Geography Quiz: Landslides and Earth Flows

Study Notes

Earth Movements and Flow Types

Earth Flows: Slow movements of soil; distinct from mudflows.
Mudflows: Fast-moving mixtures of mud and water; can be triggered by earthquakes or volcanic eruptions. Common in sloped, semi-arid regions during intense rain.
Avalanches: Landslides in mountainous areas; typically occur on slopes of at least 35°. Often caused by sun melting surface snow, which later refreezes, creating instability.

Avalanche Statistics

Approximately 10,000 avalanches occur annually in western US mountains.
Avalanches can achieve speeds of up to 300 km/h.

Rockfall Characteristics

Defined as rock volume that free falls and impacts a surface; typically occurs in mountainous regions.
High velocity is common, leading to the formation of talus slopes—cone-shaped piles of debris.

Debris Avalanche

Characterized by very high velocity and medium moisture content.
Example: A 1970 event in Peru involved over 100 million m³ of debris, traveling 10 miles and resulting in 18,000 deaths.

Scarification

Refers to human activities that destabilize slopes, such as construction and mining.

Fluvial Geomorphology

Involves stream-related processes of erosion, transportation, and deposition; studies landforms created by these activities.

Drainage Basin Information

Everyone lives within a drainage basin, classified by characteristics such as drainage density, patterns, and stream orders.

Arid Regions and Characteristics

Arid and semi-arid climates occupy 35% of Earth's surface; wind significantly influences erosion in these areas, making deserts prime environments for sediment transport.
Examples of arid regions include Sonoran, Taklimakan, Atacama, and Kalahari Deserts.

Aeolian Erosion

Deflation: Removal of loose particles, creating desert pavement and blowout depressions.
Abrasion: Grinding of rock surfaces via particles suspended in air.

Aeolian Sediment Transport Methods

Saltation: Jumping of sand particles along the surface.
Creep: Gradual movement of larger particles.
Other methods also involve the movement of sediments.

Karst Landscapes and Mass Movement

Karst Topography: Formed by the dissolution of soluble bedrock like limestone; requires specific conditions including high calcium carbonate content and vegetation.
Approximately 15% of Earth's land area exhibits karst features, including sinkholes and caves.

Mass Movements

Defined as any movement of soil, rock, or debris driven by gravity; can be sudden (slope failure) or gradual (creep).
Triggering factors include precipitation, earthquakes, volcanic activity, and human interventions.

Angle of Repose

The maximum slope at which material remains stable, typically ranging from 25° to 40°, influenced by material size and moisture content.

Triggering Mechanisms for Mass Movements

Various events like heavy rainfall, volcanic eruptions, and human activities can trigger mass movements.

Classes of Mass Movements

Include processes like creep, sliding, flowing, and falling of materials due to gravitational pull reaching a critical shear-failure point.

Creep

A slow mass movement resulting in the gradual downward movement of sediments, often exacerbated by freeze-thaw cycles; trees and structures can lean downhill.

Solifluction

A type of earth flow occurring in periglacial regions with permafrost; involves saturation of the surface layer leading to slow movement (1-10 cm/week).

Landslides and Flows

Sudden and rapid movements of soil or bedrock, often medium moisture content, can be triggered by earthquakes.
Flows occur when the addition of water leads to instability, turning earth materials into thick, liquid-like movements.

Description

Test your knowledge of landslides, earth flows, and mudflows, including their causes and characteristics. Learn about the different types of natural disasters that occur in various regions. Improve your understanding of geography and environmental science.