Geology Mass Movement Flashcards

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Questions and Answers

What is Mass Wasting / Mass Movements?

The downslope movement of earth materials under the influence of gravity.

How are mass movements classified?

Types of movement, type of earth material, amount of water present, rate of movement.

What is creep in geology?

Slow downhill movement of regolith.

What is solifluction?

Low downhill movement of tundra. Signup and view all the answers

What is slumping?

Sliding of regolith as coherent blocks. Signup and view all the answers

What are the types of mass movement?

Mudflows, debris flows, and lahars. Signup and view all the answers

What is a rockslide?

A slide consisting of rock only. Signup and view all the answers

What defines an avalanche?

Turbulent clouds of debris and air. Signup and view all the answers

What are rockfalls?

Vertical freefall of mass. Signup and view all the answers

What are submarine mass movements?

Mass movements occurring underwater. Signup and view all the answers

Why do mass movements occur?

Due to weathering of rock surface and slope instability. Signup and view all the answers

What are downslope forces?

Forces including gravity, the weight of earth materials, and water. Signup and view all the answers

What are resisting forces?

Shear strength that prevents slipping. Signup and view all the answers

What factors determine slope stability?

Type of material, slope angle, topography, climate, and water. Signup and view all the answers

What is the angle of repose?

The maximum angle at which loose material will sustain without failing. Signup and view all the answers

What does climate refer to in geology?

The weather over years or decades. Signup and view all the answers

How does water affect slope stability?

Water saturates slopes and adds weight. Signup and view all the answers

What are triggers of mass movements?

Destabilizing events that cause slope failure. Signup and view all the answers

How can we protect against mass movement disasters?

Through geologic mapping, re-vegetation, regrading, drainage, and stabilization techniques. Signup and view all the answers

Study Notes

Mass Wasting Overview

Mass wasting, or mass movements, is the downslope movement of earth materials driven by gravity.
Occurs continuously on slopes and includes phenomena like landslides.

Classification of Mass Movements

Classified by type of movement, earth material, water content, and movement rate.

Creep

Slow downhill movement of regolith caused by seasonal expansion and contraction.
Influenced by processes like wetting/drying and freezing/thawing.
Grains move perpendicular to the slope during expansion and vertically down by gravity during contraction.

Solifluction

In tundra regions, melted permafrost flows over deeper frozen soil, creating solifluction lobes.

Slumping

Involves sliding of regolith in coherent blocks along a spoon-shaped failure surface.
Characterized by distinctive features like head scarp and toe.
Common along seacoasts and riverbanks; can develop slowly, allowing observation.

Types of Mass Movements

Includes mudflows, debris flows, and lahars, which are water-rich movements.
Speed influenced by water amount and slope angle; able to carry large objects.

Rock and Debris Slides

Sudden downslope movement classified into rock slides (rock only) and debris slides (primarily regolith).
Movement can exceed speeds of 300 km/h due to air cushioning.

Avalanches

Form turbulent clouds of debris and air, occurring when oversteepened snow detaches.
Move with immense force, posing severe risks to all in their path.

Rockfalls and Debris Falls

Involve vertical freefall of bedrock or regolith, which fragments upon impact.
Talus blocks accumulate at the slope base.

Submarine Mass Movements

Often preserved by burial, include submarine slumps, debris flows, and turbidity currents.
Can be of significant size and impact.

Causes of Mass Movements

Result from weathering of rock surfaces and instability of slopes.

Slope Stability

Determined by the balance between downslope forces (gravity, weight of materials, water) and resisting forces (material strength, cohesion, friction).
Steeper slopes increase risk due to larger forces.

Driving Forces

Gravity is the primary driving force pushing material downhill.

Resisting Forces

Shear strength is crucial for preventing slipping.

Factors Influencing Slope Stability

Type of material, slope angle, topography, climate, water, and time.

Angle of Repose

The maximum angle at which loose material can rest without failing.

Climate Impact

Weather patterns over years influence slope conditions; arid regions expose more bare rock, while wet regions support more soil and vegetation.

Role of Water

Water saturation increases slope weight, lubricates grain contacts, can erode hill bases, and cause liquefaction.

Triggers of Slope Failure

Events like shocks, vibrations, and changes in slope can destabilize areas; both natural and human-induced triggers exist.

Protecting Against Disasters

Geologic mapping can identify risk zones.
Strategies include re-vegetation, regrading slopes, drainage to reduce weight, and engineered structures to enhance stability.

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Description

Test your knowledge on mass wasting and mass movements with these flashcards. Learn how these processes are classified and understand the different types of movements and materials involved. This quiz covers essential concepts in geology related to the downslope movement of earth materials.