Unit 2 Gradational Processes

Chapter 10: Weathering

Differences between Physical and Chemical Weathering

  • Physical (mechanical) weathering: No change in chemical composition.

  • Chemical weathering: Includes changes in chemical composition.

Forms of Weathering

Physical Weathering

  • Frost shatter: Water in joints and cracks freezes, causing rocks to break apart.

  • Growth of plant roots: Roots grow into cracks, similar effect as frost shatter.

  • Thermal expansion: Expansion and contraction of rock due to temperature changes.

  • Exfoliation: Thin layers of rock peel off the rock face.

Chemical Weathering

  • Solution: Rain absorbs CO2 and forms carbonic acid, which dissolves rocks.

  • Hydrolysis: Carbonic acid reacts with silicates, increasing clay content.

  • Oxidation: Oxygen in water changes iron to iron oxide, which can dissolve and be carried away.

Differences Between Weathering, Erosion, and Mass Wasting

  • Erosion: Transportation of weathered materials.

  • Mass wasting: Downhill movement of weathered materials caused by gravity.

  • Weathering: Breakdown of rock into smaller pieces.

Chapter 11: Mass Wasting

What is Mass Wasting

  • Downhill movement of weathered rock and soil, caused by gravity, can be sudden or gradual.

Causes of Mass Wasting

  • Instability from water seeping into soil causing expansion.

  • Weight addition or expansion/contraction due to freeze-thaw cycles.

  • Urbanization (logging) that removes vegetation and alters drainage patterns.

Ways to Stabilize Slopes

  • Bolts anchored deep into rock faces.

  • Concrete layers sprayed on surfaces.

  • Pipes to drain excess water.

  • Terracing to reduce slope angle.

  • Snow sheds.

  • Retaining walls.

Types of Mass Wasting

  • Scree formations: Rocks tumble and accumulate.

  • Soil seep: Gradual soil movement, causing leaning trees.

  • Landslide: Soil collapses from weight or freeze-thaw action.

  • Mudflow: Water-saturated soil flows downhill.

  • Slump: Land slab breaks away and slips short distance.

  • Avalanche: Triggered by wind, tremors, or snow accumulation.

  • Soil solution: Dissolved soil transported by water.

Chapter 12: Rivers and Valleys

Definition of Rivers and Valleys

  • Rivers: Streams formed in upland areas as water accumulates.

  • Valleys: Low areas between hills/mountains, typically with rivers.

Drainage Patterns

  • Dendritic: Resembles leaf veins, found in uniform rock areas.

  • Trellis: Created by folding/tilting rock layers forming parallel valleys.

  • Radial: Flows from high points like cone-shaped mountains.

River Stages

Youth

  • Features rapids, waterfalls, deep V-shaped valleys.

  • Fast moving water transports material downstream.

Mature

  • Downstream lateral erosion with no mountains and meanders.

  • Flood plains formed during overflow.

Old Age

  • Extensive meandering with periodic flooding, creating oxbow lakes.

  • Well-developed river delta results.

Rejuvenated

  • Land uplifts causing a return to vertical erosion.

Erosional Action and Transportation of Rivers

Erosional Action

  • Hydraulic action: Erosion from moving water.

  • Abrasion: Sand debris abrading banks and beds.

  • Attrition: Rocks breaking into smaller pieces from collisions.

  • Corrosion: Mildly acidic water dissolving certain rocks.

Transportation Methods

  • Solution: Material dissolved and carried away.

  • Suspension: Light material suspended in water.

  • Traction: Heavy particles dragged on the bottom.

  • Saltation: Bouncing and rolling motion of particles.

Features Created by Rivers

  • Potholes: Deep holes in river beds from pebble abrasion.

  • Gorges/Canyons: Vertical erosion creating deep structures.

  • Meanders, Oxbow lakes, Levees, Dikes: Various sedimentation structures.

  • River terraces & Sand bars: Uplifted areas and debris formations.

Definition of a Delta and Types

  • Delta: Sediment deposit areas from rivers.

  • Arcuate delta: Inverted cone shape with distributaries.

  • Bird’s foot delta: Branching channels resembling a bird's foot.

  • Estuarine delta: Sediment deposited at submerged river mouths.

Chapter 13: Glaciation

Formation of Glaciers

  • Form when accumulation exceeds ablation due to various climatic factors.

  • Conditions include: cold temperatures, accumulation locations.

Types of Glaciers

Alpine (Valley) Glaciers

  • Follow river valleys, move via gravity.

  • Speed depends on accumulation vs. ablation ratios.

  • Movement creates a glacial snout.

Continental Glaciers

  • Unconfined glaciers spreading over lowlands, can exceed 1 km thick.

  • Slow movement; leave behind features like scoured bedrock when retreated.

Erosional Features of Glaciers

  • Plucking: Rocks attached to glaciers removed due to meltwater.

  • Abrasion: Scraping of surfaces by glacier debris.

  • Drift: General term for glacier-deposited material.

Types of Glacial Deposits

  • Till: Deposits remaining post-melt.

  • Outwash: Deposits from glacial meltwater.

Notable Glacial Features

  • Cirque, Tarn, Arete, Horn: Key erosional features formed by glacial actions.

  • Striations, Moraines, Recessional moraines, Eskers, Truncated spurs, Hanging valleys: Various depositional features formed during glaciation.

Benefits from Glaciation

  • Abundant freshwater availability, tourism opportunities, road construction materials.

Chapter 14: Wave Action and Coastal Landforms

Creation and Measurement of Waves

  • Waves are formed by wind friction on water.

  • Wave length: distance between crests; height: distance from trough to crest.

Types of Waves

  • Constructive waves: Gentle, build beaches by adding sand.

  • Destructive waves: Steep, cause significant erosion and loss of sand.

Coastline Erosion

Definition

  • Process where coastal features are worn down by various forces.

Causes of Coastline Erosion

  • Corrosion: Dissolution of materials in seawater.

  • Abrasion: Sediment wearing down rock surfaces.

  • Attrition: Collisions causing fracture reductions.

  • Hydraulic action: Forces from wave power breaking rocks apart.

Erosional Features Caused

  • Coastal features: caves, bays, headlands, tunnels, arches, stacks, wave-cut platforms.

Coastal Processes

  • Swash: Movement of water onto shore.

  • Backwash: Water returning to the ocean.

  • Longshore drift: Sediment movement along beaches.

Depositional Features

  • Spit, Tombolo, Estuaries, Rias, Fiords: Various depositional landforms formed by coastal processes.

Chapter 15: Groundwater

Definition and Importance

  • Groundwater: Water in the saturated zone.

  • Essential for drinking and irrigation; overuse leads to subsidence.

Effects of Groundwater Use

  • Significant subsidence in regions such as California, raising flood risks.

Landform Creation

  • Travertine terraces: Formed by hot springs.

  • Caves or caverns: Developed in limestone areas.

  • Sinkholes: Result from caverns growing larger and collapsing.

Karst Landscapes

Definition

  • Regions underlain by soluble rock like limestone, with unique features.

Features of Karst Landscapes

  • Dry valleys, streams disappearing underground, Uvalas, Poljes, Hums: Signifying unique landforms resulting from karst processes.

Chapter 16: Wind and Desert Landscapes

Definition of a Desert

  • Deserts: Areas with annual precipitation less than evaporation.

Factors Influencing Desert Formation

  • Latitude: Deserts prevalent at 30° latitude.

  • Mountain barriers: Influence rainfall patterns.

  • Cold ocean currents and land distance from water: Affect moisture levels.

Wind and Water Erosion Effects in Deserts

  • Erosion types: Suspension, saltation, deflation.

  • Creates features like badlands and blowouts.

  • Oases: Formed when aquifers feed springs.

Water Erosion in Deserts

  • Rare rain can create fast-moving water and alluvial fans.

Sand Dune Types

  • Dune migration due to wind; types include transverse, barchan, parabolic, and longitudinal dunes.

Unique Desert Landforms

  • Bajada, Wadis, Playa lakes, Canyons, Mesa, Butte: Various landscapes shaped by erosion and sedimentation in desert conditions.

  • Hamadas and Ergs: Resulting features from extensive wind erosion.