Geomorphic Processes:II. Exogenous II. Gradation Processes Weathering, Mass Wasting, Erosion, Transportationand Deposition

Geomorphic Processes:

Physical processes which create and modify landforms on the surface of the earth

Endogenous (Endogenic) vs.Exogenous (Exogenic) Processes

Rock Cycle

A. Endogenous Processes Endogenous Processes are large-scale landform building and transforming processes they create relief.

1. Igneous Processes

Volcanism: Volcanic eruptions VolcanoesPlutonism: Igneous intrusions

Tectonic Processes (Also called Diastrophism)

Folding: anticlines, synclines, mountainsFaulting: rift valleys, graben, escarpmentsLateral Faulting: strike-slip faults

Earthquakes evidence of present-day tectonic activity

B. Exogenous ProcessesAlso called Gradational Processes, they comprise degradation and aggradation they modify relief

a continuum of processes Weathering Mass Wasting Erosion Transportation Deposition

these processes are carried through by Geomorphic Agents: gravity, flowing water (rivers), moving ice (glaciers), waves and tides (oceans and lakes), wind,plants, organisms, animals and humans

1. Degradation Processes Also called Denudation Processesa. Weathering , b. Mass Wasting and c. Erosion and TransportationAggradation Processesa. Deposition fluvial, eolian, glacial, coastal

Relationship:WeatheringMass WastingErosionand Transportation

Together, these processes areresponsible forDenudationof Earths surface

WEATHERING

Weathering is disintegration and decomposition of rocks in situ no transportation involved produces regolith

More precisely, it involves the mechanical or physical disintegration and/or chemical decomposition that fragments rock masses into smaller components that amass on-site, before being moved by gravity or transported by other agents

The processes begin in microscopic spaces, cracks, joints, faults, fractures, lava vesicles and other rock cavities

Types of Weathering: 1) Physical or Mechanical Weathering, 2) Chemical Weathering, and 3) Biological Weathering

Physical or Mechanical Weathering Disintegration and decay of rocks via weather elements: high temperatures, extreme cold and freeze-thaw cycles No change in chemical composition of rocks Exfoliation due to thermal expansion/contraction and/or release of pressure when buried rocks are uplifted and exposede.g., Exfoliation Dome (Stone Mountain, GA) and Exfoliation Sheets (Sierra Nevada) Frost Wedging

Salt Wedging

Chemical Weathering decomposes rocks through a chemical change in its minerals

Oxidation important in iron-rich rocks reddish coloration like rust

Hydrolysis igneous rocks have much silica which readily combines with water

Carbonation and Solution carbon dioxide dissolved in water reacts with carbonate rocks to create a soluble product (calcium bicarbonate)

Biological Weathering plants and animals contribute to weathering.

Roots physically break or wedge rock

Lichens (algae and fungi living as single unit), remove minerals and weaken rock by releasing acids

Burrowing animals can increase weathering.Lichens

Talus Conesin the Canadian RockiesTalus pieces of rock at bottom of a rock fallLandslidesCan cause much destructionA msssive 300-ton boulder blocks a road in Southern California

La Conchita Landslide, January 10, 2005

Monterey Park Debris Flow, 1980

PCH near Pacific Palisades, November 1956

EROSION and TRANSPORTATION Various Geomorphic Agents, associated Processes, and resulting Erosional Features

Flowing Water Fluvial Morphology

Humid regions: Perennial streams and entrenched channels, rapids, waterfalls, plunge pools, potholes, meandering streams, bank erosion, oxbow lakes, etc.

Wind Eolian Landscapes deflation hollows, ventifacts, yardang, etc Tides and Waves Coastal Morphology Sea cliffs, sea caves, sea arches, sea stacks, wave-cut beaches, etc..

Moving Ice Glacial Morphology glacial troughs (U-shaped valleys), hanging valleys, glacial lakes,.

DEPOSITION Various geomorphic agents, associated processes and resulting Depositional Features

Fluvial Humid regions: Braided streams, sand bars, floodplains (alluvium deposits), natural levees, distributaries, deltas Arid regions: Alluvial fans, bajadas, piedmont alluvial plains, playas, playa lakes, Salinas (salt flats)

Eolian Sand dunes (Barchans, Parabolic, Transverse, Longitudinal, Star), and sand sheets

Coastal Sea beaches and coral reefs

Glacial Alpine: Glacial drifts, tills, moraines (lateral, medial, end, terminal, recessional, and ground) Continental: Till plains, outwash plains, drumlins, eskers, kames, erratic