Geomorphology for General Studies UPSC Civil Services Exam
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Geomorphology Study Guide
1. Volcanism...............................................................................................................................................3
1.1 Causes of Volcanism..................................................................................................................................3
1.2 Lava types..................................................................................................................................................4
Andesitic or Acidic or Composite or Stratovolcanic lava...................................................................................4
Basic or Basaltic or Shield lava..........................................................................................................................5
1.3 Volcanic Landforms...................................................................................................................................5
Extrusive Volcanic Landforms...........................................................................................................................6
Intrusive Volcanic Landforms..........................................................................................................................11
1.4 Volcanism Types......................................................................................................................................13
Exhalative (vapour or fumes)..........................................................................................................................13
Effusive (Lava outpouring)..............................................................................................................................14
Explosive (Violent ejection of solid material)..................................................................................................14
Subaqueous Volcanism...................................................................................................................................15
1
,1.5 Eruptive Volcanism Types.......................................................................................................................16
Hawaiian Eruption...........................................................................................................................................18
Icelandic Eruptions..........................................................................................................................................18
Strombolian Eruption......................................................................................................................................18
Vulcanian Eruption..........................................................................................................................................19
Plinian Eruption...............................................................................................................................................20
Pelean Eruption...............................................................................................................................................23
1.6 Hotspot Volcanism..................................................................................................................................24
Mantle Plumes................................................................................................................................................24
1.7 Geysers and Hot Springs.........................................................................................................................34
1.8 Extinct, Dormant and Active volcanoes..................................................................................................37
1.9 Distribution of Earthquakes and Volcanoes across the World...............................................................37
Pacific Ring of Fire...........................................................................................................................................38
Other regions..................................................................................................................................................39
Mediterranean volcanism...............................................................................................................................39
Volcanos in India.............................................................................................................................................40
1.10Destructive Effects of Volcanoes.............................................................................................................40
1.11Positive Effects of Volcanoes..................................................................................................................41
1.12Rocks.......................................................................................................................................................41
Igneous Rocks or Primary rocks......................................................................................................................42
Sedimentary Rocks or detrital rocks...............................................................................................................44
2
, Metamorphic Rocks........................................................................................................................................46
2. Earthquakes..........................................................................................................................................49
2.2 Causes of Earthquakes............................................................................................................................50
2.3 Earthquakes based on the depth of focus..............................................................................................52
Shallow-focus earthquake...............................................................................................................................53
Deep-focus earthquake...................................................................................................................................53
2.4 Distribution of Earthquakes....................................................................................................................54
2.5 Richter magnitude scale..........................................................................................................................55
2.6 Effects of Earthquakes............................................................................................................................60
3. Tsunami................................................................................................................................................61
3.1 Mechanism of tsunami waves................................................................................................................61
3.2 Properties of Tsunami Waves.................................................................................................................63
3.3 2004 Indian Ocean Tsunami....................................................................................................................66
Plate tectonics.................................................................................................................................................66
Tsunami waves................................................................................................................................................66
Shifts in Geography.........................................................................................................................................67
3.4 Warning Systems.....................................................................................................................................68
4. Soil erosion and Landforms...................................................................................................................69
4.1 Water Erosion.........................................................................................................................................69
Raindrop erosion or splash erosion.................................................................................................................69
Sheet erosion..................................................................................................................................................69
Rill and gully erosion.......................................................................................................................................70
Streambank erosion........................................................................................................................................71
Landslide.........................................................................................................................................................71
Coastal erosion................................................................................................................................................72
Glacial erosion.................................................................................................................................................72
4.2 Wind Erosion...........................................................................................................................................72
4.3 Fluvial Landforms and Cycle of Erosion..................................................................................................72
Fluvial Erosional Landforms............................................................................................................................72
Drainage systems (drainage patterns).............................................................................................................82
Fluvial Depositional Landforms.......................................................................................................................89
4.4 Karst Landforms and Cycle of Erosion....................................................................................................94
Sinkhole/Swallow Hole....................................................................................................................................95
Polje/Blind Valley............................................................................................................................................96
Cavern.............................................................................................................................................................96
Arch/Natural Bridge........................................................................................................................................97
Sinking Creeks/Bogas......................................................................................................................................97
Stalactite and Stalagmite................................................................................................................................98
Dry Valley/Hanging Valley/Bourne..................................................................................................................98
The Karst Cycle of Erosion...............................................................................................................................98
4.5 Marine Landforms and Cycle of Erosion.................................................................................................99
Marine Erosional Landforms...........................................................................................................................99
Marine Depositional Landforms....................................................................................................................102
Coastlines......................................................................................................................................................103
4.6 Glacial Landforms and Cycle of Erosion................................................................................................107
3
, Glacial Erosional Landforms..........................................................................................................................108
Glacial Depositional Landforms.....................................................................................................................109
Glacial Cycle of Erosion.................................................................................................................................111
4.7 Arid Landforms and Cycle of Erosion....................................................................................................111
Erosional Arid Landforms..............................................................................................................................111
Arid Depositional Landforms.........................................................................................................................115
5. Lakes...................................................................................................................................................118
5.1 Classification of Lakes...........................................................................................................................119
5.2 Lakes and Man......................................................................................................................................123
5.3 Important Lakes on Earth......................................................................................................................124
6. Plateau................................................................................................................................................128
6.1 Economic significance of plateaus........................................................................................................129
6.2 Plateau Formation.................................................................................................................................130
Thermal expansion........................................................................................................................................130
Crustal shortening.........................................................................................................................................130
Volcanic flood basalts...................................................................................................................................130
Others...........................................................................................................................................................131
6.3 Plateau Types........................................................................................................................................131
Dissected plateau..........................................................................................................................................131
Volcanic plateau............................................................................................................................................132
Others...........................................................................................................................................................132
6.4 Major plateaus of the World.................................................................................................................132
Others...........................................................................................................................................................135
1.Volcanism
A volcano is a vent or a fissure in the crust from which lava (molten rock), ash, gases, rock
fragments erupt from a magma chamber below the surface.
Volcanism is the phenomenon of eruption of molten rock, pyroclastics and volcanic gases
to the surface through a vent.
1.1 Causes of Volcanism
There is a huge temperature difference between the inner layers and the outer layers of
the earth due to the differential amount of radioactivity.
This temperature difference gives rise to convectional currents in the mantle.
The convection currents in the mantle create convergent and divergent boundaries (weak zones).
At the divergent boundary, molten, semi-molten and sometimes gaseous material appears
on earth at the first available opportunity.
The earthquakes here may expose fault zones through which magma may escape (fissure type
volcano).
4
by Pmfias.com
Websites: https://www.pmfias.com and
https://store.pmfias.com Facebook Page:
https://www.facebook.com/PoorMansFriend2485
YouTube: https://www.youtube.com/c/poormansfriend
Geomorphology Study Guide
1. Volcanism...............................................................................................................................................3
1.1 Causes of Volcanism..................................................................................................................................3
1.2 Lava types..................................................................................................................................................4
Andesitic or Acidic or Composite or Stratovolcanic lava...................................................................................4
Basic or Basaltic or Shield lava..........................................................................................................................5
1.3 Volcanic Landforms...................................................................................................................................5
Extrusive Volcanic Landforms...........................................................................................................................6
Intrusive Volcanic Landforms..........................................................................................................................11
1.4 Volcanism Types......................................................................................................................................13
Exhalative (vapour or fumes)..........................................................................................................................13
Effusive (Lava outpouring)..............................................................................................................................14
Explosive (Violent ejection of solid material)..................................................................................................14
Subaqueous Volcanism...................................................................................................................................15
1
,1.5 Eruptive Volcanism Types.......................................................................................................................16
Hawaiian Eruption...........................................................................................................................................18
Icelandic Eruptions..........................................................................................................................................18
Strombolian Eruption......................................................................................................................................18
Vulcanian Eruption..........................................................................................................................................19
Plinian Eruption...............................................................................................................................................20
Pelean Eruption...............................................................................................................................................23
1.6 Hotspot Volcanism..................................................................................................................................24
Mantle Plumes................................................................................................................................................24
1.7 Geysers and Hot Springs.........................................................................................................................34
1.8 Extinct, Dormant and Active volcanoes..................................................................................................37
1.9 Distribution of Earthquakes and Volcanoes across the World...............................................................37
Pacific Ring of Fire...........................................................................................................................................38
Other regions..................................................................................................................................................39
Mediterranean volcanism...............................................................................................................................39
Volcanos in India.............................................................................................................................................40
1.10Destructive Effects of Volcanoes.............................................................................................................40
1.11Positive Effects of Volcanoes..................................................................................................................41
1.12Rocks.......................................................................................................................................................41
Igneous Rocks or Primary rocks......................................................................................................................42
Sedimentary Rocks or detrital rocks...............................................................................................................44
2
, Metamorphic Rocks........................................................................................................................................46
2. Earthquakes..........................................................................................................................................49
2.2 Causes of Earthquakes............................................................................................................................50
2.3 Earthquakes based on the depth of focus..............................................................................................52
Shallow-focus earthquake...............................................................................................................................53
Deep-focus earthquake...................................................................................................................................53
2.4 Distribution of Earthquakes....................................................................................................................54
2.5 Richter magnitude scale..........................................................................................................................55
2.6 Effects of Earthquakes............................................................................................................................60
3. Tsunami................................................................................................................................................61
3.1 Mechanism of tsunami waves................................................................................................................61
3.2 Properties of Tsunami Waves.................................................................................................................63
3.3 2004 Indian Ocean Tsunami....................................................................................................................66
Plate tectonics.................................................................................................................................................66
Tsunami waves................................................................................................................................................66
Shifts in Geography.........................................................................................................................................67
3.4 Warning Systems.....................................................................................................................................68
4. Soil erosion and Landforms...................................................................................................................69
4.1 Water Erosion.........................................................................................................................................69
Raindrop erosion or splash erosion.................................................................................................................69
Sheet erosion..................................................................................................................................................69
Rill and gully erosion.......................................................................................................................................70
Streambank erosion........................................................................................................................................71
Landslide.........................................................................................................................................................71
Coastal erosion................................................................................................................................................72
Glacial erosion.................................................................................................................................................72
4.2 Wind Erosion...........................................................................................................................................72
4.3 Fluvial Landforms and Cycle of Erosion..................................................................................................72
Fluvial Erosional Landforms............................................................................................................................72
Drainage systems (drainage patterns).............................................................................................................82
Fluvial Depositional Landforms.......................................................................................................................89
4.4 Karst Landforms and Cycle of Erosion....................................................................................................94
Sinkhole/Swallow Hole....................................................................................................................................95
Polje/Blind Valley............................................................................................................................................96
Cavern.............................................................................................................................................................96
Arch/Natural Bridge........................................................................................................................................97
Sinking Creeks/Bogas......................................................................................................................................97
Stalactite and Stalagmite................................................................................................................................98
Dry Valley/Hanging Valley/Bourne..................................................................................................................98
The Karst Cycle of Erosion...............................................................................................................................98
4.5 Marine Landforms and Cycle of Erosion.................................................................................................99
Marine Erosional Landforms...........................................................................................................................99
Marine Depositional Landforms....................................................................................................................102
Coastlines......................................................................................................................................................103
4.6 Glacial Landforms and Cycle of Erosion................................................................................................107
3
, Glacial Erosional Landforms..........................................................................................................................108
Glacial Depositional Landforms.....................................................................................................................109
Glacial Cycle of Erosion.................................................................................................................................111
4.7 Arid Landforms and Cycle of Erosion....................................................................................................111
Erosional Arid Landforms..............................................................................................................................111
Arid Depositional Landforms.........................................................................................................................115
5. Lakes...................................................................................................................................................118
5.1 Classification of Lakes...........................................................................................................................119
5.2 Lakes and Man......................................................................................................................................123
5.3 Important Lakes on Earth......................................................................................................................124
6. Plateau................................................................................................................................................128
6.1 Economic significance of plateaus........................................................................................................129
6.2 Plateau Formation.................................................................................................................................130
Thermal expansion........................................................................................................................................130
Crustal shortening.........................................................................................................................................130
Volcanic flood basalts...................................................................................................................................130
Others...........................................................................................................................................................131
6.3 Plateau Types........................................................................................................................................131
Dissected plateau..........................................................................................................................................131
Volcanic plateau............................................................................................................................................132
Others...........................................................................................................................................................132
6.4 Major plateaus of the World.................................................................................................................132
Others...........................................................................................................................................................135
1.Volcanism
A volcano is a vent or a fissure in the crust from which lava (molten rock), ash, gases, rock
fragments erupt from a magma chamber below the surface.
Volcanism is the phenomenon of eruption of molten rock, pyroclastics and volcanic gases
to the surface through a vent.
1.1 Causes of Volcanism
There is a huge temperature difference between the inner layers and the outer layers of
the earth due to the differential amount of radioactivity.
This temperature difference gives rise to convectional currents in the mantle.
The convection currents in the mantle create convergent and divergent boundaries (weak zones).
At the divergent boundary, molten, semi-molten and sometimes gaseous material appears
on earth at the first available opportunity.
The earthquakes here may expose fault zones through which magma may escape (fissure type
volcano).
4
