Geog 312 -- Geography of Landforms -- Study Guide

The following is an outline of the lectures, for the entire semester. There are three exams, distributed roughly equally with one third of the material on each exam. The breaks between material covered by each exam will be announced in class prior to each exam. Know processes, landform features, and geographic examples.

Introduction -- The Science of Geomorphology

• W. M. Davis's Structure, Process, & Stage/Time
• Geomorphic Scales
• Endogenic vs. Exogenic processes

Megageomorphology & Endogenic Processes

Continental Drift & Plate Tectonics

Mountain Ranges & Mountain-Building:

Volcanism

Products of Volcanism

Landforms produced by volcanoes

Flood Basalts -- effusive, valley fills, plateaus like Columbia, Modoc, Deccan

Central Vent (pipe) Eruptions and Volcanic Cones

• Shield Volcanoes -- effusive, Mauna Loa
• Tephra Cones (Cinder Cone)
• Composite Cone or Stratovolcano (Shasta, etc.)
• Plug Dome (Lassen, etc.)

Craters & Calderas -- morphometry (3x)

Plutonism : Intrusive Igneous Activity

• Rock Types (see above)
• Intrusive Forms -- sills, dikes, laccoliths, batholiths

Volcanic Landscape Evolution

• relationship of extrusive and intrusive forms before and after volcanism
• Inverted topography

Rocks

Sedimentary

• origin, type of sediments, mineralogy of rock or cement, resistance to weathering)
• clastic: conglomerate, sandstone, siltstone, mudstone, shale
• chemical (& biogenic): rock salt; gypsum; carbonates: limestone & dolomite; chert-flint-jasper; coal

Metamorphic Rocks: (origin, original rock, resistance to weathering): slate, schist, gneiss, marble, quartzite

Weathering

Slopes: Mass Wasting

• Slope Stability :

  • Shear Strength/Shear Stress = Safety Factor
  • Shear Stress = Wsinθ or understand it graphically, or even just the general relation to slope angle)
  • Shear Strength = C + σ' F  (Coulomb equation)

    • Cohesion C

    • effective normal stress σ'

      • The effect of water -- Effective Normal Stress - σ') -- increases if undersaturated (negative pore pressure, or tension), decreases if saturated (positive pore pressure...particles float a bit, thus grip less).  Effective normal stress increases with decreasing pore pressure.
    • F : angle of internal friction
      • like slope percent (rise/run), but 1.0 means 100%
      • same as angle of repose if dry & no cohesion
  • Simple Model - forces acting on a particle on a slope
    • Stresses acting on Layers of Soil & Rock -- Deriving Normal Stress
    • Factors which can alter slope stability -- weathering, joint spacing, dip vs. slope angle, water

• Types of Mass Movements

  • Fall (and talus cone)
  • Topple
  • Slide
    • Translational Slides -- debris slide
    • Rotational Slides -- soil slip or slump & earthflow
  • Creep -- soil & rock; speeds, needle ice
  • Flows -- solifluction, gelifluction, debris flow, earth flow, mud flow, lahar, avalanche

  Management considerations

  Note: Be prepared to produce labeled diagrams of landforms and processes on the test.

  Slopes & the Drainage Basin: Water Erosion

  • Overland Flow (Hortonian & Saturation) processes -- rainsplash, sheetwash, rill, gully
  • Effectiveness of Water erosion
    • laminar vs. turbulent flow conditions
    • suspension, traction, saltation, solution
    • Throughflow/Interflow - subsurface erosion -- & piping ; saturation overland flow
  • Slope Analysis
    • convex vs. concave slopes -- and creep vs. slopewash debate -- why downslope more concave than upslope? (saturation overland flow)
    • Hypothetical 9-unit slope model (interfluve, seepage slope, convex creep slope, fall face, transportational midslope, colluvial footslope, alluvial toeslope, channel bank, channel bed)
    • Three-dimensional analysis

  Drainage Basin

  as relates to slopes, pour point, catchment area, tributaries, discharge, velocity, runoff, drainage divide, network: stream order (Strahler) and Shreve link magnitude, drainage density, badlands

  Fluvial Processes & Landforms

  Fluvial processes

  suspension, traction, saltation, solution, bed load + saltation + suspended load = solid load, dissolved load, capacity, competence; Hjulstrom diagram: erosion velocity, settling velocity, relationship with type of load (Why do silts and clays dominate suspended load, and gravels+ dominate bed load?  Contrast sand and clay); frequency & magnitude concept -- effective discharge. Significance of competence & capacity on alluvial fans and deltas.

  Perspectives on studying streams

  • Channel Cross-Section: channel response: stream power f(QS) scour & fill, Principle of Continuity:  Discharge (volume/time) = AV ; Impact on W, D, & V of change in discharge, relationship to meandering, braided, concrete and bedrock channels.  Effective Q. "Lane Equation" for stream channel equilibrium Qs * D50 prop to Qw * S, with relative increases leading to aggradation or degradation
  • Longitudinal Profile: meaning of, relationship with sediment load, discharge, base level. Concept of Grade; Base Level.  Knickpoint (resistant & headcut types); stream terraces (old flood plains); headward erosion, caprocks, sapping, plunge pools, riffle/pool sequences & effective Q/velocity reversal.
  • River Channel Habit: causes and characteristics of straight (structural control), sinuous, meandering, braided, anastomosing.  Features such as riffles, pools, cut bank, point bar, thalweg, rapids.  Consider suspended vs bed load, lateral migration, bank stability, vegetation control.  Landforms:  point bar, flood plain, oxbow lake, meander scar, natural levee, meander cutoff, stream terraces, entrenched meanders, alluvial fan, delta, lakes

  Historical development of stream valleys

  • youth, maturity, old age – characteristics of valley form, flood plain development, causes of rejuvenation, entrenched meanders.

  Coastal Processes & Landforms

  Processes that affect coastal zone

  • waves, tide, currents, rivers, mass wasting, glacial, wind
  • Characteristices of waves swell (velocity, duration, fetch), tsunami, storm surge, local wind waves, wave refraction, shoaling
  • shore zones: offshore, nearshore, foreshore, backshore; wave and tidal influences
  • wave action: hydraulic action - compression/decompression, swash/backwash, corrasion vs. corrosion
  • types of coastlines: emergent vs. submergent; progradation, retrogradation; transgression/regression; uplift & subsidence
  • Erosion processes: wave action, mass wasting; current action: tidal, longshore, rip, stream currents

  Coastal Landforms

  • Cliff erosion landforms:result from uplift coupled with strong wave action -- potential for retrograde erosion > deposition; wave-cut notch, sea caves, headlands, sea stacks, sea arches, shore platforms: abrasion & solution ramps, erosional terraces, bayhead beach, zetaform coast
  • transportational & depositional processes and landforms: beach, coastal sediments, longshore drift (beach drift + longshore current) and relation to oblique wave approach, berm, bar, spit, tombolo, bay-mouth bar
  • progradational shoreline features: depositional terrace, barrier island, lagoons (compared with bays & estuaries)
  • River outlet features: deltas, estuaries, tidal features
  • Organic buildups: reefs: fringing, barrier, atoll
  • human impacts: polders, dikes, dams, breakwaters/jetties, dredging, groynes

  Wind Processes, Features, and Landforms

  • gravels + : abrasion, ventifacts, lag deposits, desert surfaces: reg (including desert pavement), hammada
  • sands : saltation, suction from winds, surface creep, ripples
  • silt and clay : suspension (dust devils, dust storms), loess
  • Landforms: deflation hollows, yardangs, erg, embryo dunes, dunes:
    • dune types: transverse, barchan, linear/longitudinal/seif, star, parabolic
    • dune features (especially of barchan): saltating/creep slope with ripples, and slipface (like a talus)

  Structures 

  • strata: description of strata and faults: dip & strike; detection on topographic/geologic maps
  • folds: anticlines, synclines, monoclines, homoclines, recumbent; axis, plunging;
  • resulting landforms: valleys & ridges (anticlinal, synclinal, homoclinal), zigzag ridges, relation to jointing, beds of contrasting erosional resistance
  • faults: normal dip-slip, thrust, strike-slip; relation to crustal extension or compression
  • landforms: block mountains, triangular facets, pressure ridges, sag ponds

  Structural Control of Fluvial Landforms

  • stream histories and structural control: antecedent, consequent, subsequent, superposed
  • drainage patterns: dendritic, trellis, rectangular, radial, centripetal, parallel, deranged (multibasinal)
  • Stream Capture/Piracy : Elbow of Capture, overfit captor stream, underfit beheaded stream, relationship to structural control & time & stream power

  Karst

  • karst rocks: characteristics of, relation to climate
  • karst processes: carbonation-solution (significance of CO₂ from soil atmosphere, solution vs. precipitation processes), fluvial, mass wasting; relation to climate (tropical vs. midlatitude karst); carbonate speleothems and tufa; erosion rates (derived average surface lowering)
  • karst hydrology & cavern development: groundwater zones and theories of cavern development—Darcy flow lines; deep phreatic, vadose, and water table caves; invasion caves, paraphreatic caves; significance of mixing corrosion, corrosion & corrasion; single vs. multiple aquifer theories
  • karst surface landforms: karren, doline (solutional, suffosion-subsidence, collapse, subjacent karst collapse), uvala, polje, tower, cockpit; valley karst: blind valley, dry valley, steephead

  Climatic Morphogenesis

  • Tropical Wet: corrosion/corrasion; waterfalls; depth of weathering; CO₂ solubility; organic acids; steep slopes
  • Wet/Dry: seasonally fluctuating watertable; laterites, ferricrete, duricrusts; inselbergs: bornhardts, kastle-kopjes, tors; basal surface of weathering
  • Arid: corrasion/corrosion; flashiness; fluvial still dominates, but arroyos/wadis common, with influent streams; wind relatively significant; pediments; alluvial fans & bajadas
  • Climatic Change
    • Quaternary Period, Pleistocene & Holocene Epochs, Glacials (Wisconsinan, Illinoian, Kansan, Nebraskan) & Interglacials; Causes of climatic changes (astronomical, etc.)

  Glacial Processes & Landforms

  • Ice Ages on our Planet: extent of ice today and during glacials, how the recent Holocene period is an interglacial of the Quaternary
  • Glaciology: Snow, firn, ice, mass budget, ablation and accumulation, zones of ablation/accumulation, equilibrium line, flow lines;
  • Glacial movement: plastic deformation, basal slip, regelation, fracturing; relative speed and relation to temperature (slower plastic deformation with cold-base "Polar" glaciers; faster basal slip with warm-base "Temperate" glaciers)
  • Types of glaciers: cirques, alpine and outlet valley glaciers, highland ice cap, piedmont glaciers
  • Features of glaciers: nunataks, crevasse systems, moraines (lateral, medial, interlobate, ablation/ground moraine, end moraine); Drainage systems: supra-, en-, sub-glacial streams, moulins, springs
  • Glacial Erosion Processes: abrasion (striation, groove, polish), plucking, subglacial meltwater erosion (potholes, channels);
  • Erosional Glacial Features & Landforms (especially alpine): trough, cirque, arete, horn, rock step, col, hanging valley/trough, roche moutonnee; tarns, paternoster lakes, trough lake, fjords
  • Glacial Depositional Features & Landforms (alpine & continental): erratics, till, stratified drift, end moraines: terminal & recessional, drumlins, esker, kame, kettle, outwash plain/valley trains - braided channel habit

  Note: Be prepared to produce labelled diagrams of landforms and processes on the test.