Geomorphic Processes

Notes

Geomorphic processes are the forces that shape the Earth's surface. They are of two kinds.

Endogenic (internal) processes

Diastrophism: orogenic (mountain building, folding) and epeirogenic (uplift or subsidence of large areas) movements, faulting, earthquakes.
Volcanism.
They create relief and are driven by the Earth's internal heat.

Exogenic (external) processes

Weathering, mass wasting, erosion and deposition. Driven by the Sun's energy and gravity.
Gradation: the levelling of the surface, by degradation (erosion, lowering) and aggradation (deposition, building up).

Landforms by agent

Running water: V-shaped valleys, gorges, canyons, waterfalls, potholes, meanders, oxbow lakes, floodplains, levees, deltas, alluvial fans, river terraces; a river's profile has youth, mature and old stages.
Groundwater (karst): sinkholes, caves, stalactites (hang from the roof), stalagmites (rise from the floor), pillars (columns), uvalas, poljes. Seen in limestone areas, e.g., the Karst region of Slovenia; Borra Caves (Andhra Pradesh), Kutumsar caves (Chhattisgarh).
Glaciers: U-shaped valleys, cirques, arêtes, horns (Matterhorn), hanging valleys, fjords, moraines (terminal, lateral, medial, ground), eskers, drumlins, erratics, kames, outwash plains.
Wind (arid regions): deflation hollows, mushroom (pedestal) rocks, zeugen, yardangs, inselbergs, ventifacts; dunes (barchans crescent-shaped; seif longitudinal), and loess.
Waves (coastal): cliffs, wave-cut platforms, sea caves, arches, stacks, stumps; depositional features: beaches, spits, bars, lagoons.

Concepts: Base level (the lowest level to which a river can erode); uniformitarianism (James Hutton: "the present is the key to the past"); the cycle of erosion (W.M. Davis: youth, maturity, old age ending in a peneplain) and Walther Penck's model of slope retreat.

Key Points

Endogenic: diastrophism, volcanism (build relief); exogenic: weathering, erosion, deposition (level it).
Stalactite hangs; stalagmite rises; both in limestone caves.
Glacial: U-valleys, cirques, moraines, drumlins; wind: barchans, mushroom rocks; waves: stacks and arches.
Davis: cycle of erosion ending in a peneplain.
Base level controls river erosion.

MCQs

Q1. Stalagmites are formed:

(a) Hanging from a cave roof
(b) Rising from a cave floor
(c) By glaciers
(d) By wind
Ans: (b).

Q2. U-shaped valleys are the work of:

(a) Rivers
(b) Glaciers
(c) Wind
(d) Waves
Ans: (b).

Q3. A barchan is a:

(a) Crescent-shaped sand dune formed by wind
(b) Glacial deposit
(c) Coastal landform
(d) River feature
Ans:
(a).