Maarg Manthan · Topic 3.1

Endogenic Geomorphic Movements and Diastrophism

Geography › Geomorphic Movements and Plate Tectonics · Topic 3.1

Endogenic movements are forces from inside the Earth that build and deform the surface. Slow diastrophic movements include orogenic movements, which make mountains by folding and faulting, and epeirogenic movements, which raise or lower whole continents, while sudden movements such as earthquakes and volcanism act in minutes. The energy comes from the interior heat of the Earth.

5 min read · UPSC Prelims · Geography · Geomorphic Movements and Plate Tectonics

At a Glance

Source of force Internal heat and pressure of the Earth
Slow movements Diastrophism: orogenic and epeirogenic
Sudden movements Earthquakes and volcanism
Compression Produces folds
Tension Produces faults
Exam link UPSC Prelims, Geography: Geomorphic Movements and Plate Tectonics

Where Does It Fit?

This is the first topic of the category on geomorphic movements and plate tectonics. The previous category dealt with the interior of the Earth, which is the source of the energy used here. The next topic covers exogenic movements, denudation and weathering. Previous topic: Magnetosphere, Auroras and Van Allen Radiation Belts. Next topic: Exogenic Movements, Denudation and Weathering.

What Are Endogenic Movements?

In short: endogenic movements are internal forces that raise, fold, break and shift the crust.

The surface of the Earth is shaped by two sets of forces. Endogenic forces originate inside the Earth and mostly build relief, creating mountains, plateaus and basins, while exogenic forces act at the surface and wear relief down. The endogenic forces are driven by heat in the interior, which comes mainly from the decay of radioactive elements and from the residual heat of the formation of the planet. Geomorphic movements are of two kinds. Sudden movements, such as earthquakes and volcanic eruptions, produce rapid changes. Slow movements, called diastrophism, work over thousands to millions of years. The structure of the interior that powers them is described in Crust, Mantle and Core – Internal Structure of the Earth.

What Is Diastrophism?

Diastrophism is the general term for all processes that deform the crust, producing continents, mountains, plateaus, folds and faults. It includes two broad types of movement.

Feature	Orogenic movements	Epeirogenic movements
Meaning	Mountain building	Continent building
Direction	Mainly horizontal	Mainly vertical
Extent	Narrow belts	Broad regions or whole continents
Results	Folding and faulting; fold mountains	Upliftment and subsidence; plateaus, basins, shoreline changes
Force	Compression or tension	Upward or downward warping

An example of epeirogenic upliftment is the rise of Scandinavia after the melting of the ice sheet, and an example of orogenic movement is the formation of the Himalayas.

How Do Folds Form?

Horizontal compressive forces squeeze the crust and bend layers of rock into folds. The upward arch is an anticline, and the downward trough is a syncline. Folding is the main process in the making of fold mountains such as the Himalayas, the Alps and the Rockies. Folds are classified by the shape of their limbs.

Symmetrical fold: both limbs dip at about the same angle.
Asymmetrical fold: the limbs have unequal slopes.
Monocline: one limb is steep and the other is almost horizontal.
Isoclinal fold: the limbs are parallel to each other.
Overturned and recumbent folds: the fold is pushed so far that one limb lies over the other, and in a recumbent fold the axial plane is nearly horizontal.

How Do Faults Form?

When the crust is stretched, compressed or sheared beyond its strength, rocks break along a plane, and the movement along it is called faulting. The plane is the fault plane. The main types of faults depend on the direction of movement.

Fault	Movement	Caused by
Normal fault	Hanging wall moves down relative to the footwall	Tension
Reverse fault	Hanging wall moves up relative to the footwall	Compression
Thrust fault	Reverse fault with a gentle dip, often moving large masses over great distances	Strong compression
Strike-slip fault	Blocks slide horizontally past each other	Shear

Two features of faulting are important. A block that is raised between two parallel faults is a horst, and a block that has sunk between two faults is a graben, which forms a rift valley, as in the Narmada and Tapi valleys of India and the Great Rift Valley of East Africa. The origin of rift valleys is covered in Divergent Boundaries and Rift Valleys.

What Are Earthquakes and Volcanism Doing Here?

The sudden endogenic movements are earthquakes, which release stress built up along faults, and volcanism, in which molten rock from the mantle reaches the surface. They are treated in Earthquakes – Causes, Focus and Richter Scale and in Volcanism – Causes and Lava Types. As an analytical point, the older idea of separate causes for each movement has been replaced by plate tectonics, which explains folding, faulting, earthquakes and volcanoes as results of the same plate motions, as developed in Plate Tectonics and Types of Plate Boundaries.

Why Is This Topic Important?

Foundation Basis of relief formation
Terms Orogenic and epeirogenic often asked
Link Leads to plate tectonics

What Came Next?

The next topic describes exogenic movements, denudation and weathering. Next topic: Exogenic Movements, Denudation and Weathering.

Key People and Terms

Diastrophism Deformation of the crust
Anticline Upward fold
Syncline Downward fold
Fault Break with movement of rocks
Horst Raised block between faults
Graben Sunken block between faults

Exam Corner

Points to Remember

Orogenic means mountain building; epeirogenic means continent building.
Compression makes folds; tension makes faults.
A graben forms a rift valley.
A horst is a raised block.
Earthquakes and volcanoes are sudden endogenic movements.

Do Not Confuse With

Orogenic and epeirogenic Horizontal and narrow versus vertical and broad
Horst and graben Raised versus sunken block
Anticline and syncline Upfold versus downfold

Memory Hook

Orogenic builds mountains, epeirogenic lifts lands; squeeze folds, stretch faults.

Mains Angle

Questions ask for processes that build relief. These points add depth.

Forces Compression and tension
Scale Narrow orogens, broad epeirogeny
Link Explained by plate tectonics

A Question You May Face

An original practice question, not a past paper question.

“Distinguish between orogenic and epeirogenic movements and explain how folds and faults are formed.”

How to Answer

Define Diastrophism.
Compare Orogenic and epeirogenic.
Folds and faults Compression and tension.
Link Plate tectonics.

GS Relevance

Prelims: diastrophism, orogenic and epeirogenic movements, folds and faults. GS Paper 1: geomorphology.

Frequently Asked Questions

What is diastrophism?

Diastrophism is the term for all slow deformation of the Earth's crust by internal forces. It includes orogenic movements, which build mountains through folding and faulting, and epeirogenic movements, which raise or lower large parts of continents.

What is the difference between orogenic and epeirogenic movements?

Orogenic movements are mainly horizontal and act in narrow belts, producing fold mountains by compression. Epeirogenic movements are mainly vertical and affect broad regions, causing the upliftment or subsidence of continents, plateaus and shorelines, often without folding or breaking of rock layers.

What are anticlines and synclines?

An anticline is an upward arch of folded rock layers, and a syncline is a downward trough. Both are formed when horizontal compressive forces bend the rock layers, and they are the basic units of fold mountains such as the Himalayas and the Alps.

What are horst and graben?

A horst is a block of the crust raised between two parallel faults, while a graben is a block that has sunk between two faults. A graben forms a rift valley, such as the valleys of the Narmada and the Tapi rivers.

What causes normal and reverse faults?

A normal fault forms under tension, when the hanging wall moves down relative to the footwall as the crust stretches. A reverse fault forms under compression, when the hanging wall moves up relative to the footwall as the crust shortens.

PYQ Practice — Statement Analysis

1 Orogenic movements are responsible for the formation of mountains.

True

They involve folding and faulting.

2 A graben is a raised block between two faults.

False

A raised block is a horst; a graben has sunk.

3 Epeirogenic movements mainly act vertically over large areas.