Aletschgletscher_mit_Pinus_cembra2.jpg
permafrost periglacial spring russia.jpg
the painted desert arid.jpg
Aletschgletscher_mit_Pinus_cembra2.jpg

Glacial Processes & Landforms


Describe and explain glacial processes of erosion, transport and deposition, and landscape features (landforms) in glaciated areas

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Glacial Processes & Landforms


Describe and explain glacial processes of erosion, transport and deposition, and landscape features (landforms) in glaciated areas

How do physical processes create unique landscapes in extreme environments?

Europe's largest glacier, The Aletsch. Valais, Switzerland. [Source]

 
 

glacial environment (n)

An area covered with snow and ice on a permanent/long-term basis, where glacial processes are operating. Can be on different scales including ice sheet, ice caps, glaciers.

landform (n)

a natural feature of the earth's surface

 
 
 
 

GLACIAL SYSTEMS

Europe's largest glacier, The Aletsch, in winter / Eastern Bernese Alps, Valais, Switzerland. [Source]

 

TASK 1

  1. Read the text above and annotate the pdf with information about glacial systems

 

 
 

NATURAL climate change

Glaciers advance when inputs exceed outputs, when there is more accumulation of snow in the winter than melting of snow in the summer.

But what are the historic reasons for changing climates? What causes warmer and colder years? Human-induced climate change plays an important role in the current warming period, but natural, astronomical factors are also responsible for historic changes in climate.

Read the excerpt from "Africa: A Biography of the Continent" by John Reader and make notes on the three astronomical causes of climate change.

 

 

GLACIAL processes of EROSION AND DEPOSITION

 Plucking and Abrasion

Plucking and Abrasion

TASK 2

Define, describe and illustrate the following processes on your A3 worksheet:

  • Freeze-Thaw Weathering

  • Plucking

  • Abrasion

Write a sentence explaining how these three prcesses work together to shape mountain environments.

 
 

landforms of erosion

 
 

landforms of deposition

 

task 3

Screen Shot 2018-10-01 at 14.02.44.png
  1. Read pp 116-120

  2. Draw illustrated diagrams that both define and explain the formation of:

    • cirques/corries & tarns

    • ribbon lakes

    • pyramidal peaks

    • arêtes

    • glacial troughs / u-shaped valleys

    • lateral/medial/terminal moraine

    • erratics

 
 

PLENARY

Explore the area around the Aletsch glacier using the Google Earth link.

Find examples of the landforms above. Screenshot them. Add them into a document and add titles to indicate the landform.

permafrost periglacial spring russia.jpg

Periglacial Processes & Landforms


Describe and explain periglacial processes of freeze-thaw, solifluction and frost heave, and periglacial landscape features, including permafrost, thermokarst, patterned ground and pingos

Periglacial Processes & Landforms


Describe and explain periglacial processes of freeze-thaw, solifluction and frost heave, and periglacial landscape features, including permafrost, thermokarst, patterned ground and pingos

These naturally occurring formations have only been explained by scientists in the last 20 years!

From what you know about periglacial environments (including extreme diurnal temperature ranges with repeated freezing and thawing of ground sediments) could you attempt to explain how these are made?

 Patterned ground with shotgun for scale

Patterned ground with shotgun for scale

 
 

FREEZE-THAW, SOLIFLUCTION & FROST HEAVE

These are the geomorphological processes occurring in periglacial regions which are responsible for the creation of periglacial landscape features. You should refer to these when explaining the formation of periglacial landforms.

 

FREEZE-THAW

 
 

SOLIFLUCTION

Solifluction lobes in the Swiss National Park, Graübunden.

Solifluction literally means flowing soil. It is the slow, downslope movement of water-saturated sediment due to repeated freezing and thawing of the ground, affected by gravity.  

  1. In winter, the soil and water in the soil freezes.

  2. In spring, the upper layer of the soil melts (active layer), releasing water.

  3. The water infiltrates the upper layer of soil but cannot penetrate deeper because of the frozen permafrost underneath.

  4. The water flows slowly downhill under the surface of the soil creating solifluction terraces and solifluction lobes

 
 

FROST-HEAVE

An upwards swelling of soil during freezing conditions caused by an increasing presence of ice as it grows towards the surface, upwards from the depth in the soil where freezing temperatures have penetrated into the soil.

frost heave road.jpg

PERMAFROST

Permafrost is ground that remains continuously at or below 0 degrees Celsius for at least two consecutive years.

Global distribution of permafrost

 
 
 

THERMOKARST

Thermokarst at Jackson Hole Valley, Teton National Park, Wyoming, USA

Thermokarst is a land surface characterised by very irregular surfaces of marshy hollows and small hummocks formed as ice-rich permafrost thaws. Thermokarst occurs in Arctic areas, and on a smaller scale in mountainous areas such as the Himalayas and the Swiss Alps.

Explanation

  1. Water in the soil freezes creating an ice lens, forcing the land upwards in dome shapes (frost heave)

  2. These thaw in spring and collapse, leaving thermokarst lakes

  3. Larger ice lenses remain frozen during spring and summer

 

PATTERNED GROUND

Patterned ground is the distinct, and often symmetrical geometric shapes formed by ground material in periglacial regions. 

Explanation

Partially melted and collapsed lithalsas (heaved mounds found in permafrost) have left circle-like structures on the Svalbard Archipelago (Wikipedia)

  1. Diurnal temperature ranges above and below zero degrees > repeated freezing and thawing of groundwater and subsoil

  2. Upward expansion forces larger stones toward the surface as smaller soils flow and settle underneath larger stones

  3. Areas with larger stones have much less water than areas of finer grained sediments.

  4. Areas of finer sediments expand and contract laterally as freezing and thawing occur, piling larger stones into stripes

  5. Through time, repeated freeze-thaw cycles smooth out irregularities and odd-shaped piles to form the common polygons, circular, and stripes of patterned ground.

 
 

What happens when permafrost thaws?

 

 
 
 

PINGO

A pingo, also called a hydrolaccolith, is a mound of earth covered ice found in the Arctic and subar-ctic that can reach up to 70 m in height and up to 600 m in diameter. The term originated as the Inuvialuktun word for a small hill. The plural form is "pingos".

Pingo National Landmark, Canada

 
 

Explanation

  1. A tundra lake is found above a pocket of unfrozen ground or “talik”

  2. The lake drains and becomes shallower, becoming a small pond

  3. The unfrozen talik below the lake now starts to freeze due to the absence of water above, squeezing the pocket of talik upwards

  4. Continued freezing of the wet soil creates more expansion

 
 

task

  1. Complete the following grid using information from above and the study guide

the painted desert arid.jpg

Hot, Arid Processes & Landforms


Describe and explain physical and chemical weathering in hot arid environments, and erosion, transportation and deposition by wind and water

Explain the formation of hot, arid landscape features, including dunes, wadis, rock pedestals, mesas and buttes

Hot, Arid Processes & Landforms


Describe and explain physical and chemical weathering in hot arid environments, and erosion, transportation and deposition by wind and water

Explain the formation of hot, arid landscape features, including dunes, wadis, rock pedestals, mesas and buttes

 
 

weathering vs. erosion

 
 

weathering in deserts

saltcrystallization.jpg

Salt Crystallisation

Salt crystallisation is a weathering process in deserts that breaks down rock through the formation of salt crystals.

This can occur in two ways, both of are common in hot desert regions where low precipitation and high temperatures cause salt to form below the surface of the rock.

Type 1

  1. Temperatures fluctuate around 26-28˚C
  2. Sodium sulphate and sodium carbonate minerals in rock expand by around 300%
  3. Expansion of salt crystal formation forces joints in rock to crack

Type 2

  1. Sun heats water causing evaporation
  2. Salt crystals left behind on rock
  3. Temperatures rise and salt expands, applying pressure to joints in rock
 

DISINTEGRATION

Disintegration is a process of weathering found in deserts caused by repeated heating and cooling of rock.

Deserts have diurnal temperature ranges of up to 40˚C (difference between day and night temperatures). During the day, rocks heat up and the minerals in the rock expand. During the night, the rock contracts, causing stresses in the outer layers. This causes peeling or exfoliation to occur. Water is a key part of the process, without water the expansion of salt minerals in rock would not occur.

exfoliation disintegration.jpg
 
 

WIND EROSION in deserts

Wind performs two kinds of erosional work: abrasion and deflation.

Abrasion is a process of erosion where loose particles lying on the ground surface may be lifted into the air or rolled along the ground by wind action. In the process of wind abrasion, wind drives mineral particles against an exposed rock or soil surface, wearing down the surface.

The sandblasting action of wind abrasion is usually limited to the bottom meter or two of exposed rock above a flat plain. That’s because sand grains don’t rise much higher into the air. Wind abrasion produces pits, grooves, and hollows in the rock. You’ll often see that wooden utility poles on windswept plains have a protective metal sheathing or a heap of large stones placed around the base. Without this protection, they would quickly be cut through at the base.

Deflation is the removal of loose particles from the ground by wind. Deflation acts on loose soil or sedi- ment, and so dry river courses, beaches, and areas of recently formed glacial deposits are susceptible. In dry climates, much of the ground surface can be deflated because the soil or rock is largely bare of vegetation.

The finest particles, those of clay and silt sizes, are lifted and raised into the air—sometimes to a height of a thousand meters (about 3300 ft) or more. Sand grains are moved by moderately strong winds and usually travel within a meter or two (about 3 to 6 ft) of the ground. Gravel fragments and rounded pebbles can be rolled or pushed over flat ground by strong winds, but they don’t travel far. They become easily lodged in hollows or between other large particles. If there’s a mixture of particles of different sizes on the ground, deflation removes the finer sized particles and leaves the coarser particles behind. 

Source

 

task

  1. Complete the A3 writing frame: describe, explain and illustrate the processes of weathering and erosion in deserts.
 
 

ARID LANDFORMS

 
 

Mesa - Butte - Plateau - Canyon - Wadi - Pediment - Yardang - Zeugen - Salt Pan - Inselberg

 
 
 
 

flash floods

 

Mystery - How did this happen?

 
 
 
 
 
 

drainage basins in hot arid areas

In order to understand how a flash flood like the one above can happen in hot, arid areas, we must first understand how drainage basins work.

Look at the diagram below. How would the drainage basin system and the processes responsible for transferring water be different in hot arid areas?

Flooding occurs when rainfall intensity exceeds infiltration capacity generating surface runoff/overland flow leading to flooding.

Causes of flooding in deserts:

  1. summer convection rainfall bringing high amounts of precipitation
  2. unvegetated desert surfaces reduce interception and infiltration, increasing overland flow
  3. high concentrations of water in wadis, gullies or channels
  4. presence of desert crusts (duricrusts) and other barriers to infiltration (rocks in desert pavement etc).
 

infiltration and surface runoff

CONVECTIONAL RAINFALL

infiltration runoff.jpeg
 
 

task

  1. Draw a labelled diagram to illustrate how flash floods happen in hot, arid environments.
  2. Use all of the information above to help you.
 
 

RIVERS in deserts

task

  1. Name and describe the three main types of river in desert environments
  2. Explain why rivers can have considerable discharges in arid environments.