q

Where does slope decline occur?

A

In humid climates

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36
Q

What is slope decline?

A

Rivers erode into uplifted landmasses to form steep slopes. As water rushes down the slope, it becomes less steep until it’s almost flat (peneplane). The upper convex slope becomes concave.

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37
Q

Who “discovered” slope replacement ?

A

Penck

38
Q

What is slope replacement?

A

Uniform rock with equal weathering over the slope. Scree/talus accumulates at the base of the cliff. Slope becomes gentler

39
Q

How can a hilly landscape be useful to people?

A

Humid: contour farming on slopes
Arid: no agricultural value

40
Q

How can a basaltic plateau be useful to people?

A

Tourism

On Deccan plateau: farming on fertile (basalt) soil

41
Q

How can a canyon landscape be useful to people?

A

Tourism- hiking , photography, canoeing

42
Q

How can a Karoo landscape be useful to people?

A

Sheep farming. Tourism.

43
Q

Know how to label a laccolith, dyke, batholith etc.

A

🌺

44
Q

What is a batholith ?

A

A large, dome-shaped intrusion with no bedding planes that occurs deep within the earth

45
Q

What is a laccolith ?

A

Smaller, mushroom-shaped intrusions connected by a pipe, causing the overlying sedimentary strata to dome upwards.

46
Q

What is a lopolith?

A

Saucer-shaped intrusion causing the sedimentary layers beneath it to bend downwards

47
Q

What are dykes?

A

Vertical sheets of dolerite that have intruded between vertical cracks in sedimentary rock.

48
Q

What are sills?

A

Horizontal layers of dolerite that have intruded between the bedding plane and sedimentary layers.

49
Q

How does a granite dome form?

A

Igneous intrusions (batholiths) are exposed to the earth’s surface when the surface material is removed by erosion before chemical weathering takes place below the surface.

50
Q

How do granite domes erode?

A

Exfoliation occurs. Sheets peel off in layers due to contraction and expansion along pressure joints.

51
Q

When will a batholith become a tor?

A

The surface above the batholith erodes slower than the rate of chemical weathering that breaks down the rock underneath the ground.

52
Q

What will happen if the underground chemical weathering of a batholith is too rapid?

A

Only a pile of loose rocks will remain

53
Q

What are the 4 slope elements?

A

Crest
Freeface/ scarp
Talus/ scree/ debris slope
Pediment

54
Q

Describe a crest?

A

The convex-shaped slope. It has a thin covering of soil. Soil creep takes place here.

55
Q

Describe a freeface/ scarp?

A

This is more than 80 degrees, so it’s almost vertical. Rock is exposed here and it’s too steep for any weathered material to accumulate on. It has joints and cracks that widen as it weathers.

56
Q

Describe a talus/ scree slope?

A

Has a constant angle. Material accumulates at a similar rate as it is eroded away so this slope is never buried.

57
Q

What is a crest?

A

The top of a slope

58
Q

What is a freeface/scarp?

A

A cliff near the top of a slope.

59
Q

What is a pediment?

A

The plain at the base of a slope

60
Q

Know how to draw how a batholith becomes a granite dome/ tor. 🌻on diagram sheet

A

🌺

Label contractual joints and pressure release joints on tor

61
Q

How are homoclinal ridges classified?

A

According to the gradient at which the layer dips

the angle between the dip slope and the horizon

62
Q

At what angle does a homoclinal ridge dip?

A

25-45 degrees

63
Q

At what angle does a Cuesta dip?

A

10-25 degrees

64
Q

At what angle does a hogsback ridge dip?

A

More than 45 degrees

65
Q

Give an example of a hogsback ridge

A

Hogsback, Eastern Cape

66
Q

Know how to draw a homoclinal ridge. 🌻 On diagram sheet

A

🌺

67
Q

How can areas with inclined strata be used by people?

A

Eroded dip slope (hard layers) can be used for forestry
Cuesta plains provide valuable agricultural soil
Underground water can be trapped in cuestas
Oil and gas can be trapped in cuestas

68
Q

What is a syncline versus an anticline

A

A dip. An anticline is a peak. (Not definitions)

69
Q

What is exfoliation?

A

When a granite dome becomes exposed, the extreme cooling and heating causes expansion and contraction of the rock. This causes the peeling of layers on the surface of the rock.

70
Q

What is mass movement?

A

The movement of weathered materials down a slope

71
Q

Put soil creep, landslides, mudflow, rock falls and solifluction in order of speed

A 
Soil creep
Solifluction (water-saturated soil)
Landslides
Mudflow
Rock falls
72
Q

What must one take into account when building on a slope? (4)

A

Slope angle, ecology, geology and rainfall of an area

73
Q

What can be done to control mass movement? (7)

A

Vegetation maintained/ planted
Cuttings on the side of a mountain stabilised using concrete or wire mesh.
Stakes inserted into the slope
Drainage instituted
Development on slopes limited
Risk analysis and risk assessment-hazardous areas mapped
Arrangements for landslide disaster management

74
Q

What are the 6 types of mass movement?

A

Soil creep, solifluction, landslides, rock falls, mud flows, slumps

75
Q

Solifluction

A

A very slow down-slope movement of water-saturated soil.

76
Q

Landslide

A

When a large mass of land breaks loose and plunges down a slope.

77
Q

Rockfall

A

Very rapid movement of material on slopes exceeding 40 degrees

78
Q

Mudflow

A

Stream of mud on steep slopes after heavy rain.

79
Q

Soil creep

A

The slow, down-slope movement of soil.

80
Q

Slumps

A

Slope failure caused by rotational movement

81
Q

Where does soil creep occur?

A

A range of climates

82
Q

Where does solifluction occur?

A

In regions where debris becomes saturated after heavy rain or in tundra regions when ground thaws in spring.

83
Q

When do landslides occur?

A

Slopes exceeding 40 degrees with weathering, frost action or earthquakes.

84
Q

When do mud flows occur?

A

On steep slopes in arid regions after heavy rain

85
Q

Where do slumps occur?

A

In areas where softer materials overlie more resistant rocks

86
Q

What are the effects of mass movement on the environment? (4)

A

Major factor in natural erosion
Landslides Block rivers, forming lakes
Landslides Destruction to vegetation and animal life
Landslides Flooding due to damming up of bodies of water

87
Q

What are the effects of mass movement on people? (5)

A

Soil creep damages railroads, building structures and underground pipes.
Landslides damage structures and property. Real estate values are reduced in landslide-prone areas.
Landslides reduce productivity of agricultural lands.
Landslides interrupt transportation systems, causing a loss of industrial productivity
Road closures force road users to take detours

88
Q

On which slope element do boulders and stones collect?

A

The pediment

89
Q

How does an Atlantic air mass flow?

A

From the Antarctic towards the Equator

90
Q

Describe the Benguela current

A

A very cold and very dry body of air

91
Q

What is the main agent of erosion in a Karoo landscape?

A

Rain/rivers

92
Q

How does water contribute to mudslides?

A

It adds weight and volume

Geography (12 decks)

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