Chapter 13 - Weathering, Karst Landscapes & Mass Movement

Location: Utah, USA
Key Learning Concepts: After studying, you should be able to understand and explain various geological processes affecting landforms.

Dynamic Equilibrium: Understand the balance of forces acting on materials on slopes.
Weathering: Define weathering and factors affecting its processes.
Physical & Chemical Weathering Processes: Describe processes like frost wedging, salt-crystal growth, hydration, etc.
Karst Features: Review processes and features tied to karst topography.
Mass Movement Categories: Identify different types of mass movements and provide examples.

Examples of weathering: Historical monuments affected by weathering, human-caused sinkhole formation, hazards of mass movements.
Encouraged engagement: Identify local examples of weathering processes or slope dynamics.

Processes shape landscapes in central Utah, including Henry Mountains and Capitol Reef cliffs.

Location: Oso, Washington, occurred March 22, 2014.
Event Details: 18 million tons of material moved down the slope, causing extensive destruction over 2.6 km², destroying 35 houses and killing 41 people.
Causes:
- Previous warning signs of landslide hazards.
- Heavy rainfall contributing to slope instability.
Characteristics of the Landslide:
- Debris-Avalanche Flow: Involves fast-moving, fluidized mass of rock and mud.
- Movement Mechanisms: Rotational slumping at the headscarp, transitioning to a debris flow at the toe of the slope.
Community Response: Rescue operations involving over 600 people.

Mass Movement: Defined as the movement of earth materials down slopes under gravity's influence.
Factors Influencing Mass Movement:
- Heavy rainfall saturation of slopes.
- River erosion causing oversteepening.
- Volcanic activity melting ice and carrying debris downward.
- Earthquakes creating instability.

Dynamic Equilibrium: Landscapes adapt to changing forces, maintaining stability unless a threshold is crossed, prompting a shift to a new equilibrium.
Frequency and Magnitude: Differential impact due to the rarity of large events versus frequent small events in landscape shaping.

Definition: Disintegration of rock without chemical alteration, increasing mineral surface area.
Main Processes:
- Frost Wedging: Ice expands in fractures and joints, leading to rock breakage.
- Thermal Expansion: Rock layers expand and contract, causing outer layers to peel off.
- Salt Crystals: Crystallization from evaporation creating pressure that breaks rocks apart.
- Exfoliation: Removal of overlying pressure leads to cracking and peeling of rock surfaces.

Definition: Decomposition of minerals through chemical reactions with water.
Main Processes:
- Hydration & Hydrolysis: Water combines with or reacts to minerals, altering structure and forming new materials.
- Oxidation: Reaction with oxygen leads to the formation of oxides, such as rusting iron.
- Carbonation: Carbonic acid aids in dissolving minerals, particularly carbonates.
- Differential Weathering: Various rocks weather differently, impacting landscape appearance.

Definition: Landscapes marked by pitted surfaces and underground solutions due to carbonate dissolution.
Common Features:
- Sinkholes: Circular depressions due to subsidence or collapse.
- Cockpit and Tower Karst: Unique formations in tropical climates due to distinct weathering patterns.
- Caves and Caverns: Formed by extensive dissolution processes.

Falls: Rapid movements of rock with little moisture content.
Slides: Mass moves as a unit along a weakness plane — includes translational and rotational slides.
Flows: Mixtures move as slurries, can be debris flows or mudflows.
Soil Creep: Slow, gradual vis-a-vis motion of soil, often seen in wet or frozen conditions.

Activities like mining and development can accelerate mass movement, leading to significant changes in landscapes.
Awareness of geological hazards is crucial for planning and development, given their historical impact on communities.