ACTION OF GLACIER
The action of glacier is an important agent of erosion, transportation and deposition in temperate regions or mountainous regions.
TERMS ASSOCIATED WITH GLACIER
Ice: This is solid form of water which results from freezing when the temperature is below 00C.
Snow: This refers to frozen water vapour that falls in form of crystals from the atmosphere.
Snow-Line: It is the lower limit of snow cover on a mountain.
Glacier: This means moving ice i.e large accumulation of ice in motion.
Glaciation: It is the wearing away of the earth surface by glacier.
Snow Field: This is the region or area that is permanently covered by snow
What is glacier? 2. Which parts of the world are mostly affected by glacier?
ACTION OF GLACIER EROSION
Sapping: This is the braking up of rock by alternate freezing and thawing of water at the bottom of cracks.
Plucking: It is the tearing away of rocks which have become frozen on the side or bottom of a glacier.
Abrasion: This is the wearing away of rocks beneath a glacier by the scouring action of the rocks embedded in the glacier.
FEATURES OF GLACIER DEPOSITION IN LOWLAND AREAS
Boulder Clay: This consist of stones of various sizes in a mass of sand and clay.
Erratics: These are transported rock fragments which are composed of materials entirely different from the bedrock of the region where they are deposited. They are deposited when the ice carrying them melt into water.
Drumlins: It is composed mainly of boulder clay.
Eskers: These are long narrow ridges of sand and gravel deposited by melting water. They are usually porous.
Terminal Moraines: They are made up of boulders which are deposited at the edge of the ice-sheet.
Outwash Plain: This is a large area consisting of sand and gravel that are washed down the mountainous zone and deposited to form outwash plain which lies beyond the terminal moraines.
GENERAL EVALUATION QUESTIONS:
1. State the processes of glacier erosion.
2. Describe plucking.
3. What is Time Zone?
- Explain at least three features of glacier deposition in lowland areas.
The action of glacier is more dominant in (a) humid region (b) tropical region (c) temperate region (d) desert region
All are processes of glacier erosion except (a) Plucking (b) Hydration (c) Sapping (d) Abrasion
The breaking down of rocks through the collision of the different rock fragments is called (a) Attrition (b) Abrasion (c) Traction (d) Sapping
All are features of glacier erosion in highland areas except (a) Arete (b) Striations (c) Corries (d) Bay
Which of the following is a feature of glacier deposition? (a) Beach (b) Seifs (c) Boulder clay (d) Delta
State two features of glacier erosion in lowlands.
ACTION OF WAVE
The action of wave as an important agent of erosion, transportation and deposition of material is confined to the coast of seas and oceans. The rate of marine erosion depends on the nature of the rocks, the amount of rock exposed to the sea, the effects of tides and currents and human interference in coast protection.
TERMS ASSOCIATED WITH WAVE
(i) Wave: Wave means turbulent movement of water as a result of wind moving over the water.
(ii) Tide: Tide is the alternate rise and fall of the surface of the sea approximately two times a day.
(iii) Current: Ocean current is the movement of water in the ocean in a particular direction.
(iv) Coast: This refers to the meeting point between the land and the sea.
(v) Shore: This is the part of the land that lies between high water and low water.
(vi) Beach: This refers to the material deposited on the shore by the action of wave.
(vii) Swash: This refers to water thrown up the beach by breaking waves.
(viii) Back wash: This is the water that sucks back and retreats after wash.
(ix) Undertow: This is water which flows near the bottom away from the shore.
PROCESSES OF WAVE EROSION
(1) Corrosion: This is the wearing down of the base of the cliff by wave action.
(2) Attrition: This is breaking down of materials like pebbles, boulders, etc. against cliff faces and against each other, as the wave continues its activities.
(3) Hydraulic action: In this process, fast moving waves force itself into cracks within the base of the cliff under pressure and enlarge the cracks.
(4) Solvent action: This involves the disintegration of rock materials such as limestone in the coast by chemical action of the sea.
Differentiate between swash and backwash.
Describe how a beach is formed.
FEATURES PRODUCED BY WAVE EROSION
(1) Capes and Bays: They are features of marine erosion in coastline which can be made of hard rock (cape) or soft rock (bays). A bay usually contains water and could be used as harbour.
(2) Cliff: These are steep rock faces adjoining the coast. They are formed due to the action of waves on the base of headland which cut backward as the wave action intensifies.
(3) Coastal Cave: A cave is a feature of marine erosion. It is an arch-shaped feature found in steep coast or cliff coast.It may contain blow-holes or geo.
(4) Arch: When two caves approach each other from either side of a headland, they meet to form an arch.
(5) Stack: Continuous action of waves makes an arch to collapse. The seaward portion of the highland that remains is called a stack.
(6) Stump: When the stack is seriously eroded to a point that a small portion is just visible above the sea level, a stump is said to be formed.
(7) Geo: Geo develops when a wave cuts into a cliff, resulting into a narrow hole called a geo. It is formed when a cave collapses.
(8) Gloup or Blowhole: Owing to hydraulic action of wave, a hole might develop at the roof of a cave. Continued erosion will result in the hole piercing through to the surface of the cave and water at times may force itself through these holes to form a gloup or blow-holes.
Features of Coastal Deposition
(1) Beaches: Beaches are made up of sand and gravel. They are depositional features on the coast. Beaches are formed when sand and gravel loosened from the land are moved by waves and deposited along the shore. These deposits of sand and gravel on the shore are called beaches.
(2) Spits: These are ridges of sand and gravel formed by long shore drift across the entrance to coastal inlet by lying on one side to the land and the other side into the ocean.
(3) Bar: Bar is a ridge, usually of sand or rock debris formed by deposition across the mouth of a river or across the entrance of a bay.
(4) Marine dunes and dune belt: Dunes are on shore wind with large force which makes a large amount of coastal sand to move to form marine dunes. Marine dunes will later stretch into dune belts.
Mention any three features produced by wave erosion.
What is an arch?
Describe a wave.
Describe a beach.
What is ocean current?
Explain attrition as a process of wave erosion.
What is a bay?
Essential Geography, O.A. Iwena, Pages 65-68.
- The water thrown up the beach by wave is known as (a) Swash (b) Backwash (c) Current (d) Tide
- Which of these is not a mechanism of wave erosion? (a) Solvent action (b) Attrition
(c) Traction (d) Corrasion
- Steep rocks adjoining the coast are_____ (a) Capes (b) Cliffs (c) Bays (d) Stack
- When two caves meet and unite, they form (a) Stack (b) Stump (c) Arch (d) Bays
- Which of these is not a feature of coastal deposition? (a) Beaches (b) Dunes (c) Spits
- State two differences between Ria coast and Fiord Coast.
- List any three features of coastal deposition.