Topography and Bathymetry of Earth m continent – ocean contrasts 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 m South Plate American s e d n A Central Andean Andes Plateau s e d n A Peru-Chile Plate subduction zone Nazca South Antarctic Plate AmericanAndes Pacific Plate Amazon drainage basin Amazon headwater basin: erosion Beni R. Lake Titicaca Amazon tributaries: transport Madeira R. 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 plate beneath s n i a t n u o M s h e c d western South American n e r A Subduction of Nazca T e l i ed crust Ch - u icken r e th e s i P R c fi i c a Subducted Nazca plate P t s a E 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 Eastern Cordillera c Landsat Themati La Paz Mapper Aug 2, 1987 Lake Titicaca Landsat Thematic Mapper Aug 2, 1987 Simplified section section Topographic swath profile 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 section 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 photo from Shuttle Arica Great western Escarpment Lake Titicaca Salar Uyuni La Paz d e Cuzco 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.