Ch. 03 Flashcards
The process by which land areas are reduced and shaped through weathering and erosion.
Denudation
The breakdown of minerals into new compounds through chemical agents such as acids in the air, rain, and river water.
Chemical Weathering
The breakdown of rocks into smaller particles through temperature changes, impact from raindrops, and abrasion from wind-carried mineral particles.
Mechanical Weathering
Mechanical and chemical changes to the ground caused by the activities of plants, animals, and microbial action.
Biological Weathering
The process of removing weathered material (detritus) from its source area by agents like rivers, wind, moving ice, and water waves.
Erosion
The laying down of transported detritus to form features such as deltas, beaches, screes, and sand dunes.
Deposition
What are the (7) Chemical Weathering Processes
Solution
Oxidation
Reduction
Hydration
Hydrolysis
Leaching
Cation Exchange
A vertical sequence of layers from topsoil to unweathered rock, consisting of A-horizon (soil), B-horizon (sub-soil), and C-horizon (unweathered rock).
Soil Profile
Landforms resulting from chemical weathering of limestone, characterized by caves, sinkholes, and underground drainage systems.
Karst Topography
Formations in caves resulting from the deposition of calcium carbonate due to evaporation of water charged with calcium bicarbonate.
Stalactites and Stalagmites
Upstanding masses of solid granite preserved due to wider spacing of joints, contrasting with adjacent rocks more extensively denuded by weathering.
Granite Tors
Describe Weathering in Different Climates
Wet climates: Deep weathering due to vegetation, heavy rainfall.
Dry climates: Superficial weathering, mechanical processes dominant.
Weathering Agents
Rainwater
Frost
Wind
Temperature changes
Abrasion from mineral particles
Biological activity (plants, animals, microbes)
Types of Weathering
Physical and Chemical
Factors Influencing Weathering Rates
Presence of water
Climate (wet vs. dry)
Presence of vegetation
Type of rock and minerals present
Temperature variations
Signs of Chemical Weathering
Formation of solution hollows on limestone surfaces
Widening of vertical joints in rocks due to solution
Formation of swallow holes and underground caverns in limestone areas
Development of karst topography features like sinkholes and disappearing streams
Role of Vegetation in Weathering
Production of CO2 in the root zone, enhancing chemical weathering
Roots penetrating rocks, breaking them apart
Increased acidity of soil due to root activity, aiding chemical reactions
Effects of Weathering on Soil
Formation of soil horizons (A-horizon, B-horizon, C-horizon)
Porosity and compressibility of soil
Nutrient content and organic matter accumulation
Examples of Landforms Created by Weathering and Erosion
River valleys and canyons
Coastal cliffs and sea stacks
Glacial valleys and moraines
Alluvial plains and floodplains
Human Impacts on Weathering and Erosion:
Deforestation leading to increased erosion rates
Urbanization altering natural drainage patterns
Agriculture practices affecting soil erosion
Climate change influencing weathering rates and erosion patterns
Mechanical Weathering Processes
Unloading
Loading
Thermal Loading
Wetting and Drying
Crystallization
Pneumatic Loading
Reduction of vertical load by erosion, leading to vertical expansion and the formation of sheet-like rock structures.
Commonly observed in igneous rocks like granite, resulting in sheet-jointing.
Unloading
Repeated freezing and thawing of water in pores and fractures of rocks.
Frost Action
Permanently frozen ground, prevalent in cold climates, especially within the Arctic Circle.
Permafrost
Shallow zone thawing annually during milder seasons.
Active layer
Slow movement of surface material over frozen ground due to repeated freezing and thawing.
Solifluction
Formation of segregated ice layers at shallow depths in soil.
Frost-Heaving
Weathering process in hot climates, involving the expansion and contraction of rocks due to temperature changes.
Insolation
Outer layers of rock pull away from cooler layers, resulting in flake and slab detachment.
Exfoliation
Weathering effects attributed to plants and animals.
Biotic Weathering
Roots of plants penetrate cracks in rocks, wedging apart crack walls and hastening mechanical break-up.
Mechanical Break-up by Plants
Relationship Between Soils and Weathering
Soils are classified according to climatic zones, reflecting latitude.
Soils and weathering processes exhibit a basic relationship influenced by climate.
Found in South America, Central and Southern Africa, India, Sri Lanka, Southeast Asia, East Indies, and Australia.
Rich in aluminum and iron oxides, formed under previous climatic conditions.
Laterite Deposits
what are agents of erosion?
Rivers, wind, moving ice, and water waves
Agents of transport, carrying material in suspension and re-depositing downstream, forming levees and flood plains.
River Erosion
Zig-zag courses with overlapping spurs
Youthful Valleys
occurs when a river’s cutting power is revived
Rejuvenation
Break in slope at the junction of old and new river courses.
Nick-point
Erosion in alternating hard and soft rock layers results in ________
Terraced Slopes
Flat-topped hill with a hard rock cap.
Mesa
These form where rivers flow over rocks of differing hardness.
Waterfalls and Rapids
between Lake Erie and Lake Ontario, drops 55 meters over hard limestone.
Niagara Falls
formed by youthful streams eroding rapidly.
Gorges
The Colorado River carved _________ over 400 km in length and about 2 km deep.
Grand Canyon
occurs as rivers swing from side to side
Meandering Rivers
Meandering rivers can create _________ when loops are cut off during floods.
Oxbow Lakes
Meanders can become ________ when rivers gain fresh energy and downcut.
Incised Meanders
Deposits laid down by rivers, including fine materials like silt and mud, and coarser sand and gravel.
Alluvium
form where rivers enter bodies of water and deposit sediment.
Deltas
occurs on the land margin through their impact and the debris they carry, especially during storms
Wave erosion