Week 4 - Sequential Landscapes

Question 1

What are sequential landscapes?

Answer 1

Volcanic and tectonic landforms are constructed by internal Earth processes - initial landscapes

Initial landscapes are altered by external processes to give sequential landscapes
* we interact with initial landforms as do landscape processes

Weathering alters rock structure and is a key process
A key erosional process associated with gravity is mass weighting

Question 2

List Common Landscape Processes

Answer 2

Acting inside the Earth:

• Volcanic
• Tectonic Plates

Acting at Earth’s surface:

• Weathering
• Mass movement
• Erosion: aeolian, glacial, fluvial, marine, ground water (karst)

Question 3

List the drivers of Landscape change

Answer 3

Drivers are matter and solar input systems:

1. Solar energy input - influences climate; evaporation from oceans, precipitation as rain, snow, ice.
2. Radioactive disintegration - causes convection; plate movement and uplift of mountains (amongst other things)
   * Each process involves dissipation of potential energy

Question 4

Erosion

Answer 4

Is the dissipation of energy

Question 5

What is weathering? List the two types.

Answer 5

The changes that occur when a rock is exposed at Earth’s surface.

• Many rocks (especially igneous rocks) contain minerals which are not stable under cool, low pressure, wet, slightly acidic conditions
• PHYSICAL processes will affect rock structure
• rocks will react CHEMICALLY to form new stable minerals - the secondary minerals

Question 6

Describe Physical Weathering

Answer 6

• only breaks up the rock - no change to components/minerals - does not require water
  Agents can be
• removal of pressure (unloading)
• heating - sedimentary rock tends to hold water so it shatters apart
  -freezing/thawing
  -abrasion (water, wind, ice)
• salt crystal growth
• plant roots - they grow in thin layer of soil, as they grow they further weaken weathering rock and root respiration (chemical) aids this

Question 7

Describe Chemical Weathering

Answer 7

Is enabled by water:

• acts as bathing solution
• drives chemical reactions like: hydrolysis, dissolution, oxidation/reduction
• sustains plant life which can increase rate of weathering plant roots
• sustains lichens: chelating agents CO2 from microbial respiration - carbonic acid

Question 8

Products of Chemical Weathering

Answer 8

Primary silicates react to form new minerals and a soluble component
e.g. hydrolysis of ORTHOCLASE (very common rock forming mineral) to ilite

Question 9

Oxidation of Granite

Answer 9

Hornblende
Feldspar
Quartz
Biotite

Question 10

What is the fate of weathering products?

Answer 10

• soil formation - in situ (In situ soil means soil that has been naturally deposited or formed in its present location)
• erosion and deposition with soil formed on the loose sediments, subsequent pressure gives rise to sedimentary rocks
• erosive processed dominated by GRAVITY are collectively known as ‘MASS WASTING’

Question 11

What is Mass Wasting? List the types.

Answer 11

Mass wasting shapes landscapes (slope, gravity water)

Types:
1. Soil Creep - Years - force with gravity exceeding friction
2. Earthflow and slump - hours -
Slump - Complex movement of materials on a slope, includes rational slump.
Earthflow - saturated materials flow downslope
3. Landslide - seconds - very fast flow often caused by earthquakes
4. Rockfall - seconds -

Question 12

Granite Weathering

Answer 12

When granite is exposed it weathers fastest on the corners, then on the edges and slowest on the faces. This gives rounded rocks.

Question 13

Geomorphic : What is Aeolian Landforms?

Answer 13

Aeolian landforms result from the action of wind. They are usually found in arid areas (such as deserts) or coastal areas where aeolian processes are dominant and fluvial (water) action are minimal most of the time.

• Loose sediment is abundant/available
• dunes found
• formed out of granular material such as sand

Question 14

What is Erosional Landforms?

Answer 14

Erosional landforms result from action of flowing water eroding material from their original locations, transporting and then depositing material at another location to create areas of higher and lower elevation, usually characterised by rises (hills) and falls (valleys) in the landscape and the clear presence of streams.

• likely to find moderate steep slopes

Question 15

What are Glacial Landforms?

Answer 15

Result from action of ice in landscape. Ice can erode, gouging out steep slopes, levelling surfaces and causing striations (grooves) on the bedrock.

• also transport and deposit materials (as ice melts) as linear ridges known as moraines
• In Australia most glacial landforms are relict (a relief feature or rock remaining after other parts have disappeared)

Question 16

What are Fan Landforms?

Answer 16

Result from the deopisition of material in a fanshaped plan form - these are usually level to gently sloping but can also be moderately sloping if the material is coarse.
Material being deposited usually supplied from upslope (colluvial) or upstream (fluvial)

Question 17

What is a Made Landform?

Answer 17

Result from the direct action of humans, usually with the aid of heavy machinery.
E.g. dams, mines, dumps, trenches, pits, mounds

Question 18

What is a Karst Landform?

Answer 18

Result from the dissolution of calcium carbonate by water on rocks such as limestone.
These can be characterised by tall residual hills above a flat plain and/or subterranean (underground) features such as caves, underground channels and closed depressions (dolines) caused by collapse of underground caverns or channels formed through dissolution.

Question 19

What is a Plain Landform?

Answer 19

Plains are landforms of extremely low relief and generally repeat the landform patterns over broader spatial scales exceeding that extent of 600m.

Question 20

What is a Volcanic Landform?

Answer 20

Are built-up by volcanism and modified by erosional agents.

• when recent they are typically high and very steep landform patterns without stream channels or with erosional stream channels from centrifugal (outwards) or centripedal (inwards) directionality.