⛏️Intro to Geology Unit 12 – Surficial Processes and Landforms

Key Concepts and Definitions

• Surficial processes encompass the physical, chemical, and biological processes that shape Earth's surface
• Landforms refer to the physical features on Earth's surface created by geologic processes (mountains, valleys, plateaus)
• Weathering breaks down rocks and minerals at or near Earth's surface through physical, chemical, and biological processes
• Erosion involves the removal and transport of weathered material by agents such as water, wind, ice, and gravity
• Deposition occurs when eroded sediments are deposited and accumulate in a new location
• Sediment load describes the amount of solid material carried by a stream or river and consists of dissolved, suspended, and bedload sediments
• Topography refers to the shape and features of Earth's surface, including elevation, slope, and orientation
  • Influences the distribution and movement of water, sediment, and other materials across the landscape

Weathering and Erosion Basics

• Physical weathering involves the breakdown of rocks and minerals through mechanical processes without changing their chemical composition
  • Includes frost wedging, thermal expansion and contraction, and abrasion
• Chemical weathering alters the chemical composition of rocks and minerals through reactions with water, air, and organic compounds
  • Common processes include dissolution, oxidation, and hydrolysis
• Biological weathering occurs when living organisms contribute to the breakdown of rocks and minerals
  • Examples include root wedging, burrowing animals, and microbial activity
• Differential weathering results in uneven weathering of rocks due to variations in mineral composition, structure, and exposure
• Erosion rates depend on factors such as climate, topography, vegetation cover, and rock type
• Mass wasting involves the downslope movement of rock, soil, and debris under the influence of gravity
  • Includes landslides, rockfalls, and debris flows
• Soil formation results from the complex interaction of weathering, erosion, and biological processes over time

Types of Landforms

• Mountains form through tectonic processes (plate collisions, volcanic activity) or differential erosion of resistant rock layers
• Plateaus are elevated, flat-topped landforms often formed by the uplift and erosion of horizontal rock strata
• Plains are extensive, relatively flat areas that can be formed by deposition of sediments or erosion of softer rock layers
• Valleys are low-lying areas between hills or mountains, typically formed by fluvial erosion or glacial processes
• Canyons are deep, steep-sided valleys often carved by rivers over long periods of time (Grand Canyon)
• Deltas are depositional features formed where rivers enter a larger body of water and deposit their sediment load
• Beaches are accumulations of sand, gravel, or other sediments along the shoreline of oceans, lakes, or rivers
  • Shaped by waves, tides, and currents

Fluvial Processes and Features

• Fluvial processes involve the erosion, transport, and deposition of sediments by running water in streams and rivers
• Drainage basins are areas of land where all surface water and groundwater drain into a common outlet (river, lake, ocean)
• Stream gradient refers to the slope of a stream channel and influences the velocity and erosive power of the water
• Discharge is the volume of water flowing through a stream channel per unit time and varies with precipitation and snowmelt
• Sediment transport in streams occurs as dissolved load, suspended load, and bedload, depending on particle size and water velocity
• Erosional features in fluvial environments include V-shaped valleys, waterfalls, and rapids
• Depositional features in fluvial environments include alluvial fans, floodplains, and river terraces
  • Alluvial fans form where steep mountain streams enter a plain, depositing sediments in a fan-shaped pattern

Coastal Processes and Formations

• Coastal processes are driven by the interaction of waves, tides, and currents with the shoreline
• Waves are generated by wind blowing over the surface of the water and can cause erosion, transport, and deposition of sediments
• Longshore currents transport sediments parallel to the shoreline, resulting in the formation of spits and barrier islands
• Tides are the regular rise and fall of sea level caused by the gravitational pull of the moon and sun
  • Tidal range influences the extent of intertidal zones and the development of tidal flats and salt marshes
• Coastal erosion can lead to the formation of cliffs, sea arches, and sea stacks
• Depositional features in coastal environments include beaches, spits, barrier islands, and tidal flats
• Sea level changes due to climate fluctuations or tectonic activity can significantly impact coastal landforms and ecosystems

Glacial and Periglacial Landscapes

• Glaciers are large masses of ice that form in areas where snow accumulation exceeds melting over many years
• Glacial erosion occurs through plucking (removal of rock fragments) and abrasion (grinding action of debris-laden ice)
• Erosional features created by glaciers include U-shaped valleys, cirques, horns, and arêtes
• Depositional features associated with glaciers include moraines (lateral, medial, terminal), drumlins, and eskers
  • Moraines are ridges of debris deposited along the sides, front, or center of a glacier
• Outwash plains form when glacial meltwater deposits sediments beyond the glacier's terminus
• Periglacial landscapes develop in cold, non-glacial environments where freeze-thaw cycles and permafrost influence landforms
• Patterned ground, such as polygonal networks and stone circles, form through the sorting of sediments by freeze-thaw processes
• Thermokarst topography develops when permafrost thaws, leading to the formation of sinkholes, lakes, and irregular terrain

Aeolian (Wind-Driven) Processes

• Aeolian processes involve the erosion, transport, and deposition of sediments by wind
• Wind erosion is most effective in arid and semi-arid regions with sparse vegetation cover and abundant loose sediments
• Deflation is the removal of fine sediments by wind, leaving behind a rocky surface called desert pavement
• Abrasion occurs when wind-blown particles impact and erode rock surfaces, creating features like ventifacts and yardangs
• Sand dunes are depositional features formed by the accumulation of wind-blown sand
  • Dune types include barchan, transverse, linear, and star dunes, depending on wind direction and sediment supply
• Loess is a fine-grained, wind-blown sediment that can form thick, fertile deposits in areas downwind of glacial or fluvial sediment sources
• Dust storms and sandstorms are significant events in arid regions that can transport sediments over long distances

Human Impact on Landforms

• Urbanization and infrastructure development can alter natural drainage patterns, increase erosion, and modify topography
• Agriculture practices such as deforestation, overgrazing, and tillage can accelerate soil erosion and lead to land degradation
• Dam construction and river channelization can disrupt sediment transport, alter fluvial landforms, and impact downstream ecosystems
• Mining activities, including surface mining and mountaintop removal, can drastically reshape landscapes and increase erosion rates
• Coastal development and engineering structures (seawalls, groins) can interfere with natural coastal processes and exacerbate erosion
• Land reclamation projects, such as the creation of artificial islands or the draining of wetlands, can permanently alter coastal and fluvial landforms
• Climate change, influenced by human activities, can lead to changes in precipitation patterns, sea level rise, and the intensity of geomorphic processes
  • Resulting in the modification of landforms and the vulnerability of human settlements and infrastructure