Forces that shape Earth's crust Flashcards
1
Q
What is weathering?
A
It is the wearing away of rocks and soil by the action
2
Q
What can weather the Earth?
A
Water
Hot and cold (expansion and contraction)
Wind
3
Q
What is erosion?
A
Gradual wearing away of structures
4
Q
What is exfoliation?
A
When expansion and contraction of rocks weakens the first layer of rock, causing it to crack and peel off.
5
Q
What is constantly happening to Earth’s surface?
A
It is being continually worn away
6
Q
What forces wear away the Earth’s surface?
A
Wind
Rain
Frost
Waves
7
Q
What carves out valleys?
A
Rivers
Thick layers of ice that move over the land
8
Q
What creates cliffs?
A
Waves
9
Q
What can create mountain peaks?
A
Water and ice that break up rocks in high areas
10
Q
What causes sand dunes?
A
Winds
11
Q
What is soil erosion caused by?
A
Human activity and natural processes
12
Q
What are the most important agents of weathering?
A
Temperature
Water
13
Q
What are the three types of weathering?
A
Physical
Chemical
Biological
14
Q
What is physical weathering?
A
Physical forces such as frost and temperature changes
15
Q
What is chemical weathering?
A
Chemical changes that weaken rocks
16
Q
What is biological weathering?
A
The action of plants and animals
17
Q
How long does weathering take?
A
It is a slow process
18
Q
What can weathering cause?
A
Many changes to a landscape
19
Q
What are two types of physical weathering?
A
Freeze thaw action
Exfoliation
20
Q
When does free thaw happen?
A
When water collects in cracks in rocks
21
Q
What happens to water when it freezes?
A
It expands
22
Q
What does freezing water do to the walls of a crack in a rock?
A
It puts pressure on them
23
Q
Where does freeze thaw action occur?
A
In cold, wet climates
24
Q
What are the four steps of freeze thaw action?
A
Water fills a crack in a rock
Water freezes from the top of the crack downwards
The ice cannot expand upward because the top is already frozen
The ice expands sideways, putting pressure on the rocks
After many cycles of this, the crack will widen and split the rock
25
Where does exfoliation occur?
In climates with severe temperature changes
26
What parts of the rock are affected by exfoliation?
The outer layers of rock
27
What are the steps of exfoliation?
```
Sun heats up rocks
Outer layers expand
Night cools down rocks
The outer layers contract
After many cycles of this, the outer layers begin to peel off
```
28
What are three types of chemical weathering?
Carbonation
Hydrolysis
Oxidation
29
What chemical has dissolved in droplets of rain water?
Carbon dioxide
30
What does this gas do to the rain?
It turns it into a weak carbonic acid
31
What does limestone contain?
Calcium carbonate
32
What happens when carbonic acid comes into contact with limestone?
A chemical reaction occurs
33
Is calcium carbonate soluble?
No
34
Is calcium bicarbonate soluble?
Yes
35
What is the product of carbonisation?
Calcium bicarbonate
36
What are the steps of carbonisation?
Carbon dioxide mixes with rain water
Forms carbonic acid
Rainwater falls on rocks
The calcium carbonate in rocks reacts with the carbonic acid
The reaction forms calcium bicarbonate
Calcium bicarbonate washes away in rain water
37
What kind of climate does carbonisation occur in the most?
Cold climates
38
What kind of water can hold more carbon dioxide?
Cold water
39
Why does carbonisation happen faster in cold climates?
The carbonic acid is stronger in cold water (can hold more carbon dioxide)
40
In what kind of rocks does oxidation occur?
Rocks that contain iron
41
What is oxidation?
When iron in rocks oxidises (rusts)
42
Why does oxidation cause weathering?
Iron oxide is weaker than rock and is easier to break down
43
What substances does hydrolysis involve?
Silicates and water
44
In what rocks are silicates present?
Sandstone
| Granite
45
What do silicate minerals do?
They absorb water and turn into clay
46
What are the steps of hydrolysis?
Water mixes with silicates
Silicates turn into clay
Clay washes away
47
What can weaken soil and expose rocks to weathering agents?
Burrowing animals
48
What are examples of burrowing animals?
Worms
Moles
Porcupines
49
What can plants cause rocks to do?
They can force the rocks to break apart
50
In what two ways can trees affect weathering?
Their roots can grow through rocks
| When they blow over, they can pull up rocks
51
How do lichens weaken rocks?
The roots of lichens penetrate in between the grains in rocks, loosening them and making them fall away
Lichens contain chemicals that break down rocks
52
How many main ways are there that humans affect weathering?
9
53
What are the nine ways humans affect weathering?
New rocks exposed to weathering by roads
Vegetation removed and soil exposed by machines
Human activities add chemicals to the air, soil and water
Dams take up land which could have been used for farming
Cattle change the soil and rocks when they walk and spread their waste
Heat from fires changes the physical and chemical composition of soil
Underground tunnels weaken rocks and soil
Roads and railways bring pollution to the countryside
Human settlements pollute the air and water
54
What linked forces constantly shape the Earth's surface?
Erosion
Weathering
Deposition
55
What is the difference between weathering and erosion?
Erosion involves the movement of minerals and rocks etc. caused by the breaking down of these things. Whereas weathering is simply the breaking down of these substances
56
How do you identify erosion?
There will always be motion
57
What is deposition?
It is the third step
After weathering has broken down rocks, and erosion has moved the broken down rocks, it will be DEPOSITED somewhere else. This is deposition.
58
How do you identify weathering?
Movement will not be involved. I.e. A rock will crack, but will not move
59
How do you identify deposition?
A mineral/rock etc. That has been moved from one place to another
60
Why are rivers a muddy colour?
It carries different kinds of weathered material
61
What is the river's load?
The material carried by a river
62
What is the river's load made up of?
Sand
Stones
Silt
63
Where do most rivers lead?
Into other rivers as tributaries
| These river's then flow into the sea
64
Where do rivers flow faster?
On steep land
65
What causes downward erosion?
In steep, strong rivers, boulders can be washed away
66
What does downward erosion cause?
A river valley with steep sides
67
What is a waterfall?
A waterfall is a sudden drop in the river's gradient
68
What are Rapids?
Places where the water flows faster, but there is no drop in height
69
What are gorges and canyons?
Deep-sided valleys that have been formed by downward river erosion
70
What is the difference between gorges and canyons?
Gorges are often linked to waterfall formation
| Gorges are usually straighter than a canyon
71
How does a canyon form?
When water flows faster and downward erosion occurs
72
What can cause a river to flow faster?
When there is more water in the river
A drop in sea level
The land is uplifted
73
What is backward erosion?
When river water grinds backwards
74
What causes a gorge?
Backward erosion
75
Why does backward erosion occur?
When a river suddenly narrows, some water will fall back and grind the sand underneath
76
How can you identify canyon?
A deep-sided pathway that has formed for the river
It will usually have softer stone
It is a more meandering type of erosion
77
How do you identify gorges?
They are a steep-sided "pool"
| The type of erosion is fiercer
78
How is a meander formed?
By both erosion and deposition
79
Why does a river meander?
It will choose the path of least resistance
80
When a river turns a bend, which side will be eroded?
The outside
81
Why will the outside of a bend erode?
There is faster-flowing water there
82
When a river turns a bend, which side will minerals be deposited on?
The inside of the bend
83
Why will minerals be deposited on the inside of a bend?
The water will go slower, so some minerals will drop
84
How are ox-bow lakes formed?
The erosion caused by a meander causes the neck of the meander to narrow
The meander neck will eventually become the new river path
The new river path makes its deposits at the join of the original meander
The original meander becomes an ox-bow lake
85
What are levees?
They are natural mounds on river banks
86
How are levees formed?
They are formed when a river floods and deposits minerals on the river bank
87
What increases the height of levees?
Frequent floods
88
What are deltas?
Mounds of deposits formed when two large bodies of water meet
The actual delta is the split water
89
How are deltas formed?
When a river meets the sea, the force of the sea forces the river to slow down
As the river slows down, it deposits silt
This mound of silt grows, becoming an obstacle for the river to flow around
This splits the river into many "streams" which flow into the sea separately
90
What is the difference between a meander and a delta?
A meander is when a river goes around an obstacle that is already there
A delta is when a river creates an obstacle with its deposits
91
What do levees and deltas have in common?
They are both mounds caused by river deposits
92
What is the difference between a levee and a delta?
A levee is formed because of floods
| A delta is formed because a river meets the sea
93
What are headlands?
They are pieces of the cliff that stick out into the sea
94
How are headlands formed?
Soft rock is worn away by the waves bashing against it
The hard rock remains, appearing to jut out into the ocean
This is called a headland
95
What are bays?
Curved areas between headlands
96
What is the main cause of headlands and bays?
Rocks of different hardness and resistance
97
What is a cliff?
It is a steep wall of rock that is formed by wave erosion
98
Why do cliffs have a "bubble" at the bottom of cliffs?
The waves are always there, whereas they only reach higher up during floods
99
What do caves, arches and stacks have in common?
They are different stages in wave erosion
100
What are caves?
They are an early stage of arches and stacks
| It is a hollow carved into a cliff face
101
Why do caves form?
Waves pound against the cliff, and softer rock is swept away
102
What are arches?
A hollow which goes straight through a cliff
103
How do arches form?
When waves erode two sides of a cliff into caves, they may erode all the way through
104
What are stacks?
A single pillar of rock that stands separately from the rest of the cliff
105
How are stacks formed?
After the top of an arch collapses, the pillar of the arch remains
106
What is the most common wave deposition feature?
A beach
107
What is a beach?
A mass of loose sand along the cost
108
How are beaches formed?
Waves can erode the original rock into the soft sand
Or rivers may have deposited this eroded material into the sea
The material was then deposited along the coast
109
What are spits?
They are narrow ridges of sand that stick out into the sea or river mouth
110
What is a longshore drift?
When waves push sand up the coast at an angle. The sand will roll down the beach at a different angle
111
What is a salt marsh?
An area of water that has started to allow plants to grow
| It is a marsh made of salt water
112
What causes a salt marsh?
When salt water is trapped behind a spit
113
What are glaciers?
Large masses of ice that move slowly over the land
114
What kind of erosion does a glacier cause?
Abrasion
115
How do glaciers cause deposition?
When they melt, all the materials within the glacier are deposited
116
What are cirques?
Bowl-shaped hollows in glaciated mountain areas
117
What is an arête?
A ridge caused by glacier erosion
118
How are cirques caused?
When snow falls on a glacier, many layers are formed
The snow compacts into ice
This ice pushes down on a mountain
The pressure causes a depression in the mountain side
As the glacier slowly moves, it erodes a hollow from this depression
119
What is a horn?
The pointy top of a mountain, which sometimes remains after an arête is formed
120
What is a U-shaped valley?
A river valley where all of the spurs have been eroded away
121
What causes U-shaped valleys?
When mountain glaciers meet up in river valleys, they are big enough to erode the river valleys from a V-shape to a U-shape
122
What are truncated spurs?
Spurs that have been eroded by glaciers
123
What are some features created by glacier deposition?
Moraines
Eskers
Drumlins
124
What are the two types of moraines?
Terminal
| Lateral
125
What caused the deposition of glaciers?
When the world heated up and the glaciers began to melt
126
What are moraines?
Moraine means water rock
| Moraines are the rocks left at the side and the end of the valley that the glacier used to occupy
127
What are terminal moraines?
The rocks left at the end of the valley
128
What are lateral moraines?
The rocks left on the side of the valley
129
What are eskers?
They are meandering ridges of sand and stones
130
How are eskers formed?
Rivers that ran underneath the glaciers
131
What are drumlins?
They are rounded hills of rock
132
How big do drumlins get?
50-500 meters high
133
What are some features created by deposition?
Sand dunes
Scree slopes
Beaches
River Deltas
134
What are features created by rivers?
```
Waterfalls
Rapids
Gorges
Canyons
Meander
Ox-bow lakes
Levees
Deltas
```
135
When does river erosion occur?
When a river flows over the land
136
What does the river's load do?
It wears away the land
137
What happens to the river's load as it travels along?
The size of the stones reduce, as they get worn away
138
What do faster-flowing rivers do?
They can transport heavier and larger loads
139
How does downward erosion work?
Large boulders get swept away. Since the river bed is steep, (flows downhill) the boulder will grind away at the river bed with a downward motion
140
How is a waterfall formed?
A river flows over varying degrees of rock
The soft rock wears away quicker
The hard rock will remain
This causes a drop in the river
141
What is a plunge pool?
A deeper pool of water at the bottom of a waterfall
142
How is a plunge pool formed?
This is where the softest rock exists
| It will wear away even faster then the rock of the waterfall
143
What kind of erosion is found in the middle and lower courses of a river?
Sideways erosion and sideways motion
144
What happens to the size of a river in the middle and lower courses?
The river is wider
145
What kind of deposition occurs in the middle and lower courses of a river?
More deposition
146
What is a meander neck?
The gap between the two meanders
147
What will eventually happen to an ox-bow lake?
If there is no water supply (rain) it will eventually dry up
148
What happens when lots of deltas are formed?
The river will split into even more channels, forming a D-shaped area
149
What are the features associated with wave action?
```
Headlands
Bays
Cliffs
Caves
Arches
Stacks
Beaches
Spits
Bars
Lagoons
```
150
What is wave action?
The result of waves pounding in the land
151
Do waves carry a load?
Yes
152
When is wave erosion much greater?
During storms and strong winds
153
How is a cliff formed?
In a similar way to waterfalls. Waves erode the base of rocks on the coast, causing the rocks above to collapse
154
What is a wave-cut platform?
As waves erode the cliff face, it will retreat. The hard rock remain at the bottom. This is called a wave-cut platform
155
How does a wave carry deposition?
Material that is eroded from headlands is transported in waves and currents
156
What is the most common deposition feature in the sea?
A beach
157
How are spits formed?
When there is a bend in the coast, the deposition will continue in the direction of the longshoremen drift. This causes a spit of sand to build up
158
What is a bar?
It is when two spits grow across a bay and join two headlands
159
What is a lagoon?
An area of water behind a bar
160
What are features caused by glaciers?
```
Cirques
Arête
U-shaped valley
Moraines
Eskers
Drumlins
```
161
How did glaciers form?
During the ice age, masses of snow froze together in many layers.
162
How is an arête formed?
When two glaciers erode different sides of a mountain
163
How does wind cause erosion?
It picks up sand and soil and transports it, suspended in the air or bouncing along the ground
164
Where is wind erosion and deposition most obvious?
In places where there is little vegetation
165
What kind of erosion is caused by wind?
Abrasion
166
Where is the most intense abrasion?
Near the ground
167
Why is there more abrasion near the ground?
This is where most of the material is transported
168
What features are created by wind?
Mushroom rocks
Yardangs
Troughs
Sand dunes
169
Which river features are created by erosion?
```
Waterfalls
Rapids
Gorges
Canyons
Meander
Ox-bow lakes
```
170
Which river features are created by deposition?
Levees
| Deltas
171
Which coastal features are created by erosion?
```
Headlands
Bays
Cliffs
Caves
Arches
Stacks
```
172
Which coastal features are created by deposition?
Beaches
Spits
Bars
Lagoons
173
Which glacial features are created by erosion?
Cirques
Arête
U-shaped valley
174
Which glacial features are created by deposition?
Moraines
Eskers
Drumlins
175
Which wind features are caused by erosion?
Mushroom rock
Yardangs
Troughs
176
Which wind features are caused by deposition?
Sand dunes
177
What is a mushroom rock?
A rock where the base is larger than the top?
178
How are mushroom rocks formed?
The rock at the base is softer than at the top
Wind erosion is stronger near the ground
Both of these factors cause the base of the rock erode faster than the top
179
What are yardangs?
Horizontal columns of rock
180
How are are yardangs created?
Wind blows along the ground
Blows away the softer rock quicker
The hard rock remains
The wind blows through these columns of hard rock, where the soft rock used to be.
181
How does deposition occur with the wind?
Materials being carried by the wind are dropped when the speed of the wind decreases
182
What is the most common feature of wind deposition in the desert?
A sand dune
183
Do sand dunes have a constant shape?
No. The shape of a sand dune is constantly being changed by the wind
184
What is a slip face?
The side of a sand dune that is not exposed to the wind
185
Where does deposition occur on a sand dune?
On the slip face
186
Where does the sand deposited on a sand dune come from?
The side of the sand dune that is exposed to the wind
187
How does a sand dune move with the wind?
The side that the wind is blowing on will eventually erode completely. The previous slip face will now become the eroded side
The sand dune has therefore moved in the direction of the wind
188
Are all San dunes the Sam shape?
No
189
What are the three main sand dune shapes?
Barchans
Sief dunes
Transverse dunes
190
What does a barchan look like?
The stereotypical sand dune
| A mound with a meandering ridge
191
What does a sief dune look like?
Like corrugated iron
192
What does a transverse dune look like?
Like nails that have been laid alternately with first the tails being up, then the heads being up
193
When is soil erosion an issue?
When more soil is eroded than is replaced
194
How can humans cause unnatural soil erosion?
Human activities disturb the soil which is then carried away by natural processes of erosion
195
What is the main contributor to soil erosion?
Agriculture
196
What other human activities contribute to soil erosion?
Industry
Deforestation
Construction
Mining
197
Why is soil erosion a bad thing?
Topsoil is removed
Formed over thousands of years
The land becomes infertile
198
How does agriculture contribute to soil erosion?
It removes natural vegetation, which weakens the soil-as does ploughing the land- which makes it easier which means it blows/washes away easier
199
How does overgrazing contribute to soil erosion?
Animals eat the vegetation
| The animals stir up the soil with their feet. This exposes the soil to the elements
200
How does construction contribute to soil erosion?
They require large areas of vegetation to be cleared
Soil is exposed
Soil may also be moved, or covered with concrete and other building materials
201
How does mining contribute to soil erosion?
Surface mining exposes the rocks. The soil may be piled up. The chemicals could pollute the soil
202
What are examples of surface mining?
Open-cast coal and iron ore mines
203
What kinds of machinery contribute to soil erosion and concern agriculture?
```
Ploughs
Seed planters
Crop sprayers
Harvesters
Weeding machines
```
204
Why are these machines damaging?
They are pulled by tractors which churn up the soil
205
How does monoculture contribute to soil erosion?
Certain plants take particular nutrients from the soil. If that plant is planted in the same field year after year, that element of the soil will be completely used up and the soil will be weakened.
206
What is the solution to monoculture?
Crop rotation
207
What is crop rotation?
When new plants are planted in different fields every year / season
208
What causes over- grazing?
Overstocking
209
What is overstocking?
When farmers keep too many animals on their land
210
Why does vegetation reduce erosion?
The roots hold the soil in place. In terms of wind erosion, the plants absorb some of the energy
