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Grade 9 Geography > Surface forces that shape the Earth > Flashcards

Surface forces that shape the Earth Flashcards

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1
Q

Weathering

A

Rocks on or near Earths surface break down into smaller pieces.

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2
Q

Physical weathering

A

Break down of rock by physical forces (into smaller bits of the same rock).

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3
Q

Chemical weathering

A

Chemicals in the air or water react with chemical substances in rock. This weakens them and they break up (rock dissolves).

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4
Q

Biological weathering

A

Weathering that results from the action of living things.

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5
Q

Igneous rock

A

Rock formed when molten rock (magma) cools and solidifies (on or beneath the surface).

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6
Q

Metamorphic rock

A

Rock that has changed over a long period of time (due to heat and or pressure)

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7
Q

Sedimentary rock

A

Are formed by sediment that is deposited over time and then compressed over a long period of time.

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8
Q

What is the earths crust made of?

A

Solid rock.

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9
Q

What are the 3 rock groups?

A

Igneous, sedimentary and metamorphic.

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10
Q

Why is weathering important?

A

The process forms soil.

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11
Q

What is exfoliation?

A

When rock layers peel off.

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12
Q

Explain exfoliation due to unloading.

A

Overlying rock presses down on rock underground.
Over time the overlying rock is worn away, exposing the rock that was underground.
Without the heavy load on top of it the outgrew layers expand and crack and peel off along the cracks.

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13
Q

Explain exfoliation due to expansion and contraction.

A

Rocks in deserts heat up in the day causing the rock to expand and cool down at night causing the rock to contract.
This continual expansion and contraction causes the rock to crack.
Sometimes the outer layer peels off.

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14
Q

What is frost shattering?

A

The process in which rocks are broken up when water in the cracks in the rocks freeze and expand.

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15
Q

How does chemical weathering effect rocks rich in calcium carbonate?

A

Carbon dioxide in the air dissolves with rain water forming carbon acid which reacts with calcium carbonate in the rock making it soluble in water. This causes much of the calcium carbonate to dissolve out of the rock.

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16
Q

Give 2 examples of rocks rich in calcium carbonate.

A

Dolomite and limestone.

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17
Q

How does chemical weathering effect rocks rich in iron?

A

When oxygen reacts with iron, the iron rusts causing a reddish appearance. This causes the rock to weaken and crumble.

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18
Q

What two categories can biological weathering be?

A

Chemical or physical.

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19
Q

Explain chemical biological weathering.

A

Lichen on rocks give off chemicals, which breaks the rocks so that the lichen can get nutrients from the rock.

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20
Q

Explain physical biological weathering.

A

Tree roots grow into joints in rocks. They force the joint to widen and give off chemicals that weather the rock. Burrowing animals can also cause weathering.

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21
Q

Erosion

A

The wearing away and removal of rocks and soil by sea, rivers, wind, ice and gravity.

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22
Q

Deposition

A

Dropping of weathered material (loses energy) and build up new landforms.

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23
Q

Gradient

A

Steepness of a slope.

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24
Q

Interlocking spurs

A

Wedges of land that stick out into the valley from either side.

25
Q

Floodplain

A

The land that is covered by water in times of flood.

26
Q

Meander

A

Huge bends in rivers.

27
Q

Oxbow lake

A

A lake formed by a cut off meander.

28
Q

Delta

A

An area of land formed by deposition and tributaries at the mouth of the river.

29
Q

Silt

A

Fine deposit of mud or clay. Fine particles of weathered materials.

30
Q

What’s the difference between weathering and erosion?

A

Weathering is the process of rocks being broken down into smaller particles, while erosion refers to the movement of these weathered material.

31
Q

What are the main agents of movement?(5)

A

Rivers
The sea
Moving ice (glaciers)
Wind
Gravity

32
Q

What is the material that is transported by an agent of erosion known as?

A

It’s load.

33
Q

What happens as the agent of erosion slows down or loses its energy?

A

It begins to drop or deposit its load.

34
Q

What do rivers display?

A

Features of both erosion and deposition.

35
Q

What do the sediments carried by a river do?

A

They’re erosive and erode the valley.

36
Q

Which directions can erosion be?

A

Downward ie vertical, or lateral.

37
Q

What will the downward erosion do?

A

It will deepen the valley.

38
Q

What will be lateral erosion do?

A

It will widen the valley.

39
Q

Does the shape of the river valley change?

A

Yes, it changes from its source to its mouth where it enters the sea.

40
Q

Explain how the valley looks in the upper course of the river.

A

Interlocking spurs stick into the valley from either side.

41
Q

Explain how the valley looks in the lower course of the river.

A

The river has a gentle gradient, the valley becomes wider and flatter.

42
Q

Where do waterfalls form?

A

Where the river flows over resistant or hard rock which erodes slowly.

43
Q

What does the harder rock in waterfalls form?

A

An obstacle in the river.

44
Q

What happens as the water flows over the obstacle?

A

It erodes the less resistant or softer rock below forming a plunge pool at the bottom of the waterfall.

45
Q

What is the gradient like in the lower course of the river?

A

The gradient is very gentle.

46
Q

What happens to the lower course of the river when the river floods?

A

It spreads out over the land next to the river.

47
Q

What is the flooding of the lower course of the river called?

A

Floodplain.

48
Q

What is deposited on the flood plain?

A

Silt.

49
Q

Why are floodplains good farming areas?

A

The soil is fertile and the gradient is gentle/flat.

50
Q

What happens when a river flows over a gentle gradient?

A

It begins to meander making bends in its path.

51
Q

What happens on the outside of these bends?

A

The river flows fast and erosion takes place forming an undercut slope.

52
Q

What happens on the inside bend?

A

The river flows slowly and deposition takes place forming a slip off slope.

53
Q

What happens when the river cuts through the narrow neck of a meander?

A

It forms an oxbow lake.

54
Q

What happens when a river enters the sea?

A

It slows down and loses energy causing it to deposit its load.

55
Q

What does this deposition of silt form?

A

A delta which is very fertile.

56
Q

Where is the Nile Delta?

A

In Egypt in Africa.

57
Q

What shape is the Nile delta?

A

An arcuate or fan shape.

58
Q

What shape is the Mississippi delta?

A

A birdsfoot.

Grade 9 Geography (5 decks)

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