Epeirogenic forces are result of:
- (a)Horizontal earth movements
- (b)Vertical earth movements
- (c)Mass movements
- (d)Displacement
Correct — B, Vertical earth movements.
Epeirogenic movements are the slow, broad up-and-down movements of large continental blocks. The word comes from the Greek epeiros, a continent, so epeirogeny literally means continent-building.
Because the force acts along the Earth's radius, whole regions rise (uplift) or sink (subsidence) with little disturbance to the layering of the rocks. The strata may tilt or warp gently, but they are typically not crumpled into tight folds.
The idea to carry away: epeirogenic = vertical = continent-building; orogenic = horizontal = mountain-building. Fix the Greek roots (epeiros, continent; oros, mountain) and the direction follows.
- (a)Horizontal earth movements — Horizontal, or tangential, movements act along the surface of the crust rather than along its radius. When they push blocks together they compress and fold the strata; when they pull blocks apart they stretch and fault them.
That is the definition of orogenic (mountain-building) forces, the process that raised fold mountains such as the Himalayas. This option describes orogeny, the companion term to epeirogeny, rather than epeirogeny itself.
- (c)Mass movements — Mass movement is the downslope transfer of rock, soil and debris under gravity: creep, landslides, slumps, rockfalls, solifluction. It works on the surface after weathering has loosened the material.
It is an exogenic process, driven from outside the crust, and is the right answer for gravity-driven downslope transfer of weathered material. Epeirogenic forces are endogenic, generated inside the Earth.
- (d)Displacement — Displacement is a general word for the shift of rock on either side of a fault or fracture. It describes an effect that earth movements leave behind, measured as throw (vertical) or heave (horizontal) along a fault plane.
It is the right answer for the offset produced along a fault. It names an outcome of crustal movement rather than the vertical or horizontal force that produced it.
Diastrophism is the collective name for the endogenic processes that move, elevate or build up portions of the Earth's crust. Its two main branches are told apart by the direction of movement.
Epeirogenic (continent-building) movements are vertical, or radial: they lift or lower broad areas gently, with simple warping. Orogenic (mountain-building) movements are horizontal, or tangential: compression folds the crust into long, narrow mountain belts, and tension fractures it into faults.
Epeirogeny and orogeny are slow, sustained movements, in contrast with earthquakes, which release strain suddenly.
This sits in the geomorphic-processes chapter of physical geography (NCERT Class XI, Fundamentals of Physical Geography, chapter on Geomorphic Processes), under endogenic forces.
The distinction matters for reading landscapes. Raised beaches and marine terraces standing above present sea level record epeirogenic uplift; drowned river valleys can record subsidence.
Folded ranges such as the Himalayas record orogenic compression, and Uttarakhand's Himalayan relief is the work of orogeny.
- Epeirogeny comes from the Greek epeiros (continent) and means continent-building; orogeny comes from oros (mountain) and means mountain-building.
- Epeirogenic movements act vertically, along the Earth's radius, and are also called radial movements.
- Orogenic movements act horizontally, along the crust, and are also called tangential movements.
- Upward epeirogenic movement is uplift and produces emergence; downward movement is subsidence and produces submergence.
- Epeirogenic movements affect broad areas with gentle warping or tilting; orogenic movements deform long, narrow belts through intense folding and faulting.
- NCERT groups orogenic processes, epeirogenic processes, earthquakes and plate tectonics together under diastrophism.
- The term epeirogeny was introduced by the American geologist G. K. Gilbert in 1890.
- Mass movement is an exogenic process: the downslope movement of weathered material under gravity, without a transporting agent such as running water or ice.
Two branches of diastrophism, told apart by the direction of movement: vertical builds continents, horizontal builds mountains.
- Swapping the Greek roots. Epeiros is continent and oros is mountain; read epeirogenic as 'mountain-building' and the direction flips to horizontal.
- Reasoning from the word 'up'. Mountains rise, so vertical feels like mountain-building, but fold mountains are the product of horizontal compression.
- Treating mass movement as an earth movement. It is gravity acting on loose surface material, an exogenic process, not a force inside the crust.
- Reading 'displacement' as a category of force. It names the offset left along a fault, an effect of movement, not a class of movement.
The idea is asked as a direct definition, as here: which direction of movement produces epeirogeny, or which term names vertical movement.
It also comes through the wider term diastrophism — which processes belong under it and which do not — and as an assertion-reason pair that sets orogenic movement against epeirogenic movement.
No eligible match among this question's citable set.
- practice — not a real PYQ
Which one of the following is an example of an epeirogenic movement?
- (a)Folding of sediments into the Himalayan ranges
- (b)Slow subsidence of a broad continental block
- (c)Downslope creep of soil on a hillside
- (d)Sudden release of strain along a fault during an earthquake
Answerb — subsidence of a broad block is a vertical, continent-scale movement, which is epeirogeny.(a) is orogeny, produced by horizontal compression. (c) is mass movement, an exogenic gravity process. (d) is an earthquake, a sudden movement that NCERT lists separately within diastrophism.
- practice — not a real PYQ
Consider the following statements about epeirogenic movements: 1. They act along the radius of the Earth. 2. They typically crumple strata into tight folds. 3. They can cause the emergence or submergence of coastal land. Which of the statements given above are correct?
- (a)1 and 3 only
- (b)2 and 3 only
- (c)1 and 2 only
- (d)1, 2 and 3
Answera — epeirogenic movements are radial (vertical), so 1 is correct, and their uplift or subsidence emerges or submerges coasts, so 3 is correct.Statement 2 describes orogeny: tight folding is the product of horizontal compression, whereas epeirogeny gives gentle warping. That rules out (b), (c) and (d).
- practice — not a real PYQ
In physical geography, the term that covers the processes which move, elevate or build up portions of the Earth's crust is:
- (a)Denudation
- (b)Diastrophism
- (c)Gradation
- (d)Isostasy
Answerb — diastrophism is the collective term for crust-moving endogenic processes, including orogeny, epeirogeny, earthquakes and plate tectonics.(a) Denudation is the wearing down of the surface by exogenic agents. (c) Gradation is the levelling of relief by degradation and aggradation. (d) Isostasy is the state of balance between crustal blocks, a condition rather than a set of processes.