Topography and Bathymetry of Earth
Continents: very complex crustal m deformations and mantle interactions Sub-ocean: entirely created since 200 Ma by seafloor spreading Continental mountain ranges and plateaus developed by Cenozoic diffuse plate boundary processes
m Continental mountain ranges and plateaus developed by Cenozoic diffuse plate boundary processes
m continent – ocean contrasts
Erosion and lateral transport m of rock dominant Sedimentation dominant water, water everywhere…. The three end-member climatic- geomorphic regimes determined by the role of water
Frozen water: glaciers & ice sheets Liquid water: groundwater/fluvial networks
Very little water: deserts Fluvial and glacial-fluvial networks:
- The primary engines of erosion and transport of rock
- The pervasive and outstanding terrestrial landform Flux of rock mass: three basic components of a large fluvial basin
A. Up stream net loss: erosion
B. Down stream transport: no net loss or gain
C. End stream net gain: deposition South American s e d Andes n A
A n Peru-Chile d m e C South Pacific Plate s subduction zone e n American t r P a Plate la l Nazca Plate t A e n a u d e a n
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Antarctic Plate Amazon drainage basin Amazon headwater basin: erosion
Beni R.
Lake Titicaca Amazon tributaries: transport
R. ira de Ma Amazon River: transport Amazon delta: deposition Amazon drainage basin
Beni Basin Elevation, meters Elevation, meters
Beni R. basin South American Plate
Nazca Plate 8 cm/yr Subduction of Nazca plate beneath western South America
s n e i is ta R h n c c u ifi n o c re M a T s P e t ile d as n E -Ch A u er P thickened crust S u b d u ct ed N az ca p la te Altiplano cross-section
South America Plate
Shown schematically in next slide Two phase model for Altiplano development
West East
monoclinal structure
major fold-thrust system on the eastern flanks of the Andes The subduction zone and subducted plate are on this side, but are not shown.
Focused, high erosion on one side may produce a highly asymmetric tectonic response
Steep regional slope and high precipitation produce very high erosion rates: 1-5 mm/yr Precipitation orographically enhanced precipitation Orographic snow & ice concentration of precipitation produces very high erosion rain rates
• rainfall at lower elevations •snow at higher elevations •glaciers and icefields at highest elevations Eastern side of Peru Lake Andean plateau Photo from Titicaca Shuttle
Bolivia
Chile North Photo from Shuttle Landsat Thematic Photo taken Mapper Image Shuttle Landsat Thematic Mapper Aug 2, 1987
E a s te rn C o rd il le ra
Lake Titicaca
La Paz Landsat Thematic Mapper Aug 2, 1987
Simplified Topographic swath profile section
n o ti sec Beni drainage basin V-shaped valleys, landsliding hillslopes, rivers incising bedrock Central Range, Taiwan
The Central Cross-Island Highway travels up the Liwu Chi, through Taroko gorge. The gorge has formed where the Liwu Chi cuts through competent marbles and gneisses. Bright, clean rock surface indicates the water depth during passage of typhoon Herb (1996). Car for scale. Central Range, Taiwan
Large landslide in the headwaters of the Liwu Chi. Such high-magnitude, low-frequency landslides dominate the sediment supply to the rivers draining the Taiwan mountains. Removal of landslide debris is accomplished mainly by major storms Back to Bolivia
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Tectonics vrs erosion: end member cases Stress limited uplift
crustal thickeness and average elevation Tectonic Crust limited by balance between horizontal inflow and vertical stresses Arid climate: transport limited, low erosion rates “steady state” mountain belt: tectonic inflow = erosional outflow w erosi outflo onal onal outfl erosi ow
Tectonic Crust Crustal thickness and average inflow elevation limited by erosion rate Wet climate: weathering limited, high erosion rates Mountain belt “erosion machines”
Alps SE Alaska- BC Taiwan Central Range (5-10) Himalayas New Northern (2-7) Guinea Andes Highlands Eastern Andes (1-5)
erosion rate New Patagonian mm/yr Zealand Andes Southern Alps (5-10)
Precipitation-relief index of erosion, computed as product of mean annual precipitation in millimeters/year and relief within ~100 km2 windows in meters. Values range from zero (blue) to about 13500, with values above 2000 in red. glacial dominant erosional process glacio-fluvial fluvial
Alps SE Alaska- Himalayas BC Taiwan Central Range New Northern Guinea Andes Highlands Eastern Andes
Patagonian New Andes Zealand Southern Alps Precipitation-relief index of erosion, computed as product of mean annual precipitation in millimeters/year and relief within ~100 km2 windows in meters. Values range from zero (blue) to about 13500, with values above 2000 in red. photo from Shuttle Lake photo from Titicaca
Shuttle La Paz
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Salar de Uyuni Cross-sectional view across Northern Chile-Bolivia
Great WSouthestern America Plate Eastern Sub-andean Escarpment Altiplano Cordillera f o reland fold- thrust belt Stable, undeformed crust flexure of upper crust plateau uplift
upper crust
Shortened and thickened ductile lower crust Mantle “top-down” erosional system
major Atacama atmospheric hyperarid moisture desert fluxes
Drainage systems driven by orographic precip: “side-cutting” erosional system westerlies “top-down” erosional “top-down” erosional system system
Canyon systems
Atacama hyperarid desert
Drainage systems driven by orographic precip: “side-cutting” erosional system Southern Peru
incised stream profile
Northern Chile
groundwater
Atacama
groundwater GroundwaterGroundwater sappingsapping networksnetworks
River networks formed by subsurface flow piercing the surface and undermining overlying material.
3-D Perspectiv e view
ASTER 321
Amphitheater headwalls Amphitheater headwalls