Maarg Manthan · Topic 3.16

Mass Movements: Heave, Flow, Slide; Slow, Rapid and Landslide Categories

Geography › Geomorphic Processes and Landform Evolution · Topic 3.16

Mass movement is the downslope movement of rock, regolith and soil under the direct pull of gravity, without a flowing agent like a river or glacier. Water usually helps by adding weight and reducing friction. The movements are grouped as heave (creep and soil heave), flow (earthflow, mudflow and debris flow) and slide (rockslide, slump and debris slide), and by speed as slow, rapid and landslide categories. Landslides are a major hazard in the Himalaya, the Western Ghats and the Nilgiris.

6 min read · UPSC Prelims · Geography · Geomorphic Processes and Landform Evolution

At a Glance

Driving force Gravity
Helper Water adds weight and lowers friction
Slow Creep, solifluction
Rapid Mudflow, debris flow, slides, falls
India About 12.6 per cent of land is landslide-prone
Exam link UPSC Prelims, Geography: Geomorphic Processes and Landform Evolution

Where Does It Fit?

This topic follows the one on weathering, whose debris it moves downslope. It is the link between the processes of weathering and the work of rivers, glaciers and wind that carry the material away. Previous topic: Effects of Weathering: Exfoliation Domes and Tors. Next topic: Wind (Aeolian) Erosional Landforms: Pediments, Pediplains, Playas, Deflation Hollows, Mushroom Rocks.

What Is Mass Movement?

Mass movement is the downslope movement of rock, soil and debris under the force of gravity, without a carrying agent such as water or ice, although water usually makes it easier. It is controlled by the slope, the nature of the material and the amount of moisture. Mass movements are grouped by speed.

Speed	Type	Example
Slow	Soil creep, solifluction	Gradual shifting of surface soil on slopes; flow of saturated soil in cold regions
Rapid	Mudflow, earthflow, debris avalanche	Water-saturated debris flowing down valleys
Sudden	Landslide, rockfall, slump	Large masses sliding or falling along steep slopes

A landslide is the rapid sliding of a mass of rock or soil. The Himalayas, the Western Ghats and the northeastern hills of India are especially prone to landslides because of steep slopes, young and weak rocks, heavy monsoon rains, earthquakes and construction on slopes.

How Are Mass Movements Classified?

Class	Type	Description	Speed
Heave	Soil creep	Very slow downslope shifting of soil particles, seen in tilted poles and fences	Millimetres to centimetres a year
Heave	Solifluction	Flow of water-saturated soil over frozen ground in cold regions	Slow
Flow	Earthflow, mudflow, debris flow	Water-soaked material flows like a thick fluid, often down gullies after heavy rain	Rapid
Flow	Debris avalanche	Fast flow of rock and debris on steep slopes	Very rapid
Slide	Slump	Rotational sliding of a block of earth along a curved surface	Moderate
Slide	Rockslide and debris slide	Sliding of rock or debris along a plane such as a joint or bedding	Rapid
Fall	Rockfall	Free fall of rock from a cliff	Extremely rapid

The term landslide covers the sudden, rapid types, such as slides, falls and debris flows. Slow movements, like creep, are not noticed day to day, but they shift large amounts of soil.

What Causes and Triggers Landslides?

Steep slopes: weathered material rests close to its limit of stability.
Heavy or prolonged rain: water adds weight, fills pores and cuts friction. The monsoon is the main season in India.
Earthquakes and vibration: shaking from earthquakes, blasting and heavy traffic.
Weak rock and structure: shale, loose debris, and layers dipping out of the slope.
Removal of vegetation: roots bind soil, so deforestation increases risk.
Human activity: road cutting, mining, construction, and unplanned building in hills undercut slopes.
Undercutting: by rivers or the sea at the foot of a slope.

Which Regions of India Are Most Prone, and What Are Recent Events?

The Geological Survey of India estimates that about 12.6 per cent of the land area of India, excluding snow-covered regions, is prone to landslides, mainly in the Himalaya, the Northeast hills, the Western Ghats and the Nilgiris. The hills of the Eastern Ghats are also affected to a lesser degree. The figure is taken from official studies and updated from time to time.

Himalaya: young, steep, fractured rock with heavy rain, as in Uttarakhand and Himachal Pradesh. The 2013 Kedarnath disaster involved floods and debris flows, and the 2021 Chamoli disaster was a rock and ice avalanche.
Western Ghats: the Malin village landslide in Maharashtra in 2014, and the Wayanad landslides in Keralam (Kerala) on 30 July 2024, which killed over 200 people, followed extreme rainfall on steep slopes.
Joshimath: land subsidence reported from January 2023 in this Uttarakhand hill town, linked to weak ground and construction.

The Geological Survey of India prepares landslide susceptibility maps, and the National Disaster Management Authority issued guidelines on landslide management in 2009. Remedies include slope stabilisation, drainage, retaining walls, afforestation, early warning, zoning, and limits on building in vulnerable areas. As an analytical point, most Indian landslides are triggered by rain but made worse by human interference, so land-use planning is as important as engineering.

How Do Mass Movements Link to Other Processes?

Weathering, described in Weathering: Chemical, Physical/Mechanical and Biological Processes, prepares the debris. Mass movement then carries it to streams, which remove it, as in Exogenic Processes: Denudation, Weathering, Mass Movements, Erosion, Transportation, Deposition. The deposit at the foot of the slope, called colluvium, forms a fan or apron. Landslides can also dam rivers and cause floods when the dam bursts, and landslides may trigger tsunamis in coastal waters, as described in Tsunami: Mechanism, Properties and Effects.

Why Is This Topic Important?

Hazard Frequent in India
Terms Types are asked
Policy Disaster management

What Came Next?

The next topic begins the study of the landforms made by wind, the aeolian erosional landforms. Next topic: Wind (Aeolian) Erosional Landforms: Pediments, Pediplains, Playas, Deflation Hollows, Mushroom Rocks.

Key People and Terms

Creep Very slow downslope soil movement
Solifluction Flow of saturated soil on frozen ground
Slump Rotational slide
Debris flow Fast flow of water-laden debris
Colluvium Deposit at the foot of a slope
Mudflow Flow of saturated fine soil

Exam Corner

Points to Remember

Gravity is the force; water is a helper.
Creep is the slowest movement.
About 12.6 per cent of India is landslide-prone.
Wayanad landslide: 30 July 2024.
NDMA landslide guidelines: 2009.

Do Not Confuse With

Creep and solifluction Soil particles shifting versus saturated soil over frozen ground
Mass movement and erosion Gravity alone versus a moving agent
Mudflow and slide Fluid flow versus movement along a surface

Memory Hook

Heave creeps, flow runs, slide drops; gravity pulls and water props.

Mains Angle

Questions ask for causes of landslides and mitigation. These points add depth.

Causes Natural and human
Regions Himalaya and Western Ghats
Measures Zoning and early warning

A Question You May Face

An original practice question, not a past paper question.

“Discuss the causes of landslides in the Himalaya and the Western Ghats and suggest measures for mitigation.”

How to Answer

Define Mass movement.
Causes Slope, rain, shaking, people.
Regions Himalaya and Ghats.
Measures Zoning, drainage, warning.

GS Relevance

Prelims: types of mass movement, causes of landslides, vulnerable regions. GS Paper 1: geomorphic processes; GS Paper 3: disaster management.

Frequently Asked Questions

What is mass movement?

Mass movement is the downslope movement of rock, soil and debris under the pull of gravity, without a flowing agent such as a river. It includes slow movements like creep and rapid ones like mudflows, slides and falls. Water often helps by adding weight and reducing the friction in the material.

What are the types of mass movement?

Mass movements are grouped as heave, flow and slide. Heave includes soil creep and solifluction, flow includes earthflow, mudflow and debris flow, and slide includes slumps, rockslides and debris slides. Rockfalls, where rock drops freely from a cliff, are another type, and rapid forms are called landslides.

What is soil creep?

Soil creep is the very slow, nearly imperceptible downslope movement of soil and weathered material, usually a few millimetres to centimetres a year. It is caused by repeated wetting and drying, freezing and thawing, and gravity. It is seen in tilted fence posts, bent tree trunks and cracked walls.

What causes landslides in the Himalaya?

Landslides in the Himalaya are caused by steep slopes of young, fractured rock, heavy monsoon rain, frequent earthquakes, and human activities such as road building, tunnelling, mining and deforestation. These factors weaken the slopes, and rain often triggers sudden movement of weathered debris.

How can landslide risk be reduced?

Landslide risk can be reduced by mapping hazard zones and avoiding construction in them, building drains and retaining walls, planting deep-rooted vegetation, controlling road cutting and blasting, and installing early warning systems based on rainfall and slope sensors. Community awareness and enforcement of building rules also help.

PYQ Practice — Statement Analysis

1 Gravity is the main force behind mass movement.

True

Water acts as a helper.

2 Soil creep is a rapid mass movement.

False

It is a very slow movement.

3 Deforestation can increase landslide risk.