# Whole Earth morphology Large scale topography. What are the largest topographic features of the Earth?

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Whole Earth morphology Large scale topography

What are the largest topographic features of the Earth?

Earth radius at equator > Earth radius at pole Earth radius at equator > Earth radius at pole –By 21 km (~12 mi) Why? Why? Oblateness? Results in a slow flow of mass towards the equator

Whole earth morphology versus

Size and rheology matter Size drives the internal pressure and the time it takes to cool down Size drives the internal pressure and the time it takes to cool down Rheology drives how “well” the inner material flows and moves Rheology drives how “well” the inner material flows and moves

High pressure Low pressure Eventually leads to hydrostatic equilibrium P1 = P2 = P3 => no pressure gradients

Is the surface of the earth smooth or rough? Why is there a bimodal distribution of elevation?

3.8 km 5 km 23 km 13 km The continents ride higher in the mantle due to lower density and greater thickness – isostatic balance Isostasy: Floating materials in a denser fluid

How thick a column of rock is needed to exert a pressure of 1 bar (or 10 5 Pa) at the Earth’s surface. How thick a column of water is needed? How thick a column of air, given its density is that of air at the Earth’s surface, 1.22 kg/m 3 ? How thick a column of rock is needed to exert a pressure of 1 bar (or 10 5 Pa) at the Earth’s surface. How thick a column of water is needed? How thick a column of air, given its density is that of air at the Earth’s surface, 1.22 kg/m 3 ?

Response of the mantle and crust to loading: Lake Bonneville http://geology.utah.gov/utahgeo/gsl/flash/lb_flash.htm http://geology.utah.gov/utahgeo/gsl/flash/lb_flash.htm http://geology.utah.gov/utahgeo/gsl/flash/lb_flash.htm

Calculate the expected deflection of the lithosphere beneath a thick icesheet. Say the icesheet is 4000 m thick, and ice has a density of 917 kg/m3. (The Antarctican icesheet is roughly this thick at its maximum thickness.) The thickness of the crust (of density 2700 kg/m3) beneath the center of the icesheet and the region outside of it is the same. The density of the upper mantle that gooshes out of the way to allow this deflection of the surface is 3300 kg/m3. What I want to know is how far down the rock is depressed beneath the load of the ice.

Rock Cycle Repeated creation and destruction of crustal material (rocks and minerals) Repeated creation and destruction of crustal material (rocks and minerals) Volcanoes, folding faulting, uplift Volcanoes, folding faulting, uplift –bring rock, water, gas to the Earth surface Rocks disintegrates Rocks disintegrates –weathers by exposure to water and air Transport by gravity, water, wind Transport by gravity, water, wind –weathering products go back to the ocean Deposition and burial Deposition and burial –formation of sedimentary rocks Deep burial Deep burial –metamorphic rocks Uplift, intrusion, or extrusion Uplift, intrusion, or extrusion –rocks exposed, process begins again Weathering, transport, deposition

Landform creation by: Weathering, transport, deposition Weathering agents move into soil and rock along a weathering front Weathering agents move into soil and rock along a weathering front –brings fresh rock up Weathered material (regolith; soil) on surface + material brought in by wind, water, ice, animals = weathered mantle Weathered material (regolith; soil) on surface + material brought in by wind, water, ice, animals = weathered mantle Mantle remains in place or moves downslope by gravity Mantle remains in place or moves downslope by gravity –water can also carry it downslope –wind can remove it

Brook manual, p. 2-4 Q 2-3 Q 2-3 –Magnetic declination: the difference between geographic north and magnetic north –Magnetic declination of Philipp quad= 7.5 deg E 7.5 deg E –Verbal scale in in/mi Philipp: 1” = 62,500” =.98mi Philipp: 1” = 62,500” =.98mi Kingston: 1” = 24,500” =.38mi Kingston: 1” = 24,500” =.38mi –Verbal scale in cm/km Philipp: 1 cm =.625km Philipp: 1 cm =.625km Kingston: 1cm =.24 km Kingston: 1cm =.24 km

Brook manual, p. 2-10 Q 2.6 Q 2.6 –Horiz scale is 1:25,000 or 1” on map = 25,000” on ground 1:25,000 or 1” on map = 25,000” on ground –Vert scale is 1” = 100’ or 1”=1200” 1” = 100’ or 1”=1200” –VE=Horiz scale/Vert scale = 25,000/1200=20.8 25,000/1200=20.8 Q 2.7 Q 2.7 –Average gradient (or slope) = rise/run, in words –500 ft/(520 yds x 3 ft/yd)=500 ft/1560 ft = 1 ft/3.12 –for every vert. ft of elev gain, the dist moved in 3.12ft

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