🧭Physical Geography Unit 5 – Landforms and Geomorphology

Key Concepts and Terminology

• Geomorphology studies the formation and evolution of landforms on Earth's surface
• Endogenic processes originate from within the Earth (plate tectonics, volcanism)
• Exogenic processes originate from outside the Earth's surface (weathering, erosion, deposition)
• Topography refers to the shape and features of the Earth's surface
• Geomorphic agents include water, wind, ice, and gravity that shape the Earth's surface
• Landforms are natural physical features on the Earth's surface (mountains, valleys, plateaus)
• Weathering breaks down rocks and minerals through physical, chemical, and biological processes
• Erosion involves the removal and transportation of weathered material by geomorphic agents

Earth's Structure and Plate Tectonics

• Earth's interior consists of the crust, mantle, outer core, and inner core
  • Crust is the outermost layer composed of continental and oceanic crust
  • Mantle is the layer beneath the crust, composed of hot, dense rock
  • Outer core is a liquid layer composed primarily of iron and nickel
  • Inner core is a solid layer at the center of the Earth, composed of iron and nickel
• Plate tectonics is the theory that Earth's lithosphere is divided into large, rigid plates that move and interact
• Convergent boundaries occur where plates collide, causing subduction, mountain building, and volcanism (Andes Mountains)
• Divergent boundaries occur where plates move apart, causing seafloor spreading and rift valleys (Mid-Atlantic Ridge)
• Transform boundaries occur where plates slide past each other, causing earthquakes (San Andreas Fault)
• Hotspots are stationary mantle plumes that cause volcanic activity (Hawaiian Islands)

Types of Landforms

• Mountains are landforms with steep slopes and high elevations, formed by tectonic activity, volcanism, or erosion
  • Fold mountains form when tectonic plates collide and compress sedimentary layers (Himalayas)
  • Fault-block mountains form when tectonic forces cause blocks of crust to uplift and tilt (Sierra Nevada)
  • Volcanic mountains form from the accumulation of lava and volcanic debris (Mount Fuji)
• Plateaus are elevated, flat-topped landforms formed by tectonic uplift or erosion-resistant rock layers (Colorado Plateau)
• Plains are flat, low-lying landforms formed by sediment deposition or erosion (Great Plains)
• Valleys are elongated depressions in the Earth's surface, typically formed by fluvial erosion (Grand Canyon)
• Canyons are deep, narrow valleys with steep walls, often carved by rivers (Yarlung Tsangpo Grand Canyon)
• Deltas are landforms formed at the mouth of a river where sediment is deposited (Mississippi River Delta)

Weathering and Erosion Processes

• Physical weathering involves the breakdown of rocks through mechanical processes without changing their chemical composition
  • Frost wedging occurs when water freezes and expands in rock crevices, causing the rock to break apart
  • Thermal expansion and contraction cause rocks to crack due to temperature changes
  • Exfoliation is the peeling off of rock layers due to pressure release
• Chemical weathering involves the breakdown of rocks through chemical reactions, altering their composition
  • Carbonation occurs when carbon dioxide dissolves in water, forming carbonic acid that reacts with rocks
  • Hydrolysis is the reaction between water and minerals, causing the formation of clay minerals
  • Oxidation occurs when oxygen reacts with minerals, often forming rust-colored iron oxides
• Biological weathering involves the breakdown of rocks by living organisms
  • Plant roots can grow into rock crevices, causing physical weathering
  • Lichen and moss secrete acids that contribute to chemical weathering
• Erosion is the removal and transportation of weathered material by geomorphic agents
  • Water erosion includes sheet erosion, rill erosion, and gully erosion
  • Wind erosion occurs in arid environments, creating features like sand dunes and yardangs
  • Glacial erosion involves the scouring and plucking of bedrock by moving ice

Fluvial Systems and Landforms

• Fluvial systems involve the movement of water and sediment through rivers and streams
• Drainage basins are areas of land where all water drains into a common outlet (Mississippi River Basin)
• Stream channels are the pathways through which water and sediment flow
  • Straight channels have a linear course and are relatively rare in nature
  • Meandering channels have a sinuous course with alternating pools and riffles
  • Braided channels consist of multiple intertwined channels separated by sediment bars
• Fluvial erosion processes include abrasion, hydraulic action, and solution
• Fluvial deposition processes include alluvial fans, floodplains, and river terraces
• Waterfalls and rapids form where resistant rock layers are exposed in a river's course (Niagara Falls)
• Oxbow lakes form when meanders are cut off from the main river channel

Coastal Geomorphology

• Coastal geomorphology studies the formation and evolution of landforms along the interface between land and sea
• Waves are the primary geomorphic agent in coastal environments, generated by wind blowing over water
• Tides are the rise and fall of sea level caused by the gravitational pull of the moon and sun
• Coastal erosion processes include abrasion, hydraulic action, and solution
  • Abrasion occurs when waves hurl sediment against cliffs and rocks, causing erosion
  • Hydraulic action is the force of waves striking and compressing air in rock crevices, causing erosion
  • Solution involves the dissolving of minerals in seawater, particularly in limestone coasts
• Coastal deposition landforms include beaches, spits, and barrier islands
  • Beaches are accumulations of sand or gravel along the shoreline
  • Spits are elongated ridges of sand that extend from the shore into the sea (Farewell Spit, New Zealand)
  • Barrier islands are elongated offshore islands that run parallel to the coast (Outer Banks, North Carolina)
• Sea cliffs and wave-cut platforms form through coastal erosion processes
• Estuaries are partially enclosed coastal bodies of water where freshwater and saltwater mix (Chesapeake Bay)

Glacial and Periglacial Processes

• Glaciers are large masses of ice that move under the influence of gravity
  • Alpine glaciers form in mountainous regions and flow through valleys (Aletsch Glacier, Switzerland)
  • Continental glaciers are large ice sheets that cover vast areas of land (Antarctic Ice Sheet)
• Glacial erosion processes include abrasion, plucking, and freeze-thaw weathering
  • Abrasion occurs when rocks embedded in the base of a glacier scrape against the underlying bedrock
  • Plucking involves the removal of large chunks of bedrock by the glacier
  • Freeze-thaw weathering occurs when water in rock crevices freezes and expands, breaking the rock apart
• Glacial deposition landforms include moraines, drumlins, and eskers
  • Moraines are accumulations of glacial debris deposited along the edges or at the terminus of a glacier
  • Drumlins are elongated, teardrop-shaped hills formed by glacial deposition
  • Eskers are long, winding ridges of sand and gravel deposited by meltwater streams within or beneath a glacier
• Periglacial processes occur in cold, non-glacial environments where freezing and thawing of water in soil and rocks occur
  • Permafrost is ground that remains frozen for at least two consecutive years
  • Patterned ground, such as polygonal networks and stone circles, form through frost action and sorting of sediments
  • Solifluction is the slow downslope movement of water-saturated soil in periglacial environments

Human Impact on Landforms

• Urbanization and infrastructure development alter natural landforms and drainage patterns
  • Construction of roads, buildings, and parking lots increases impervious surfaces, leading to increased surface runoff and erosion
  • Channelization of rivers and streams can increase flood risk and alter riparian habitats
• Agriculture and deforestation can accelerate soil erosion and alter soil properties
  • Removal of natural vegetation exposes soil to erosion by wind and water
  • Overgrazing can lead to soil compaction and reduced infiltration, increasing surface runoff and erosion
• Mining activities can drastically alter landforms and impact local ecosystems
  • Strip mining removes large volumes of rock and soil, creating artificial landforms and exposing mine tailings
  • Mountaintop removal mining in the Appalachian Mountains has led to the destruction of mountain peaks and burial of valleys
• Coastal development and engineering structures can disrupt natural coastal processes
  • Construction of seawalls, groins, and jetties can alter sediment transport and cause downdrift erosion
  • Dredging of channels and harbors can change tidal flow patterns and affect coastal habitats
• Climate change is influencing geomorphic processes and landform evolution
  • Rising sea levels due to global warming are increasing coastal erosion and inundation
  • Changing precipitation patterns and extreme weather events can alter erosion rates and sediment transport
  • Melting glaciers and permafrost are changing alpine and periglacial landscapes