GES 121 - Geological Basis of Physical Geography

Two Roles of the Crust

1. Active: endogenic forces(from within)/geomorphic processes
   create landforms and influence the distribution of living things, including humans, since these processes are natural hazards
   - Tectonism

1. Passive: Resisting framework, exogenic forces (sun)
   structure and composition of rock at earth’s surface influence weathering and erosion, movement of water, and physical/chemical properties of soil; spatial variation in these properties is significant and creates landscapes.
   - Geomorphology

Tectonism (Active; Role of the Crust)

structural and structurally controlled landscapes, represents difference in patterns on the landscape

• mountain building or folding

(other active stuff)

diastrophism: displacement and deformation of the crust

faulting: displacement of rock along a fracture in the crust (produces earthquakes)

folding: plastic deformation (bending) of rock

volcanism: the extrusion of magma, rock fragments, and gases through openings int he crust

plate tectonics: the global model of crustal deformation, displacement, and volcanism

Geomorphology (Passive; Role of the Crust)

the study of change of the shape of the earth and its present shape

Geomorphic Agents:

• water - fluvial processes

• wind - aeolian processes

• oceanic water and wind - coastal processes

• ice - glacial processes

Geomorphic Continuum

• erosion (wear down by agents) → transport (usually by agents also) → deposition (perhaps change in base level (lake drained) or tectonic uplift (relief))

• process repeats

Geomorphic Agents

water - fluvial processes

• power of running water, geomorphic substance because of its density (1000kg/m³)

wind - aeolian processes

• (1kg/m³) especially dry environments, particles moved by wind, wears down land

oceanic water and wind - coastal processes

• lakes → wetland → squishy land → solid land

ice - glacial processes

• formation, potholes by freezing in concrete, all of Canada covered by glacial ice in last period - capable of doing a lot of work at certain times in history, glacial lake basin → don’t find a lot of stones (good for farmers) because lots of stones at bottom of lake

ex. Qu’appelle Valley:

• glacial drainage site!!! transported to oceans most likely, go through significant water places (Winnipeg, Hudson), at some point deposited

Tectonic Plates

mountains formed when Pangea came together, were huge! because of that force

• Himalayas - India thrust into underbelly of Asia (newer, so bigger!)

now mountains worn down because of exogenic processes

• western mountains older (Appalachian older than Rockies), so more time to be worn down

Different forces at different latitudes

Canadian/Brazilian Shields (very old rocks) core of the continents

• can be overlayed with other materials when thrust up from sea floor or deposition

demolition derby

• run into car, crush and move up, back up crash into something else, but like… driving across continents

Constructive and Destructive Plate Boundaries

destructive: crusts are consumed and forced into the depths

• volcanoes

• upon this boundary might be earthquakes (slip gradually or locked together then release suddenly)

constructive: tensional force, create new crust

• Compression: folds where crustal plates coming together, creating compressional force

• Tension: rearranging in plates

• both compression and tension creates changes in relief/elevation

  • will be a chance for things to move downslope (geomorphic processes)

Structural Landscapes

still reflects original structure

results of tensional force - when crust pulls apart crust, rearranges itself → relief! fresh! new! just created!

• process of creating relief

• as soon as relief created, landscape is going to be attacked by geomorphic processes (exogenic forces at the surface)

• volcanoes created because of these direct endogenic forces

These forces create relief:

• Germanic Relief

  • tensional

• Appalachian Relief

  • compression

Germanic and Appalachian Relief (Structural Landscapes)

these forces create relief

Germanic Relief: (tensional)

• forms of faulting

• lots of fault in south Germany

• Eastern Africa rift zone/valley system - will probably eventually separate from the rest of the continent; continent rift zone

Appalachian Relief: (compression)

• forms of folding

• old mountain chains in particular

• folding itself will create tensional forces at top of ridge (anticline), open up rock and more more erodible

Structurally Controlled Landsacpes

eroded structural landscapes, can kind of make out original features, but been extensively acted upon by erosion

based on faults: concentrated on anticlines, more worn down material; in synclines, harder to erode/more resistant by being pushed together

• what used to be high point is now low point, vice versa

Plunging folds: crosscut across surfaces, folding/compression created landscape, but then exogenic forces gives zigzags and dips to the structure

monoclinal: a tilting strata, passive role of crust, resistant framework, one angle

Germanic Relief (Structurally Controlled Landscapes)

geomorphic processes eroding a germanic structural landscape (like an upthrust block)

fans at break of relief

• river in confined space, then spread out as release of force

• dumps sediment load at the break of slope, confined flow converted to unconfined flow

Intruded Volcanism (Structurally Controlled Landscapes)

when not exposed, magma intruded into existing rock strata (weak spots), over fairly large areas, so not very visible at surface

land slowly erodes, magma underneath either slowly cools into large crystals, or is thrust into air/water and fast cools, turning to granite which is not easily erodible

once exposed, becomes large area of resistant rock

helps us trace existing resources, deposits of minerals, and determine distributions