lecture 3 -global geomorphology and tectonics Flashcards
define hypsometry
the measurement of land elevation relative to sea level
define bathymetry
the underwater equivalent to hypsometry / measurement of land elevation below sea level
earth’s hypsometry is bimodal due to…
thickness and density of crust
define isostasy
the state of equilibrium such that the earth’s lithosphere floats at an elevation determined by their thickness and density
what are the controls of elevation?
- creation of continental and oceanic crusts
- mountain range / continental collision (thickening)
- geomorphological processes cut valleys, sculpting individual mountains
define rifting
formation of fissures / breaks, through large scale faulting; moving apart
what is the Wilson cycle?
the cyclical opening and closing of ocean basins caused by movement of the earth’s plates
what is the supercontinent cycle?
aggregation and dispersal of earth’s continental crust
oceanic crust:
- young (200 ma)
- constantly recycled
- not complex
continental crust:
- recycled less
- modified and survive through deep time
what is a craton?
very old (3 billion years) stable parts of crust affected little by plate tectonics - continents form and reform around them
what is a shield?
an exposed craton
what is a platform?
craton covered by sedimentary rock
what is an orogen?
younger, mountain building parts of the crust
convergent margins produce…?
island arcs
continent - margin orogens
collisional orogens
what is a passive margin?
an ancient rift flank no longer tectonically active, uplift caused by flexure and erosion
topography reflects competition between the effects of which 2 energy sources?
internal (endogenic) and external (exogenic)
define endogenic
occur beneath the surface of the earth e.g. convection for plate tectonic movement
define denudation
processes that wear away the earth’s surface e.g. chemical and physical erosion
what is a nappe?
large body / sheet of rock that has been moved a distance of 2km or more from its original position by thrusting or folding
define shortening
the thickening of the crust achieved by faulting and folding
occurs in continent - continent collisions / convergent margins where no subduction occurs
what controls height?
- tectonics: rate of shortening, isostasy, topography
- denudation (lowering by erosion): influenced by slope, rock strength, climate
* the competition between tectonic vs surface processes
