EXOGENTIC PROCESS AND RESULTANT LANDFORMS
1. Define exogenetic processes and give examples.
Exogenetic processes are external forces acting on the Earth's surface.
They originate from energy derived from the sun, gravity, and atmospheric
conditions. These processes modify landscapes by breaking rocks, moving
materials, and depositing sediments.
-
Examples:
-
Weathering: Breaks down rocks into smaller particles (e.g., frost action in
cold climates).
-
Erosion: Removes and transports soil/rocks (e.g., river erosion forming valleys).
-
Deposition: Deposits materials in new locations (e.g., formation of sand dunes
by wind).
2. How do exogenetic processes shape landforms?
Landforms
are shaped through the interplay of:
-
Weathering: Weakens rocks, making them susceptible to erosion.
-
Erosion: Agents like water, wind, and glaciers carve features such as valleys
and cliffs.
-
Transportation: Moves materials to different areas, where they contribute to
new formations.
-
Deposition: Creates landforms like sand dunes, floodplains, and deltas by
settling eroded materials.
These processes occur
continuously, leading to changes in the Earth’s surface over time.
3. Distinguish between weathering and erosion.
-
Weathering:
-
Breakdown of rocks at their original place (in situ).
-
Involves no movement of materials.
-
Types: Physical (e.g., frost action), chemical (e.g., oxidation), and
biological (e.g., root penetration).
-
Erosion:
-
Includes the removal and transportation of materials by agents such as water,
wind, and ice.
-
Results in the creation of valleys, canyons, etc.
4. What are the main types of transportation in exogenetic processes?
Agents
like water, wind, and ice transport materials in the following ways:
-
Traction: Large particles roll along the surface, pushed by water or
wind.
-
Saltation: Medium particles bounce along the surface in a leapfrog
motion.
-
Suspension: Fine particles are carried within water or air.
- Solution:
Dissolved minerals are transported by the medium (e.g., water).
5. Explain the role of deposition in forming landforms.
Deposition occurs when transporting agents lose energy and drop the
materials they carry. This process forms:
-
Floodplains: Created when rivers overflow and deposit sediments on nearby flat
land.
- Deltas:
Form at river mouths where sediments are deposited.
- Sand
dunes: Build up due to wind carrying and settling sand in arid
regions.
Without deposition,
transported materials would not settle to form new landforms.
Works of a River
6. Describe the role of rivers in the hydrological cycle.
Rivers
are integral to the hydrological cycle as they:
-
Transfer water from land to oceans, seas, or lakes.
- Help in
transporting minerals and nutrients.
-
Maintain the balance of ecosystems by supporting plant and animal
life.
The cycle begins with
evaporation, continues as precipitation, and ends as water flows back to
oceans, completing the loop.
7. What is a river basin? Provide an example.
A river
basin is the area of land drained by a river and its tributaries. It is bounded
by highlands or ridges called divides.
-
Example: The Ganga River Basin covers parts of northern India, Nepal, and
Bangladesh.
8. Define interfluves and their significance.
Interfluves are the elevated areas or ridges between two adjacent river
valleys.
- They
determine the flow of water into different drainage systems.
-
Significance: They act as natural barriers and influence watershed
management.
9. Explain the mechanisms of river erosion.
Rivers
erode land through:
-
Hydraulic action: Water compresses air in cracks, causing rocks to
break.
-
Abrasion: Rocks carried by the river grind against the bed and banks, wearing
them down.
-
Solution: Water dissolves minerals, especially in limestone areas.
10. What are the four types of transportation
by rivers?
-
Traction: Rolling of boulders and pebbles along the riverbed.
-
Saltation: Sand-sized particles bounce along the bed in a hopping
motion.
-
Suspension: Fine sediments float and move with the water.
-
Solution: Dissolved materials are carried invisibly in the water.
11. How are V-shaped valleys formed?
- These
valleys are created in the upper course of rivers where vertical erosion
dominates.
- The
steep slopes and narrow floors give them a "V" shape.
-
Example: Valley of the Kali Gandaki River in Nepal.
12. Write a short note on interlocking spurs.
-
Interlocking spurs are projections of high land that extend into the river
valley.
- The river winds around these spurs because it
lacks enough energy to erode through them.
- Found
in the upper courses of rivers.
13. Define gorges and canyons with examples.
- Gorge:
A narrow, deep valley with steep sides formed by rapid river erosion (e.g.,
Indus Gorge in Ladakh).
- Canyon:
A wider and deeper valley with layered rocks (e.g., Grand Canyon in Arizona,
USA).
14. Explain the formation of waterfalls and plunge pools.
-
Waterfalls form where a river flows over a layer of hard rock underlain by
softer rock. Erosion of the softer rock creates a vertical drop.
- Plunge
pools form at the base due to the force of water and abrasion by sediments.
15. What is a pothole, and how does it form?
- A
pothole is a cylindrical depression in a riverbed.
- Formed
by swirling water and pebbles that grind the riverbed over time.
16. Describe how meanders develop over time.
-
Meanders are curves or bends in a river's course.
- Develop
when the river erodes its outer banks (river cliffs) and deposits sediments on
the inner banks (slip-off slopes).
- Found
in the middle course of rivers.
17. Explain slip-off slope and river cliff in the context of meanders.
-
Slip-off slope: A gentle slope formed on the inner curve of a meander due to
deposition.
- River
cliff: A steep slope on the outer curve caused by erosion.
18. What leads to the formation of oxbow lakes?
-
Meanders are cut off from the river when the neck of the loop is breached,
leaving a U-shaped water body called an oxbow lake.
19. Define flood plains and natural levees.
- Flood
plains: Flat areas near rivers, formed by sediment deposition during
floods.
- Natural
levees: Raised embankments along riverbanks, formed by repeated deposition
during floods.
20. Differentiate between estuaries and deltas.
-
Estuary: A river mouth submerged by tides, forming a funnel-shaped region
(e.g., Hooghly Estuary).
- Delta:
A depositional landform created at a river’s mouth, usually triangular (e.g.,
Sundarbans Delta).
Impact of Global Warming
21. List the three types of deltas with examples.
- Cuspate
Delta: Triangular, pointed deltas formed by limited wave action distributing
sediments symmetrically around the river mouth.
-
Example: Tiber Delta in Italy.
- Arcuate
Delta: Arc-shaped deltas created where tidal influences are minimal, and
sediment supply is abundant.
-
Example: Nile Delta in Egypt.
-
Bird-Foot Delta: Complex deltas shaped like bird feet, formed where river
currents dominate over other forces.
-
Example: Mississippi Delta in the USA.
22. What conditions are favorable for delta formation?
Deltas
form where:
- Rivers
carry and deposit a large quantity of sediments.
- Tidal
ranges are low, minimizing sediment dispersion.
- The
slope at the river mouth is gentle, allowing sediments to
accumulate.
- The
river velocity reduces significantly as it enters a larger water
body.
These conditions
ensure sediment deposition and the creation of deltaic landforms.
23. Describe the impact of global warming on active delta regions.
Active
deltas are significantly impacted by global warming in the following ways:
- Rising
Sea Levels: Leads to the inundation of low-lying delta regions.
-
Saltwater Intrusion: Saline water encroaches into deltaic ecosystems, affecting
agriculture and biodiversity.
- Increased
Erosion: Due to stronger tidal waves and reduced sediment supply from
upstream.
- Habitat
Loss: Mangroves and wetlands in deltas, such as the Sundarbans, are shrinking
due to increased flooding.
24. How has global warming affected the
Sundarbans of Ganga-Padma-Meghna delta?
-
Increased Salinity: Rising sea levels cause saltwater intrusion, harming
mangroves and agriculture.
-
Frequent Cyclones: More frequent storms disrupt ecosystems and human
settlements.
-
Biodiversity Loss: Endangered species like the Bengal tiger face habitat
reduction.
- Land
Submergence: Erosion and flooding threaten the survival of communities and
ecosystems.
The Sundarbans serve
as an example of how sensitive deltaic regions are to climate change.
25. What is the current situation of
Lohachara, New Moore, and Ghoramara islands?
-
Lohachara Island: Completely submerged due to rising sea levels, forcing
displacement of its residents.
- New
Moore Island: No longer exists, submerged by rising waters of the Bay of
Bengal.
-
Ghoramara Island: Currently undergoing severe erosion, with its area rapidly
shrinking and threatening local inhabitants.
These islands
illustrate the severe impacts of global warming in the Sundarbans.
Works of Glacier
26. Define a glacier and explain its
importance as a freshwater source.
A glacier
is a large, slow-moving mass of ice formed by compacted snow.
-
Glaciers store approximately 69% of Earth's freshwater.
- They
act as reservoirs that release water slowly, feeding rivers and lakes during
dry seasons, making them critical for freshwater availability globally.
27. List the types of glaciers and their
characteristics.
-
Continental Glaciers: Large ice sheets covering vast areas like Greenland and
Antarctica.
-
Mountain Glaciers: Found in high-altitude regions, flowing down valleys (e.g.,
Himalayas).
-
Piedmont Glaciers: Spread over plains when mountain glaciers flow beyond
valleys.
28. What is a snowline? How does it vary geographically?
- The
snowline is the lowest altitude at which snow persists throughout the
year.
- It
varies by region:
-
Near the equator, it is at higher altitudes (~5,000 meters).
-
Closer to the poles, it is much lower due to colder temperatures (~600
meters).
29. Write a short note on icebergs, crevasses,
and bergschrunds.
-
Iceberg: A floating mass of ice that has broken off from glaciers or ice
shelves. These are found in polar regions and can pose hazards to
ships.
-
Crevasse: A deep crack in a glacier's surface caused by the movement and stress
within the ice.
-
Bergschrund: A large crevasse at the upper boundary of a glacier, where the ice
separates from the mountain wall. It poses challenges to mountaineers.
30. Explain the mechanisms of glacial
erosion.
Glaciers
erode the land through two main processes:
-
Plucking: The glacier freezes onto rocks and pulls them away as it
moves.
-
Abrasion: Debris carried by the glacier grinds against the bedrock, polishing
and scraping it.
These processes shape
valleys and other glacial landforms.
31. What are the major landforms created by
glacial erosion?
- Corrie:
Bowl-shaped depression on a mountain side.
- Arete:
Sharp ridge separating two corries.
-
Pyramidal Peak: A pointed mountain peak formed by erosion from multiple
glaciers.
-
U-shaped Valleys: Wide valleys with flat floors created by glacial
movement.
- Hanging
Valleys: Smaller valleys left suspended above the main valley.
32. Define moraines and their types with
examples.
Moraines
are ridges of debris deposited by glaciers as they advance or retreat:
- Lateral
Moraine: Found along the sides of glaciers.
- Medial
Moraine: Formed when two glaciers meet and their debris merges.
-
Terminal Moraine: Found at the glacier's end, marking its furthest advance.
33. Describe glacio-fluvial landforms such as
drumlins and eskers.
-
Drumlin: Streamlined hills of glacial deposits formed under the ice. They indicate
the direction of glacier movement.
- Esker:
Long ridges of sediment formed by streams flowing beneath a glacier.
Works
of Wind
34. Describe the predominance of wind action
in deserts.
Wind
plays a dominant role in shaping deserts:
- It
erodes, transports, and deposits materials due to the lack of
vegetation.
- The
arid conditions enhance the formation of sand dunes and other wind-created
features.
-
Example: The Sahara Desert in Africa.
35. What is deflation, and how does it create
hollows?
-
Deflation refers to the removal of loose particles by wind, leaving behind
larger, more resistant materials.
- Over
time, this process creates depressions called deflation hollows (e.g., Qattara
Depression in Egypt).
36. Define zeugen, yardang, and
inselbergs.
- Zeugen:
Tabular rock formations created by wind abrasion and erosion of softer
layers.
-
Yardang: Narrow ridges formed parallel to wind direction due to differential
erosion.
-
Inselberg: Isolated rock hills found in deserts, left after erosion of
surrounding softer material.
37. Explain the difference between barchans
and seif dunes.
Barchans:
Crescent-shaped dunes with horns pointing downwind, formed in areas with
consistent wind direction.
Seif Dunes:
Longitudinal dunes parallel to wind direction, formed in regions with variable
wind.
38. What are loess deposits, and where are
they found?
- Loess
refers to fine, wind-blown dust deposits, which are highly fertile.
- Found
extensively in China’s Loess Plateau, as well as parts of Europe and the USA.
39. How do wind and running water interact to
form landforms like wadis and playas?
Wadis: Dry riverbeds
formed by intermittent streams in deserts.
Playas: Shallow,
temporary lakes formed in desert depressions when rainwater
collects.
These features
highlight the combined effects of wind and water in shaping arid landscapes.
Desert Expansion
40. Discuss desert expansion and suggest
measures to control it, referring to Sahara and Thar deserts.
- Desert
Expansion: Climate change, deforestation, and overgrazing contribute to
desertification, causing fertile land to turn barren.
Examples:
-
Sahara Desert is encroaching on surrounding regions due to climate
change.
-
Thar Desert in India faces degradation from overgrazing and unsustainable
practices.
Measures:
-
Afforestation to stabilize soil.
-
Sustainable farming practices.
-
Water conservation and irrigation techniques.
How are
deflation hollows formed?
Deflation is a wind
erosion process where loose particles like sand and dust are removed by wind,
leaving behind depressions. Over time, these depressions deepen, forming
deflation hollows. An example is the Qattara Depression in Egypt.
What is
an Iceberg?
An iceberg is a large
mass of ice that breaks off (calves) from glaciers or ice shelves and floats in
the ocean. About 90% of its volume remains submerged underwater. Icebergs are
common in polar regions like Antarctica and the Arctic.
How are
bird's foot deltas formed?
A bird's foot delta
forms when a river deposits sediment faster than tidal forces or waves can
redistribute it. The delta develops long, narrow projections (like a bird's
foot) into the water body.
- Example: Mississippi
River Delta in the USA.
What is
an Icecap?
An icecap is a large,
dome-shaped mass of ice that covers a highland area or plateau. Unlike
glaciers, icecaps flow outward from their central points. Examples include the
Vatnajökull Ice Cap in Iceland.
What is
a Snowline?
The snowline is the
lowest elevation where snow remains throughout the year. Its position depends
on climate, latitude, and altitude:
- Near the poles: The
snowline is closer to sea level.
- In the tropics: It
is at higher altitudes, around 5,000 meters.
What is
a Kame?
A kame is a mound of
sand and gravel deposited by meltwater streams within or under glaciers. When
the glacier retreats, the sediment pile remains, forming a distinct hill or
ridge.
What is
a Catchment Area?
A catchment area (or
drainage basin) is the region from which a river or water body collects surface
runoff, groundwater, and precipitation. For example, the Ganga River Basin
collects water from the Himalayas and surrounding plains.
What is
a Drumlin?
A drumlin is a smooth,
elongated hill formed beneath a glacier. It is made of sediment (till) and
shaped by the movement of ice. Drumlins point in the direction of glacier
movement and often occur in clusters, resembling an "upturned spoon."
What is
a Moraine?
A moraine is a deposit
of glacial debris (such as rocks and sediment) left behind by moving glaciers.
Types include:
- Lateral Moraine:
Along the glacier's sides.
- Terminal Moraine: At
the glacier's furthest advance.
- Medial Moraine:
Formed when two glaciers merge.
How is
a Playa Originated?
A playa is a flat, dry
lake bed in arid regions, formed when temporary rainfall collects in a
depression and evaporates, leaving behind sediments or salt crusts. Playas are
common in deserts like the Mojave Desert.
What is
a Demoiselle?
A demoiselle refers to
a slender rock pillar formed in arid regions by wind erosion. The base erodes
faster due to abrasion, leaving the top supported, often resembling a column.
What is
a Canyon?
A canyon is a deep
valley with steep sides, formed by river erosion over millions of
years.
- Example: The Grand
Canyon in the USA, carved by the Colorado River.
What is
a Fjord?
A fjord is a long,
narrow inlet with steep sides, formed by glacial erosion. When glaciers
retreat, seawater floods the valley.
- Example: Norwegian
Fjords.
What is
a Pediment?
A pediment is a gently
sloping rock surface at the base of mountains, formed by weathering and
erosion. It often transitions into deserts or plains.
What is
a Pyramidal Peak?
A pyramidal peak is a
sharp, pointed mountain summit formed when three or more glacial cirques erode
a mountain from different sides.
- Example: The
Matterhorn in the Alps.
What is
a Basket of Eggs Topography?
This refers to a
landscape with multiple drumlins (glacially formed hills), resembling a
"basket of eggs." The drumlins are scattered and aligned in the
direction of glacier movement.
What is
Topography?
Topography refers to
the physical features of a landscape, including mountains, valleys, plains, rivers,
and lakes. It can also describe the detailed mapping of these features.
What is
Salt Weathering?
Salt weathering occurs
when saline water seeps into rock pores, evaporates, and leaves behind salt
crystals. These crystals expand, breaking the rock apart over time. This
process is common in coastal and arid regions.
What do
you mean by River Capture or River Piracy?
River capture, or
river piracy, occurs when a river changes its course and begins flowing into
another river's basin. This process happens due to headward erosion by one
river, which intercepts the flow of another.
Distinguish between Bed and Valley.
- Bed: The floor or
bottom of a river or water body.
- Valley: A broader
geographical depression, typically carved by rivers or glaciers, containing the
riverbed.
How are
Hanging Valleys Formed?
Hanging valleys are
formed when a smaller glacier (tributary glacier) meets a larger glacier. The
smaller glacier’s valley is left "hanging" above the main glacial
trough after the ice melts.
- Example: Waterfalls
often form in hanging valleys.
What is
Dune? Name Some Landforms Formed by Degradation.
- A dune is a hill of
sand formed by wind deposition. Examples include barchans (crescent-shaped
dunes) and longitudinal dunes.
- Landforms from
Degradation: Canyons, gorges, deflation hollows, and pediments.
What is
an Oxbow Lake?
An oxbow lake is a
U-shaped water body formed when a meander of a river is cut off due to erosion
and deposition. Over time, it becomes an isolated lake.
- Example: Oxbow lakes
are common along the Ganga River.
What is the name of Sandy desert in Sahara?
Ans.
Ergs.
Define a glacier.
Ans. A glacier is a mass of snow and ice that
moves slowly over the land away Ans. from the place of accumulation.
Which kind of glacier generates iceberg ?
Ans.
Continental Glacier.
Name the largest glacier valley of India.
Ans.
Siachen.
What is the highest waterfall of the world ?
Ans.
Angel falls in Venezuela.
What is snout ?
Ans.
The glacier's downstream end is known as snout.
Which term is used for the barren snow covered
peaks of hills on the continental glacier region ?
Ans.
Nunataks
What is kettle ?
Ans.
At the time of depositional work of Glacier outwash plain is formed and within
it some kettle like holes are created/formed, and is known as kettle.
Name the deepest Fjord of the world.
Ans.
Sovney of Norway.
Name the layered sediment deposition under
kettle lake
Ans. Varve.
Who put forward the idea of cycle of erosion'?
Ans.
W.M. Davis.
What are the three stages of cycle of erosion ?
Ans.
Youth, maturity and old age.
What is Pediment ?
Ans. The highly eroded plain formed at the
foot of the mountain due to ero- sive actions of both wind and running water in
deserts is called 'Pediment'.
From where the word 'meander' has been derived
?
Ans. The word 'meander' is derived from the
name of a small winding river 'Meanders' in Turkey.
Which is the largest delta in the world ?
Ans. The Ganga -
Brahmaputra Delta is the largest delta in the world.
What is Wadi ?
Ans. The river valley
created by erosive action of rain water due to sudden torrential showers in
desert areas is called 'Wadi'.
What is Playa ?
Ans. The small salt
lakes present in desert regions are called playa.
What is 'sixth power law' ?
Ans. 'Gilbert'
propounded his famous 'sixth power law', which states that the rate of
discharge of water is directly proportional to the velocity of the river.