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

Earth Structure

Internal Structure -- core/mantle/crust: density, composition; oceanic vs. continental crust (thickness, density & age)

Asthenosphere vs. Lithosphere

Isostasy -- Airy or Pratt

Continental Drift & Plate Tectonics

The Theory of Continental Drift -- Wegener & various lines of evidence

Sea Floor Spreading -- concept of spreading centers, deep ocean trenches/subduction zones

The Plate Tectonics Paradigm

Divergent Plate Boundaries -- spreading centers, ridges, mafic rocks, volcanism

Convergent Plate bdys -- oceanic\oceanic; oceanic\cont; cont\cont; subduction, collision, sutures, relationship to volcanism

Shear Plate bdys -- transform faults, San Andreas

General Conclusions - What does Plate Tectonics Explain?

Impact of Successive Plate Tectonic Events -- old collisions, old continents

Major Continental Features -- trailing vs leading edge

Residuals of previous plate tectonic events -- old suture zones, mountain ranges

Rift Zones

Hot Spots

Mountain Ranges & Mountain-Building:

Orogeny & Uplift

Cause of Uplift

Isostatic Equilibrium -- glacial and sediment isostatic rebound

Volcanism

Products of Volcanism

lava -- pahoehoe, aa, blocky, pillow

pyroclastics or tephra -- ash, lapilli/cinder, blocks, bombs, tuff

volatiles -- water vapor, CO2, sulfur gases, fumaroles, solfataras, geysers/hot springs

Mixtures -- other flows -- nuées ardente, lahar

Igneous Rocks of lava & tephra -- mafic to silicic: basalt/gabbro, andesite/diorite, dacite/granodiorite, rhyolite/granite. Relate to plate tectonics.

Magma types and eruptive character: most effusive basaltic to most explosive rhyolitic.

Landforms produced by volcanoes

Flood Basalts -- effusive, valley fills, plateaus

Central Vent (pipe) Eruptions and Volcanic Cones

Shield Volcanoes -- effusive

Tephra Cones

Composite Cone or Stratovolcano

Plug Dome

Craters & Calderas -- morphometry (3x)

Plutonism : Intrusive Igneous Activity

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

Chemical Weathering

Solution

Hydration

Hydrolysis

Carbonation

Oxidation

Products of Chemical Weathering

Mechanical weathering

Unloading/Dilatation/Exfoliation

Thermal expansion/contraction

Freeze/thaw ... and fissility/porosity

Crystal growth in voids

Hydration shattering/expansion weathering

Root Growth

Weathering and its Effects on Landforms

Structure -- fissility, massive rocks, granular rocks, case hardening, tafoni

Process

Time -- rate of weathering

Slopes: Mass Wasting

Slope Stability :

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

Cohesion C

effective normal stress s'

The effect of water -- Effective Normal Stress - (s') -- 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

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.

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.

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

Human impacts: of channelization, of urbanization

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, shore platforms: abrasion & solution ramps, erosional terraces, bayhead beach

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: transverse, barchan, linear/longitudinal/seif, star, parabolic ... slipoff slope, saltating/creep slope

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.