Earth Surface Processes Lecture 2

Seite 1

Rain is causing erosion but there are other forces resisting it - vegetation. Big forested areas will yield far less sediment.

relief - highest point minus the lowest point at sea level

Strong linear relationship with relief - provides potential energy

How do macro scale processes affect the surface?

Tectonics, climate, erosion all affect surface topography and compete to yield the resultant topography. When mountains are uplifted, erosion responds and balances the uplift = steady state landscape where relief doesn't change. When erosion increases, the mountain range becomes lower - eventually a lowland

Biogeochemical interactions that weather out certain minerals

When 2 continents collide and both are buoyant neither one can sink below the other - thickening of crust and rocks are folded and deformed - massive uplift into a mountain belt

The thick crust protrudes with a deeper root floating on dense mantle

erosion causes uplift - exposes rocks that have been metamorphosed by high pressures in the mountain belts

Archimedes principle - boats...why do they float? Buoyant force is equal to the mass of the water displaced

Thickness and density of crust - determines how deeply it is sitting in to the denser fluid

Sea level and glaciers

glaciers retain a huge amount of water that would normally be involved in the hydrological cycle - causes a decrease in sea level - longer distance for river to get there. Once the glaciers melt they yield enough water to increase SL (eustatic)

Wood blocks representing thickness of continental crust

Erosion moving mass from uplifted surface at top and depositing sediment in the lowlands. Offloading of extra mass will allow the mountain belt to float up a little higher - isostatic uplift.

Glacier melts - lost mass from ice and loss from sediment mass and increase in sea level

Climate produces landscape responses that are not normal in space. Climate expresses selectively at specific locations

Precipitation falls as rain or snow depending on the elevation and the season. Mountains act as barriers to the atmospheric currents e.g. jet stream is deflected northward by the rockies

There are rain shadows and rainout zones and areas dominated by glaciers - influence the erosion response of landscape

Summer monsoon in india - warm moist air moves onshore as a southwestern monsoon.

Himalayas - annual pattern of rainfall tied to summer monsoon. Winter is dry. Snow falls in winter.

Climatic limits - why don't they keep growing if there is no rain to cause erosion? As they get uplifted they start interacting with climate so that snow falls - glaciers and snow start to erode. Ice control on relief and on more moderate, rainfall control.

Water on the earths surface as potential to erode sediment - spatial of erosion as well. Precipitation may be localised such that it impacts spatial patterns of erosion. Rainfall is higher in ridge crests than valley bottom. Drive the sediments through the ridges down to the bottom and out.

Positive and negative feedback

P - runaway process - it keeps growing and growing. Eg interest rate in a bank. More money so more interest

N - self regulating process - body temp goes up, start sweating, body goes back down to normal state - stable

Himalaya- highest monsoonal rainfall is at the mountain FRONT. Most of the rain is concentrated, a lot of relief = large amount of erosion down through the rivers and out to the sea. There is a thrust belt - movement along the fault - top and bottom parts moving in opposite directions. Highly metamorphosed rocks and other rocks brought to the surface. If we start eroding material then the uplift will increase - isostatic rebound to unloading of sediment mass. Net direction of movement of material will be along thrust fault toward the surfacee. Erosion causes more uplift which causes more erosion which causes more uplift unloading more and more sediment to the lowlands. Not a confirmed phenomenon.