The Geosphere

Question 1

How much of Earth is made of ice?

Answer 1

• Ice covers 15 million km^2 at the present day
• 96% -Antarctica and Greenland
• 10% of Earth’s land surface

Question 2

What percentage of fresh water does ice sheet and glaciers and freshwater lakes make up for the earths total amount of fresh water?

Answer 2

• Ice sheets and glaciers = 77.14%
• Freshwater lakes = 0.33%
• (other fresh water is usually found in ground water)

Question 3

What are “Sydharbs”

Answer 3

• Unit of measure of the volume of water that is equivalent to the Sydney harbour.
• One Sydharb = 0.5km^3

Question 4

When do Ice sheets (continental Glaciers) form?

Answer 4

• Occur where snow and ice accumulate over very wide areas.
• Ice may start to accumulate in the mountains and spread to surrounding plains.
• Eventually the ice builds in volume and height and provides its own topography.
• The entire landscape including the mountains are then overwhelmed with ice

Question 5

What are some examples of ice sheets?

Answer 5

• Greenland ice sheet is 1.8 M km3, occupies 7/8 of Greenland and has a maximum thickness of 3 km.
• Antarctic ice sheet is 14 M km3, ice occupies nearly 100% of Antarctica and has a maximum thickness of 4.2 km (equivalent in weight to 1.6 km of rock)
• Large parts of both landmasses are now depressed below present sea level by the weight of ice- (isostacy or glacio isostatic adjustment).

Question 6

What is Isostatic adjustment?

Answer 6

• Isostatic adjustment refers to the transient or long term, nonelastic response of the earth’s lithosphere to loading and unloading due to erosion, deposition, water loading, desiccation, ice accumulation, and deglaciation

Question 7

How does Isostatic Adjustment work?

Answer 7

• Even the strongest materials (including the Earth’s crust) move, or deform, when enough pressure is applied. So when ice by the megaton settled on parts of the Earth for several thousand years, the ice bore down on the land beneath it, and the land rose up beyond the ice’s perimeter

Question 8

What is a Glacio-Isostatic Depression from today?

Answer 8

• The ice over Antarctica is heavy enough to deform the crust, such that when the ice melts, the crust will rebound. Scandinavia is still rebounding at about 1m per century (1cm/yr).

Question 9

What is Glacio-eustatic adjustment?

Answer 9

• Rates of present-day postglacial rebound
• The rebound from glaciers
• The redistribution of water to the oceans by glacial melting

Question 10

Study the diagram of an Alpine (valley) Glacier

Answer 10

https://docs.google.com/document/d/11SlS_6djE3BGAezT2-FeVRTdxG1P1jVyj-u3X2L5qDo/edit?usp=sharing

Question 11

What happens as a glacier moves?

Answer 11

• It grinds the rocks underneath it and carries them down to the end of the valley
• As glaciers melt and thus retreat, they leave a lot of that debris behind and so Terminal moraines are formed.

Question 12

What are Terminal Moraines?

Answer 12

• A moraine (mass of rocks and sediment carried down and deposited by a glacier, typically as ridges at its edges or extremity.) deposited at the point of furthest advance of a glacier or ice sheet

Question 13

What are characteristics that a glacier makes as it retreats?

Answer 13

• U - shaped troughs that held the ice of a glacier
• Arête’s
• Cirque’s
• Paternoster Lakes
• Hanging valleys
• Glacial Erratics

Question 14

What is a Truncated Spur?

Answer 14

• A truncated spur is a spur, which is a ridge that descends towards a valley floor or coastline from a higher elevation, that ends in an inverted-V face and was produced by the erosional truncation of the spur by the action of either streams, waves, or glaciers.

Question 15

What is an Arête?

Answer 15

• An arête is a narrow ridge of rock which separates two valleys. It is typically formed when two glaciers erode parallel U-shaped valleys

Question 16

What is a Cirque?

Answer 16

• A cirque is an amphitheatre-like valley formed by glacial erosion.

Question 17

What is a col?

Answer 17

• The lowest point of a ridge or saddle between two peaks, typically providing a pass from one side of a mountain range to another.

Question 18

What is a Paternoster Lake?

Answer 18

• A paternoster lake is one of a series of glacial lakes connected by a single stream or a braided stream system.

Question 19

What is a hanging valley?

Answer 19

• A valley which is cut across by a deeper valley or a cliff.

Question 20

What are Glacial Erratics?

Answer 20

• A glacial erratic is a piece of rock that differs from the size and type of rock native to the area in which it rests.

Question 21

Study the diagrams of the preglacial valley, the glaciel valley and the postglacial valley

Answer 21

• google doc

Question 22

What are Glacial outwash rivers?

Answer 22

• It is a river containing deposits of sand and gravel carried by running water from the melting ice of a glacier and laid down in stratified deposits
• Colour of the river is usually a milky sort of blue

Question 23

What are Aeolian processes

Answer 23

• Pertain to wind activity in the study of geology and weather and specifically to the wind’s ability to shape the surface of the Earth.

Question 24

What is Loess?

Answer 24

• A loosely compacted yellowish-grey deposit of wind-blown sediment of which extensive deposits occur

Question 25

What are some examples of Aeolian landforms?

Answer 25

• The most striking aeolian land forms are dunes. These are mostly composed of sand grains and concentrate in sand seas or ergs

Question 26

How are sand grains transported?

Answer 26

• Sand grains are transported by wind, via a number of mechanisms: suspension, saltation, and surface creep

Question 27

What is the Aeolian processes of suspension?

Answer 27

• The finer sand particles are moved by the wind, high in the air. They are not affected by gravity and therefore can travel thousands of kilometres before they land on earth again. When they land, it is often because they have combined with raindrops and fall with the rain.

Question 28

What is the Aeolian processes of saltation?

Answer 28

• The most common form of sand transport
• When the wind hits the ground, it causes turbulence, disturbing the sand particles. If the wind has enough velocity, it will cause the particles to start moving (initially just along the ground).
• The required velocity is called critical velocity and varies depending on grain size, vegetation present and the moisture levels of the sand (which holds the sand down, requiring the critical velocity to be greater). As the sand moves, it hits other grains which cause them to bounce up in the air. The wind then picks these airborne particles up and carries them. Gravity causes them to fall back down. If sand lands on a hard surface (e.g., rock), the sand particle will bounce off again, being carried further. If it lands on a sandy surface, it will cause other particles to be disturbed, bounce up and they too will be carried, thus starting off a chain reaction.

Question 29

What is the Aeolian processes of surface creep?

Answer 29

• The larger particles are too heavy to be picked up and carried by the wind so instead, they move along the ground. When they become dislodged by the falling ones, they roll along the ground. Through this process, they are not only moved but by moving against other particles, they erode into smaller particles which can be moved by saltation or suspension.

Question 30

What are the first four types of dunes

Answer 30

• Longitudinal (two gusts of wind coming together from opposite directions makes ridges out of the sand)
• Dome (wind has eroded sounding landscape, leaving behind large dome shaped lumps of sand)
• Barchan (wind blows the sand in one direction and semi-crescent dunes form, facing the direction where the wind is blowing)
• Parabolic (the wind blows the sand in to semi-crescent dunes, however these semi-crescents have the curve facing the wind)

Question 31

What are the second four types of dunes?

Answer 31

• Star (three opposing winds come together to form dunes that look like mountains instead of moving in a pattern like a ridge or a semi-crescent)
• Reversing (to opposing winds come together to form dunes that take the shape of wiggly lines)
• Transverse (the wind blows the sand from one direction and creates waves)
• Barchanoid ridge (similar to Transverse but the tops of the waves are squiggly)

Question 32

Study the diagrams of the dune types and Aeolian processes

Answer 32

• google doc

Question 33

What do desert sands need to form?

Answer 33

• Present-day desert sands are mostly derived from alluvium rather than directly from bedrock weathering in situ. This implies that they need rivers!

Question 34

What is alluvium?

Answer 34

• A deposit of clay, silt, and sand left by flowing floodwater in a river valley or delta, typically producing fertile soil.

Question 35

How did Loess first form?

Answer 35

• Loess deposits formed of silt sized grains are found in those mid latitude areas that were marginal to the Pleistocene ice-sheets.
• Loess is what was left behind by the glaciers as fine grained material and then got blown away and deposited

Question 36

Why is Loess important?

Answer 36

• It is extremely fertile
• It is also known as dust and it plays a key role in the global Fe cycle
• This is because the Loess particles usually ave a coating of Iron oxide and it often blows from the deserts/land into the oceans which is really important

Question 37

How does the dust get to the oceans? Give an example

Answer 37

• Aeolian dusts are blown out of all the arid continents
• The internally-draining rivers of the Lake Eyre Basin and Murray-Darling Basin feed sediment inland to arid regions where it is picked up in dust storms and blown offshore
• Aeolian saltation processes have produced dune fields covering large areas

Question 38

How do rivers impact landscapes?

Answer 38

• Rivers shape the landscape in all environments including relatively dry ones

Question 39

What do rivers do?

Answer 39

• They transport sand and cut through bedrock in land forms