3842:278 Geomorphology

1
38/42278Geomorphology

• Topic 3 Endogenic and Climatic Effects
• Chapter 2 Ritter et al
• Chapter 3 Trenhaile

2
Primary External Controls

• Endogenic processes
• Determines lithology and structure
• resisting forces
• Climatic
• Determines temp, precip, rates, intensity
• Driving forces
• Induce threshold events

3
Endogenic Effects

• Tectonic processes that create/deform crust
• Mountian building or orogenic events
• Meso scale
• Epeirogenic processes deform the crust
• Macro scale
• Volcanic activity
• Regional scale
• Influence topographic expression

4
Tectonic Processes

• Cause changes in crustal thickness
• Result in isostatic adjustments
• Vertical movement of crust
• Slow response

5
Isostasy

• Imbalance results in isostatic anomalies
• Negative anomalies crust rises
• Positive anomalies crust subsides
• Affect PE of exogenic systems
• Base level changes
• Incision or aggradation
• Uplift normally gt denudation
• Disequilibrium or threshold

6
Glacio-isostasy

• Result of accumulation or ablation of ice
• Isostatic rebound continues
• Initially rapid (100m/ka)
• Decreasing (5m/ka)
• Total hundreds of metres
• Isostatic adjustment of sea level, base level
  drops, stream incision

7
Hot Spots

• Concentration of radioactive energy
• Thermal expansion of upper mantle
• Vertical displacement of several hundred metres

8
Tectonic Geomorphology

• Emphasis on neotectonism
• Focus on
• impacts of tectonic actvity on process and form
• What land form can tell us about tectonic
  activity
• Measurable qualities of landforms
• Type of tectonism
• Rate

9
Fault-bounded Mountains

• Mountain front sinuousity
• Ratio of curved to straight line distance
• Valley width to height ratio

10
Characteristic Landforms
11
Fault-scarp Analysis

• Erosion and deposition on scarp face
• Indicates relative age
• Est. of absolute age
• Dependent on rate of processes

12
Plate Margins

• Emergent coastlines
• Raised terrace
• Narrow continental shelf
• Coastal Cliffs
• Incised river valleys
• Submergent Coastlines
• Wide continental shelf
• Deposition
• Low, wide coastal plain

13
Plate Margins

• Emergent coastlines
• Result of sea-level drop or tectonic uplift
• If tectonic, suggests active plate margin
• Characterized by
• Raised terraces
• Narrow continental shelf
• Coastal cliffs
• Incised river valleys

14
(No Transcript)
15
Plate Margins

• Submergent coastlines
• Result of sea-level rise or tectonic subsidence
• May indicate passive plate margin
• Characterized by
• Flooded estuaries
• Coastal deposition
• Low, wide coastal plain
• Wide continental shelf

16
(No Transcript)
17
Volcanism

• Three different types of neotectonic activity
  result in distinctive landforms
• Plateaus
• Cones
• Calderas

18
Volcanism

• Plateaus
• Extrusion of low viscosity basaltic lava
• Extensive areas of overlapping flows
• From numerous fissures and vents

19
Volcanism

• Cones
• Single vent
• Shields Volcanoes
• Effusive eruptions, low viscosity magma
• Low, wide shields volcanoes
• Composite Volcanoes
• Explosive eruptions, high viscosity magma
• Steep sided

20
Volcanism

• Calderas
• Collapse of cone into magma chamber
• Large diameter (much larger than crater)
• Associated ring fractures

21
Climatic Geomorphology

• Philosophical approach to study of geomorphology
• Based on the relationship between climate and
  landform
• Certain landforms develop under particular
  climatic condition

22
Climatic Geomorphology

• Climate determines
• Rate
• Effectiveness
• . . . of geomorphic processes
• Referred to as climate-process system
• Processes that function most efficiently in any
  climate will prevail

23
(No Transcript)
24
(No Transcript)
25
Climatic Geomorphology

• BUT, landforms vary due to geographic variations
  in
• Lithology
• Structure
• Seasonality
• Changing climate (relic landforms)