Geomorphology: Landforms, Processes, and Coastal Features
Sand Dune Types
- Barchan: Small sand dunes on flat terrain.
- Transverse: Large sand dunes on flat terrain.
- Barchanoid: Crescent-shaped dunes.
- Yardangs: Low ridges carved by wind in flat deserts.
Mass Movement Causes
- Slope angle exceeds the angle of repose.
- Uplift changes the slope angle.
- Removing material from the bottom or adding to the top.
Types of Mass Movement
- Slide: Movement on a basal slip surface (planar or curved).
- Slump: Smaller slides caused by gravity on well-defined surfaces.
- Flow: Movement as a viscous fluid.
- Earthflow: Viscous fluid movement, topsoil may remain intact.
- Debris flow: More fluid movement with more water than earthflows.
Big basin = higher discharge, steeper slopes
Coastal Features on Active Margins
- Sea stacks, arches, pocket beaches, volcanic arcs, trenches, cliffs, narrow continental shelf, terraces, hot spots, mid-ocean ridges, turbidity currents, seamounts, spits.
Coastal Features on Passive Margins
- Sandy beaches, broad continental shelf, submarine slumping, abyssal plains, marshes/mangroves, barrier islands, estuaries/deltas, reefs.
Failure Type | Type of Material | Type of Motion | Rate of Motion |
Rock Fall | Rocky fragments | Vertical or near-vertical fall (plus bouncing) | Very fast (>10s m/s) |
Rock slide | A large rock body | Motion as a unit along a planar surface (translational sliding) | Typically very slow (mm/y to cm/y), some faster |
Rock avalanche | A large rock body that slides and then breaks into small fragments | Flow (at high speeds, mass suspended on air) | Very fast (>10s m/s) |
Creep or solifluction | Soil or overburden, sometimes with ice | Flow (though sliding may occur) | Very slow (mm/y to cm/y) |
Slump | Thick deposits (10s of m) of unconsolidated sediment | Motion as a unit along a curved surface (rotational sliding) | Slow (cm/y to m/y) |
Mudflow | Loose sediment with silt and clay | Flow (sediment and water down a channel) | Moderate to fast (cm/s to m/s) |
Debris Flow | Sand, gravel, and larger fragments | Flow (similar to mudflow, but faster) | Fast (m/s) |
Geological Features
- Mid-ocean ridge: Upwelling of magma associated with seafloor spreading.
- Reef: Offshore of tropical areas.
- Mangrove: Tropical trees on the coast.
- Turbidity Current: Rapid downhill flow of water with high sediment.
- Cliffs: Steep rock faces.
- Sea arches: Natural rock arches formed by erosion.
- Sea stacks: Isolated rock formations in the sea.
- Salt marsh: Coastal wetlands.
- Abyssal plain: Flat region of the ocean floor.
- Seamount: Underwater mountain.
- Hot-spot: Builds chains of oceanic islands.
- Active margin: Tectonically active coast.
- Passive margin: Broad continental shelf develops.
- Beach: Sandy shore.
- Barrier: Island parallel to the coast.
- Spit: Deposition bar off coast/lake shore.
- Estuary: Tidal mouth of a large river.
- Delta: Deposition of silt from river water.
Tectonic Processes
- Brittle deformation: Rocks crack in response to stress.
- Ductile (plastic) deformation: Rocks bend in response to stress.
- Orogeny: Mountain range formation.
- Continental Crust: Less dense crust.
- Mountainbuilding: Process of mountain formation.
- Subduction: One crust under another.
- Folding: Bending of rock layers.
- Faulting: Fracturing of rock layers.
- Foliation: Alignment of minerals in layers.
- Joints: Cracks in rock.
- Veins: Mineral deposits in rock fractures.
- Anticlines: Upward folds in rock layers.
- Synclines: Downward folds in rock layers.
Water Systems
- Source Area: Where water comes from.
- Watershed: Area of land separating water flow.
- Lake: Large body of water.
- Glacier: Large mass of ice.
- Rapids: Fast-flowing water.
- Relief: Variation in elevation.
- Topography: Forms and features of land.
- Waterfall: Water falling over a resistant rock layer.
- Braided River: High energy river with multiple channels.
- Braided Stream: Steep stream with coarse sediments.
- Meandering stream: Low energy stream with fine sediments.
- Meandering river: Low energy river with fine sediments.
- Floodplain: Ground around a river that floods.
- Erosion: Where sediment comes from.
- Deposition: Where sediment ends up.
- Terrace: Step-like landform.
- Bank: Side of a river.
- Point bar: Deposition on the inside of a river bend.
- Yazoo: Tributary stream parallel to a large river.
- Oxbow lake: Curved lake formed from a river meander.
- Levee: Embankment to prevent river overflow.
- Swamp: Wetland with trees.
- Bar: Sediment deposit in a river or ocean.
- Delta: Landform at the mouth of a river.
- Tidal flat: Coastal wetlands formed by deposits.
- Drainage basin: Area drained by a stream and its tributaries.
Exam Topics
- Oceans & Coasts: Determine margin type (active or passive) based on coastal features.
- Tectonic Landforms: Identify plastic (ductile) and brittle deformation from pictures.
- Deserts and Glaciers: Determine if a feature was created by erosion or deposition.
Erosion and Deposition
- Erosion: Movement by wind or water.
- Deposition: Sediment carried by wind, water, sea, or ice.
- Glacier: Large mass of ice from year-round snow.