Geomorphology, Rivers & Glaciers

Question 1

Name the four different geological time scales.

Answer 1

• eons
• eras
• periods
• epochs

Question 2

Describe how Earth has changed over time.

Answer 2

• Temperature of the climate has risen
• Continents have split apart
• Valleys have been formed by erosion
• Rivers and lakes have been formed by erosion and glaciers

Question 3

Describe the key steps in the rock cycle.

Answer 3

• magma erupts from the volcano
• magma cools and forms solid (igneous) rock
• rock gets weathered and breaks down
• rock gets transported into rivers and seas
• rock gets weathered in the rivers (abrasion and attrition)
• rock breaks down into sediment
• sediment builds up on the seabed and compacts into layers and forms sedimentary rock
• sedimentary rock gets pushed down by pressure and heat and becomes metamorphic rock
• metamorphic rock gets crushed deeper into the ground and forms igneous rock
• magma erupts from the volcano
• etc…

Question 4

What are the main characteristics of metamorphic rocks?

Answer 4

• formed when either igneous or sedimentary rocks change form
• heat and/or pressure will cause the elements in the original rock to react and re-form
• highly resistant to erosion and often used in building materials

Question 5

What is weathering?

Answer 5

Weathering is the process of breaking down rocks. There are four different types of weathering.
- freeze-thaw
- biological
- physical
- chemical

Question 6

What are the key features and processes within a drainage basin?

Answer 6

A drainage basin is the area of land around a river that is drained by the river and its tributaries.

Question 7

How does a river change from its source to its mouth?

Answer 7

• gets wider
• in upper section of river, usually steep and narrow
• in middle section of river, usually sloping and wide
• in lower section of river, usually flat and very wide

Question 8

How do waterfalls form?

Answer 8

A waterfall forms in many steps:
- A river flows over bands of less resistant (softer) and more resistant (harder) rocks.
- The less resistant rock is more quickly worn away due to differential erosion.
- The river erodes the rocks with three different processes: hydraulic action, corrasion and corrosion.
- The river undercuts the harder rock, leaving an overhang, which becomes unsupported and collapses into the plunge pool below.
- After the overhang forms, some of the rocks are swirled around by the river and this helps to form a deep plunge pool below the waterfall. The plunge pool is also deepened during times of high discharge, when hydraulic action is most powerful.
- The waterfall is moved upstream, the process continues and a steep-sided gorge is cut back into the hillside.

Question 9

How do meanders form?

Answer 9

• Starts with a straight river.
• Small bends form due to uneven flow.
• Erosion happens on the outside of bends by hydraulic action and abrasion. The river becomes deep here. A river cliff forms.
• Deposition happens on the inside of bends. Slip off slope.
• Bends become wider and more curved.
• A meander is formed.

Question 10

What are the main causes of flooding (natural and human)?

Answer 10

• deforestation
• snowmelt
• heavy rainfall
• infrastructure Like roads that create impermeable surfaces that increases surface run off meaning more water gets to the river more quickly

Question 11

How can places reduce the risk of flooding using hard engineering?

Answer 11

• flood defences (eg flood walls in Miami)
• dredging
• dams and reservoirs
• embankments

Question 12

How can places reduce the risk of flooding using soft engineering?

Answer 12

• afforestation
• not building on flood plains

Question 13

Why have specific locations experienced severe flooding events?

Answer 13

Keswick 2015:
- Storm Desmond month of rainfall in one day
- Steep slopes cause rapid surface run off
- Deforestation caused by sheep farming
- Infrastructure like roads, causing surface runoff

Question 14

What are the impacts of major flooding events?

Answer 14

In 2015, 50,000 homes were affected by flooding in Cumbria. This caused damages of £500,000,000. Cumbrian councils spent £2.6 billion on flood defences to ensure nothing similar happened again. Roads and bridges were washed away

Question 15

What are glaciers?

Answer 15

A huge, slowly moving mass of ice that forms over many years. They very, very slowly erode paths through mountains, forming valleys.

Question 16

How do glaciers form?

Answer 16

• snow falls in the same place
• gradually compacts, forming ice
• usually form above the snowline (above 3000 metres)

Question 17

Where are glaciers currently located around the world?

Answer 17

• Greenland
• Antarctica
• Himalayas
• Arctic
• Alps
• Andes
• Rockies
• New Zealand
• Mt. Kilimanjaro
• Patagonia
• Iceland

Question 18

Why does the global distribution of glaciers change over time?

Answer 18

Climate Change
- Ice melts faster
- Lack of snowfall

Question 19

How do glaciers shape the landscape? Identify the key processes.

Answer 19

• plucking; rocks become frozen into the bottom and sides of the glacier. As the glacier moves downhill it ‘plucks’ the rocks frozen into the glacier from the ground
• abrasion; as the glacier moves downhill, rocks that have been frozen into the base and sides of the glacier scrape the rock beneath. The rocks scrape the bedrock like sandpaper, leaving scratches called striations behind

Question 20

How does glacial ice create corries?

Answer 20

• snow gathers in mountain hollows (holes or depressions)
• as the ice moves downhill, it sticks to the back walk and plucks rock from the surface, steepening them
• freeze thaw action also loosens rocks on the back wall
• ice moving with loose rock acts like sandpaper and deepens the hollow by abrasion
• ice in a corrie has a rotational movement which means that the front of the corrie is less eroded and a lip forms
• the glacier melts, often leaving a tarn (also known as a corrie loch)

Question 21

How does glacial ice create erratics?

Answer 21

• glacier plucks rock from the valley floor or sides
• glacier carries rock in its basal layer (bottom layer of the ice where material is trapped)
• after hundreds of kilometres, deposition or melting begins
• glacier loses energy and can no longer carry the rock
• glacier deposits rock in a new location

Question 22

What eon are we currently in?

Answer 22

Phanerozoic

Question 23

What era are we currently in?

Answer 23

Cenozoic

Question 24

What are the main characteristics of igneous rocks?

Answer 24

• formed when magma solidifies
• as magma cools, mineral crystals begin to grow
• crystals will grow and form a hard crystalline rock

Question 25

What are the main characteristics of **sedimentary** rock?

Answer 25

- formed due to the build-up of sediments over time - weathered and eroded material is built up in layers - as more material is added, the pressure will push any air and water out and compact the material together into a high rock - often contain fossils of plants and animals

Question 26

The main difference between **intrusive** and **extrusive** igneous rocks is that **intrusive** rocks cool within the volcano and **extrusive** rocks cool on the earth’s surface. What does this cause and why does it make a difference to the strength of the rock?

Answer 26

When magma cools and solidifies, it forms crystals. The slower the magma cools, the more crystals are formed. The crystals grow and interlock to form a hard crystalline rock which gives it a lot of strength. **Extrusive** rocks have fewer crystals than **intrusive** rocks and therefore they have less strength within them.

Question 27

What are the two main types of glaciers?

Answer 27

- *Alpine glacier*; forms in the mountains - *Continental sheet*; spread out over land and sea

Question 28

How does glacial ice form arêtes?

Answer 28

- two corries form back to back - as the glaciers erode, the back walls of a corrie get closer and closer, forming a *ridge* - continued erosion makes the ridge narrower with steeper edges

Question 29

How does glacial ice form pyramidal peaks?

Answer 29

- where three or more corries and arêtes meet - glaciers erode backwards towards each other, carving out the rocks by plucking and abrasion - freeze thaw weathers the top of the mountain, creating a sharply-pointed summit

Question 30

How does glacial ice create glacial troughs?

Answer 30

- where three or more corries and arêtes meet - glaciers erode backwards towards each other, carving out the rocks by plucking and abrasion - freeze thaw weathers the top of the mountain, creating a sharply-pointed summit

Question 31

How does glacial ice form hanging valleys?

Answer 31

The glacial ice forms valleys. A hanging valley is a smaller side valley left hanging above the main U-shaped valley formed by a tributary glacier.

Question 32

How does glacial ice form misfit streams?

Answer 32

Glaciers erode the ground, forming deep valleys. Before the glaciers came, there were rivers. When the glacier eventually melts, the river is much too small for the valley. This is known as a misfit stream.

Question 33

What is moraine?

Answer 33

Material deposited by a glacier at points alongside it.

Question 34

What is lateral moraine?

Answer 34

Material deposited along both sides of the glacier. This moraine is usually made up of weathered material that has fallen from the valley sides above the glacier.

Question 35

What is medial moraine?

Answer 35

Material deposited in the middle of the glacier. This is caused by the lateral moraines of two glaciers when they meet.

Question 36

What is terminal moraine?

Answer 36

Material deposited at the end of the glacier.

Question 37

What is erosion?

Answer 37

Erosion is the wearing away of rock along the coastline. There are four types of erosion: - Hydraulic action - Abrasion - Attrition - Solution

Question 38

What is transportation?

Answer 38

Transportation is the movement of rocks in water. There are four different types: - solution - suspension - saltation - traction

Question 39

What is deposition?

Answer 39

Deposition is when the water loses velocity. This causes it to drop the material it has been carrying. Factors leading to deposition are: - waves starting to slow down and lose energy - shallow water - sheltered areas - little or no wind

Question 40

What is the watershed?

Answer 40

The watershed is the area of high land forming the edge of a river basin.

Question 41

What is the source of a river?

Answer 41

The source of the river is where the river begins.

Question 42

What is the mouth of a river?

Answer 42

The mouth of a river is where a river meets the sea.

Question 43

What is a confluence?

Answer 43

A confluence is the point at which two rivers meet.

Question 44

What is a tributary?

Answer 44

A tributary is a small river or stream that joins a larger river.

Question 45

What is a channel?

Answer 45

The channel is where the river flows.

Question 46

How are rapids formed?

Answer 46

- A river flows over bands of less resistant (softer) and more resistant (harder) rocks. - The less resistant rock is more quickly worn away due to differential erosion. - The river erodes the rocks with three different processes: hydraulic action, corrasion and corrosion. - This repeats over and over and the river becomes more and more turbulent as the water is flowing in many different directions.

Question 47

How are gorges formed?

Answer 47

A river flows over bands of less resistant (softer) and more resistant (harder) rocks. - The less resistant rock is more quickly worn away due to differential erosion. - The river erodes the rocks with three different processes: hydraulic action, corrasion and corrosion. - The river undercuts the harder rock, leaving an overhang, which becomes unsupported and collapses into the plunge pool below. - After the overhang forms, some of the rocks are swirled around by the river and this helps to form a deep plunge pool below the waterfall. The plunge pool is also deepened during times of high discharge, when hydraulic action is most powerful. - The waterfall is moved upstream, the process continues and a steep-sided gorge is cut back into the hillside.

Question 48

How are V-Shaped valleys formed?

Answer 48

- Rivers begin high up in the mountains, so they flow quickly downhill, eroding the landscape vertically. - The river cuts a deep notch down into the landscape using hydraulic action, where the sheer force of the water gets into small cracks and breaks down the sides of the river valley. - As the river erodes downwards, the sides of the valley are exposed to freeze-thaw weathering which loosens the rocks, and steepens the valley sides. - The rocks which have fallen into the river an assist the process of corrasion and this leads to further erosion. - The river transports the rocks downstream and the channel becomes wider and deeper creating a V-shaped valley between interlocking spurs.

Question 49

What is hydraulic action?

Answer 49

Hydraulic action is the sheer power of the waves as they smash against rock. Air becomes trapped in cracks in the rock, and this causes the rock to break apart.

Question 50

What is solution in terms of erosion?

Answer 50

Solution is when sea water dissolves certain types of rocks. In the UK, chalk and limestone cliffs are prone to this type of erosion.

Question 51

How are estuaries formed?

Answer 51

1. A river meets the sea or ocean. 2. The river slows down as it reaches the coast. 3. Freshwater from the river mixes with salty seawater. 4. Sediment carried by the river is dropped (deposited). 5. Layers of mud and sand build up over time. 6. A wide, muddy area called an estuary is formed.

Question 52

How are oxbow lakes formed?

Answer 52

1. Meanders become very curved over time. 2. Erosion happens on the outer bends, making the neck of the meander narrower. 3. During a flood or high flow, the river breaks through the narrow neck. 4. The river creates a new, straighter channel. 5. The old meander loop is cut off from the main river. 6. The cut-off loop becomes an oxbow lake.