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Surface Final
final exam
| Question | Answer |
|---|---|
| Sedimentation formula | mass/(time x length) |
| Density formula | p = mass/volume |
| Mass formula | volume x density |
| Flux formula | Mass/time/distance |
| Getting from mass/time to length/time (erosion rate) | • M/tA = mass/time x length^2 • But we want a volume not a mass • M/p t A = mass x L^3/time x L^2 X mass o Mass and Length cancel out o Left with L/T |
| Density of sediment | 1500 kg/m^3 |
| Surface processes | the action when a force induces a change, either physical or chemical, in materials on the earth’s surface |
| Force formula | mass x acceleration • Mass = kg (usually) • Acceleration = (mass/time^2) meters/sec^2 |
| Energy formula | force x distance = (mass x acceleration) x distance • Measured in Joules • Think about rate at which energy is expended. Drives how fast processes happen |
| Power formula | energy expended/time • Units are Watts |
| Pressure formula | Force/Area • Or stress, more generally speaking • Units are Newtons • Force is F = m a |
| Hypsometry | line tells us about the amount (percentage) of earth surface above or below that point |
| Histogram | distribution plot tells us about how much of the earth’s area is in a certain range of depths/elevations |
| Relative to sea level, crustal elevations | • average elevation of continents – 0.8 km above sea level • average depths of ocean – 3.8 km |
| Crustal thicknesses | o Oceanic – 10km o Continental – 40km |
| Pressure of soap on water column | o Density x (LWT) gravity/LW o Pressure = density of water x T x acceleration due to gravity • Pa = pw Ta g o So distance between bottom of soap & thickness of soap = T • Pb = pw Tb g + ps Ts g o At equilibrium (no motion) Pa = Pb |
| How to find pressure of continental lithosphere? | • Pcl = pcl Tcl g + pa Tacl g o Density of continental lithosphere o Thickness of continental lithosphere o Gravity o Density of asthenosphere o Thickness of asthenosphere beneath continental lithosphere o Gravity |
| How to find Pressure of oceanic lithosphere? | • Pol = pw To g + pol Tol g + pa Taol g o Density of water o Thickness of ocean o Gravity o Density of ol o Thickness of oceanic lithosphere o Gravity o Density of asthenosphere o Thickness of asthenosphere beneath oceanic lithosphere o Gravity |
| At isostatic equilibrium density is...? | Pcl = Pol |
| Difference in crustal elevation formula | (Tacl + Tcl) – (Taol + Tol) |
| depth of compensation | line of equal pressure across the bottom when we draw crustal thickness models |
| Isostatic response to changing crustal thickness formula | (Tc + Tm) before (Tc + change in Tc) + (Tm + change in Tm) after |
| Isostatic response pressure formula | Pressure after = pcl Tcl g + pcl (chance in cl) g + pa Tacl g + pa (change in Tacl) g |
| What how would pressure change with 10 km of erosion? | after cancelling it’s 0 = pcl (change in Tcl) + pa (change in Tacl) So –pcl(change in Tcl) = pa (change in Tacl) Then (change in Tacl) = -pcl /pa (change in Tcl) And (-10 km) = -pcl/pa (change in Tcl) |
| Change in Tacl during isostatic disequilibrium | -pcl/pacl • pcl = 2800 kg/m^3 • pacl = 3300 kg/m^3 -2800 kg/m^3/3300 kg/m^3 = -0.85 • the asthenosphere is will go up 0.85 times (85%) more than the continental lithosphere is going down -10 km of erosion → 1.5 km of going down |
| Methods for changing thickness? | • glaciers • sediment • mountain building • adding water |
| Flexural compensation | when a heavy load is placed on a non-rigid surface, the surface may bend to compensate the load (rock on a ruler or hawaii) |
| When water hits the earth surface, where does it go? | Infiltration, evaporation, or overland flow |
| Hortonian Overland Flow | overland flow when the precipitation rate > the infiltration rate |
| Subsurface storm flow | through biogenic passages, faults in the rock (cm/min-hr) |
| Saturated overland flow | Rain falls on a saturated surface. So it flows across |
| Groundwater flow | can move through pore spaces above the water table It goes down to the water table, where all the pore spaces are full (saturated zone). Moves as groundwater (could eventually go into water table or come out at the bottom of the slope) cm/hr-day |
| Antecedent moisture | Seasonal control on how much flow we have and where |
| How is material moved in the badlands? | Wind when it’s dry. Water flowing with gravity (overland flow). Mass wasting (landslides). A water droplet kicks up sediment (rainsplash) |
| Centimeter scale topography | • incisive process – water in little valleys, as they pick stuff up and move them, they get deeper. • Mass wasting takes it from high to low, brings little peaks down into the valleys, fills them in • Rain scatters sed, flattens out small scale topo |
| Channel initiation theory 1 - channels begin where overland flow dominated over diffusive processes | o more overland flow than things like rainsplash o process threshold (where incisive processes win out against diffusive) |
| precipitation volume/time formula | Volume/time = (depth/time) x area |
| Simplified formula for discharge | mean velocity x width of channel x depth of channel |
| Shear stress formula | T = p g H sintheta |
| Critical shear stress graph | o Critical shear stress to start moving sediment on x o Grain diameter on y axis o CSS increases as GD increases o Log-log axis - power functions o Nonlinear equation (nonlinear increase in shear stress) |
| Channel initiation theory 2 - channels begin where flow initiates sediment motion | o Tcrit < pg (Hsinthea)crit • Hsintheta crit is the minimum combination of depth and slope to move the material |
| Channel initiation theory 3 - channels begin when small-scale landsliding occurs in hollows | • happens where there’s logging • the soil comes off and there’s just bedrock |
| Channel initiation theory 4 - groundwater sapping | • formed by groundwater movement – concentrated in valley floor |
| drainage basin | region contributing flow to a point |
| drainage or source area | area of region contributing flow |
| drainage density | total length of channels/drainage basin area |
| length of channel maintenance | inverse of drainage density (how far is it from one channel to the next?) |
| Important points in a drainage map | -basin surrounded by the drainage divide -the lowest point is the basin outlet |
| What controls drainage density? | area/slope relationship |
| Strahler? | stream order numbering |
| Practical formula for discharge | Q = cross sectional area x mean velocity |
| Reynold's number formula | • Re = p v L/ M o p = density of fluid o v = velocity of fluid o L = length scale o M = viscosity of fluid • When Re <500, you get laminar flow • When you get >2000, you get turbulent |
| Velocity in a channel formula | v = v*/K ln H/H0 • H – height above the bed • V – velocity • K – constant • V* - shear velocity = sqrt)shear stress/density • H0 – bed roughness |
| Shear stress | viscosity * change in velocity/change in height |
| Where does "lost" energy in a stream go | • Kinetic (water is speeding up) • Kinetic to move sediment • Loses some through evaporation (latent heat energy leaving) • Loss due to friction (heats water up) • PE converted to sound • Breaking chemical bonds in material it’s flowing across |
| Formula for loss of PE rate | • mass x gravity x height • or • density (l*w*h) g deltay |
| Erosion rate equation | mass*volume / time*surface area*mass = L/time |
| Density of quartz | 2660 kg/mm^3 |
| Density of water | 1000 kg/mm^3 |
| Density of sediment | 1500 kg/mm^3 |
| volume formula | mass/density = l*w*h = A*h |
| Difference in elevation (isostacy) | (Tacl + Tcl) - (Taol + Tol) |
| Pcl = ? | pcl * Tcl * g + pa * Tacl * g |
| Pol = ? | pw * To * g + pol * Tol * g + pa * Taol * g |
| change in Tacl = ? (isostatic uplift) | -pcl/pm * change in Tcl |
| change in Tcl = ? (total erosion) | change in E/(1-pcl/pm) |
| By what degree of magnitude does tensile strength vary? | 6 orders of magnitude (quartzite is a million times more difficult to erode than weathered sandstone) |
| Why, as sediment mass increases, does erosion rate increase and then decrease? | as it increases, more grains are eroding at the same speed so there's more Kinetic Energy. when it decreases, there are too many grains hitting each other, and cushioning the bed |
| How to use a shields diagram | -calculate RE -go up to the threshold curve & over to 7 -set sheilds = to that value -only thing you don’t know is the critical shear stress, which you can solve for -then you see whether or not the stress you have is the stress you need |
| Shear velocity | Sqrt)shear stress/density of fluid = squrt)Tb/pf = pgHsintheta |
| Find Re for shields | (densityfluid*shearvelocity*graindiameter)/viscosityfluid |
| Shields number | critical shear stress needed to entrain grain/(pg-pf)g*diamter |
| Flexural compensation equation | size of load/2pi * {g(pm-pc)/D}^1/4 |
| Types of rigidity | Fully rigid (no bend), Fully Airy Isostacy (all the bend), Flexure (mixture) |
| Why, as sediment size increases, does the threshold of entrainment curve decrease and then increase? In the Hjulstrom diagram. | The smallest grain sizes are in the laminar sublayer and some clay-size grains are flocculated. After ~0.1 mm they enter into the turbulent flow regime |
| In a graph of slope (x) vs watershed surface area (y) where there is a negative linear relationship for channel initiation threshold, where will you be standing in a channel vs not? | under the line, <Fcrit, not in a channel. over the line, >Fcrit, in the channel. |
| Montgomery and Dietrich summary | They discuss the point which separates a smooth hillslope from an incised channel and why it forms where it does. They measured channel area and slope angle. |
| Molnar and England summary | The authors are referring to whether tectonic uplift led to change in climate, or whether climate change lead to the appearance of uplift. They looked at evidence from geomorphic, paleobio, see, to argue that late Cz climate change was responsible |
| Why does the badlands have channels but the valley floor doesn't? | valley is flat, badlands have relief. Valley has more vegetation to hold material in place, badlands doesn't. they both have different materials, grain sizes, etc. |
| Stream power equation | w = p Q g sin theta/width |
| Forces that keep grains in place vs forces that move them | -what’s keeping it in place? • Gravitational force • Friction -what might move it? • Small amount of buoyancy • Inertial forces • Eddies on the backside create a drag force • Lift force through differential pressure |
| Sediment transport | -relative velocity is the important aspect of drag. It’s moving in the direction of the current. -the v of the fluid is high above the grain, low below it. So there’s high pressure below the grain and low pressure above. Hair dryer and ball in a beaker |
| What are the problems with the Hjulstrom diagram? | all grains were spherical quartz, all flow depths were 1 m. |
| Settling velocity | • When Fg=Fd, no acceleration (terminal velocity) o We’ll think of it as settling velocity, or w o There has to be some downward velocity o Grain is positive settling velocity, counteracting force due to gravity |
| Force due to gravity vs force due to drag | o Fg = (pg-pf) g pid^3/6 • 6 is the diameter o Fd = ½ pf Cd (pid^2/4) v^2 • Cd is drag coefficient • 4 is cross sectional area |
| Settling velocity formula | Squrt)4/3 g (D(pg-pf))/pf Cd o g is gravity o Cd is drag force o D is diameter o pg is grain density o pf is fluid density |
| Drag coefficient & stokes diagram | -log graph -stokes region where it’s easy to predict drag coefficient. It’s pretty much just 24/ reynold’s number -drag crisis where it suddenly drops |
| Fluvial form | -channel types – bedrock, alluvial, and mixed -end members – rock floor & alluvial -rock floor – mostly bedrock, not much sediment -alluvial – wholly made up of sediment. No rock at the surface |
| Why are bedrock eroding rivers important? | -primary non-glacial erosion mechanism -communicate base level changes -control basin response time -set the lower boundary conditions for hillslopes |
| Primary mechanisms for erosion of bedrock-floored channels | Abrasion – have to have moving suspended sediment Cavatation – high velocities, causing water to move below vapor pressure Plucking – jointing to break off and move |
| Abrasional forms | -potholes • fractures are important in initiating things like a pothole • less hard rocks -fluting and polish • flow from top to bottom. Flutes migrating up. • Hard rocks |
| Controls on abrasion | -measured rock tensile strength • quartzite highest, weathered ss lowest -sediment abundance • as it increases there are more grains and more KE o tools effect • at a certain point the sediment hits only sediment not KE o cover effect |
| Cavatation index equation | p-pv/½pv^2 Less than 3 = cav likely most likely as water pressure approaches vapor pressure |
| Types of alluvial channels | -straight -braided • multiple intertwined channels -meandering • single channel |
| Sinuosity | -measure of the curvy-ness, (distance along the channel/valley distance (straight across)) -perfectly straight = 1 -accounts for wavelength, amplitude (up & down from middle) |
| thalweg | path that traces the deepest part of the channel |
| pool | relatively deep section of river (troughs and crests of thalweg). Can be lower velocity. erosion at bottom. |
| riffle | relatively straight, shallow section of river |
| Bar | opposite to cut bank? |
| Controls on alluvial stream type | specific stream power, median grain size. (braided, highest for both) Also what the dominant load type is |
| Flume experiment for alluvial channels | -flow distance gets longer as it starts to meander -the distance is getting longer, but the elevation is the same as either end. Reduces the slope. |
| Base level | -the ultimate lower elevation limit to erosion (sea level for us rn) |
| local base level | • if you have a place with an extremely hard rock, the river might not be able to erode it • a lake might act as a local base level – can’t erode beneath the lake surface |
| base level changes | • Changing eustatic sea level • Change in relative base level if the continents go up or down |
| How does sediment get into & out of an area? | -in – bedload, suspended load, dissolved load from upstream, runoff, mass wasting, wind -out – carried out by river (bedload, suspended load, dissolved load) |
| Graded stream | every reach is in equilibrium. each stretch of the stream is the local base level for whatever section is just above it. |
| Moving from high to low elevation | -Q increases (bc drainage area increases) -sediment load more, you get more tributaries coming together -sediment size? smaller -at top high shear stress. Don’t have lots of water, so need high slope. -smaller grains, don’t need as big shear stress. |
| Knickpoints | steeper than the area downstream or upstream of them |
| parallel retreat (Niagara falls) | • erode weaker stuff underneath harder stuff until harder stuff collapses. Moves in the upstream direction |
| slope replacement | • very steep slope • water is eroding the steep part (perpendicular) faster than the surface of the land is eroding downward • steep part moves up profile • change in base level causes it • communicates a change in base level. Like a slinky |
| differential rock strength | • hard rock made up for by the slope • doesn’t move upstream. Knickpoint is stuck, not migrating |
| Localized uplift | • or you cold get a fixed knickpoint from not making the rock harder, but making the ground higher • also responds with elevation compensation • now it has to erode more rapidly where uplift is taking place |
| scaling relationship between radius of curvature and meander length | • radius/width ratio is ~2-3 • if it’s too wide, there’s less force delivered to the cut bank? o Or. Like. It gets too floopy and pinches itself off. |
| Why do streams meander? | -^ slope → ^sinuosity -stream power is PE converted to KE. Also influenced by slope -excess energy from more slope, it becomes spread out along the channel -meander is like running, straight is like walking. More energy in the same area |
| graph with discharge x, and frequency, magnitude, and work on y. | • so frequency (discharge) is negative linear, magnitude (sediment load) is positive linear, and total work is an inverted parabola. most work done at bankfull stage, which determines width. |
| What do terraces tell us? | • Tells you the position of a river at a previous time. Abandoned floodplains. • Mostly old river sediment. You can date old terraces and figure out timing of abandonment |
| Depositional terraces | o Nepali river is bedrock on bottom, alluvium on top. If it filled up and aggraded, it was depositional. o Terrace tread – top surface of depositional terrace (old gravel, stream material) o Abandoning an alluvial surface |
| Erosional terraces | o Strath – top of erosional terrace where bedrock has been cut o Just kind of cut across o Abandoning a bedrock surface o Diagram explains it better. • Cut infill – cutting into your own terrace as you go down |
| paired vs unpaired fluvial terraces | • Paired is more symmetrical (river has gone straight down) • Paired is parallel to the current stream • pairing suggests system-wide changes • Unpaired is more zig zag • may be simply scraps left behind as river downcuts |
| Terrace creation drivers | o climate o uplift o humans o base level changes |
| Why do streams meander again? | If you increase the energy, you need to dissipate it somehow, and streams do it by sinuosity. Increasing energy can happen through slope increase. |
| terraces and stable knickpoints (not moving) | • a profile for a previous river would be just moved to the NW of the current profile, mirrored basically. The knickpoints are the same places. |
| terraces and migratory knickpoints | ??? |
| relative dating | o superposition o cross cutting (igneous intrusions & valley incision) o inclusions |
| numerical dating | o cosmogenic radionuclides – produced when high energy cosmic (not solar) rays enter the earth’s atmosphere at .5 speed of light, and cause transformation |
| cosmogenic nuclides | o 10^18 of these on the earth every second. Small enough that they can pass through most things, but sometimes an atom is in the way and they’ll collide. o Run into atoms, kick off some stuff, the stuff goes and messes with other atoms. |
| C14 dating | abundance of C14 & C12 (ratio) in plants is approximately equal to the amounts of C14 & C12 in the atmosphere. Once it dies, the C14 will starts to decay, whereas the C12 is stable. Assuming 14C is well mixed. |
| Limitations of C14 | • need organic mater • and it’s a really short half life • measurement instrument. So if it’s like +- 5 atoms. But the error increases as you move out, to the point that it is the same as the age you get. 5,000 yrs is probably the limit . |
| nuclide production vs decay | • Initially the N is zero, so there’s only production. The amount over time will increase linearly with the slope being P • Over time, there will also be decay. So eventually it will flatten out a little bit assumes constant production & steady erosion |
| Erosion & cosmogenic radionuclides | if it’s eroding, you’ll get more over time. And you get more CRNs if it’s a slow erosion, than a fast erosion. |
| migratory knickpoint types | • Slope replacement (change in base level) o Migratory o Higher erosion rate than upstream or downstream • Parallel retreat o Small dip on a hard rock o Higher erosion rate than up or downstream o Migratory |
| Localized uplift | (small section of the channel going up faster than the rest) o Had a much higher erosion rate than upstream or downstream o Focused on particular location - fixed |
| differential rock strength | o See if geology is homogenous, or if knickpoint is associated with a stronger rock o Steeply dipping lithology with harder rock in middle (along the steep bit in a longitudinal profile) o Similar erosion rate across types o Fixed |
| Knickpoint migration evidence in channel profiles | -there could be terraces downstream, erosional -terrace would come off the lip of the knickpoint -the stream is the local base level for the tributaries. So as the knickpoint passes upstream, it passes the tributaries, & each has its own knickpoint. |
| Hack’s Law | • deltaz/deltax = -k/x o x is distance downstream o z is elevation at that distance o k is constant – steepness index • influenced by: sediment size & load rock type & strength stream erosion rate |
| Movement of materials on a hillslope | -gravity…generally -creep -overland flow -rainsplash -wind -bioturbation -fluvial processes in channels -landslide -heave by clay expansion |
| Hillslope processes: mass wasting | -creep & heave processes -slope stability and the factor of safety -landslides & landslide topography -debris flows and debris flow deposits |
| types of creep | -continuous creep processes • slowly but continuously • almost exclusively by gravity -episodic creep processes • every once in awhile, but still slow |
| biogeomorphic creep | • tree throw (episodic) • animal burrowing (episodic) • worms doing their thing |
| Rainsplash creep | • episodic. High KE. Then velocity goes to 0, and the energy is transferred to the soil • if it’s horizontal the grains are being displaced equally in all directions. If it’s on a slope, more is transported downslope. So flux depends on slope. |
| Hillslope creep flux equation | Q → mass/width of hillslope * time |
| Heave by ice lensing part 1 | • somehow water is drawn to the freezing front underground • ice is expanding and pushing the surface up • you can do this with shrink and swell clays as well • goes the direction of least resistance, perp to surface |
| Heave by ice lensing part 2 | o non-uniform heave among particles: most at top, least at bottom • when the heave is relaxed, particles go perp to gravity. So they move slightly in a downslope direction o ones that were at the top got heaved up more, and fell further downslope. |
| Heave by ice lensing part 3 | • No net movement when the slope is 0. So also a dependence on slope. • Evidence would be bent trees. The base of them goes downslope so they rotate. But then they bend because they like to grow straight up because sun. |
| Hillslope material removal equation | -delta v/delta t = -1/p (qout-qin) delta y • v is volume • t is time • p is density • q is flux • y is width -or -1/p delta q delta y |
| Flux off of a hillslope...more? | q = -k dz/dx • k is a constant, related to the process/material • so you take data points, graph em on q vs slope graph, slope of line is k |
| Diffusion equation | dz/dt = k/p d(dz/dx)/dx • ^diffusion equation. we can group k/p and make it into a large K and that’s the diffusivity • dz/dx is slope which is constant. If negative, means its going down. |
| Curvature & diffusivity | K = diffusivity and (d(dz/dx)/dx) = curvature If dz/dt is constant everywhere, then curvature is the same everywhere |
| Epiorogenic | flexural elevation changes in the absence of tectonics. |
| flux equation | -k (dz/dx) |
| erosion equation | • dz/dt = K (d(dz/dx)/dx) o diffusivity (big K) is k/density o the rest is curvature |
| Landslides on larger, vegetated slopes | -like the Japanese video. Moving down a relatively straight surface. Many of the trees stay upright. Translational landslide. -also in the blue hills badlands translational landslides |
| normal stress equation | pgh costheta costheta |
| shear stress equation | pgh costheta sintheta |
| shear strength equation | C + normal stress * tangent of angle of internal friction cohesion + effective normal stress (tangent of angle of internal friction) |
| bulk density equation | psaturated w + pdry (H – w) all / H • H is height of the whole package • Higher w higher bulk density |
| water pressure equation | • P = pwgW • Water helps support some weight of the overlying material o Like water supports some of your weight in the pool • Reduces normal stress |
| effective normal stress equation | normal stress – water pressure |
| factor of safety equation | shear strength/shear stress • C + (bulkdensitygH costheta costheta – water density g w) tan angle of internal friction • / • bulkdensity g H costheta sintheta -would be 1 when the hillslope is failing -greater than 1 if it’s stable |
| How do you take a stable hillslope & make it unstable? | -lower shear strength • lower cohesion (deforestation) • increase water table (dams, rain, snowmelt, etc) • lower angle of internal friction (weathering, earthquakes) -increase the shear stress • increase the slope |
| Translational regolith sides | -moves across a planar surface -regolith – loose material on top of bedrock -uplift is very fast, so erosion is very high |
| Translational rock slides | -you have a rock with a planar surface at an angle -can happen on a large scale as well (1km of rock in indus river valley) |
| Rotational slides | -curved failure plane. Like more of a bowl than a board. -has scarps at top, minor scarps at middle, rumply thrust faults at bottom (foot). landslides can move quickly on a cushion of air curved failure plains typically in unconsolidated material |
| How to identify past slides | -head scarp, where material pulled away -rumpled surface (small grabens and generally hummocky topography) -toe -ponded drainage (cut off past river) |
| Debris flows | -collection of colluvium in hollows, then water happens. Hollows typically high in landscape. Move like a fluid. -tend to coalesce from small flows in first-order drainages -can move as much as 10m/s -tend to be quite dense (2000kg/m^3) |
| normal stress in a debris flow | (ps – pf) Vs g H costheta - Pw • ps density of solid • pf density of fluid • Vs is fraction of debris flow that is solid • H thickness |
| shear stress in debris flow | y is how high are you above the bed (parallel to surface across which it is moving). Max shear stress at bed, 0 at top of flow. -shear stress(y) = pg(H-y) sintheta |
| Yield stress (needed for flow to occur) | T = pg (H-y) sintheta • H is like height above the ground, from the floor to the top of the flow. It’s up & down. • y is the height from somewhere on the ground to somewhere within the debris flow. It’s parallel to the ground |
| Bingham fluid | acted on by small shear stress, they behave like a soild. High shear stresses, behave like a fluid |
| debris flow levees | sometimes the debris flow goes out of the channel a little and stops moving because what spills out it the top (solid) part of the flow |
| Meuselli effect/kinetic sieving | -shaking the golf ball to the top. Big stuff jumps, small stuff fills, big doesn't have space to go back down. Reason for coarsening upward sequence/big stuff at top/front of flow. |
| Debris flow fans | Flowy looking topo at surface, variety in grain sizes. In death valley, oxidation can show how old it is. Fans typically composed of different events. Matrix supported. Diamicton High topo, colluvium accumulates, episodic weather events generate slides |
| Weathering | physical, chemical, and biological alteration of rocks and minerals, as they come in contact with fluids and stresses at the Earth surface. Happens in-situ. No movement. |
| Physical weathering | -breaking of chemical bonds that hold rocks together. • Exfoliation • Frost shattering • Root intrusion |
| Chemical weathering | Chemical bond breakage • dissolution pits |
| Weathering vs erosion limiting | -rock trolls picture is weathering-limited. So it is transported faster than it weathers. Weathering < transport. -transport limited landscape, weathering > transport |
| Cross section of weathering | -top is mobile regolith (stuff broken down enough to be moved) -under that is saprolites -then saprolite & other stuff is weathered bedrock -regolith is everything from the surface to the bedrock I guess |
| Incongruent weathering reactions | something is leftover when it’s over • secondary minerals (things like clays, oxides) • mineral resistance o increases stability down the bowens (or goldwich) |
| Congruent weathering reactions | everything is removed • leftover, ions dissolved in the water • some ions are more likely to stick around. Ionic potential (valence/ionic radius) tells the charge density, likelihood to react. |
| Reaction rate equation? | k – Ae^(-Ea/RT) • Ea is activation energy |
| Water & CO2 as regulators | -how much water is there, how long does it have to react -increased water & temp → increased weathering • driven by global circulation patterns CO2 -mixes with water to create carbonic acid -also from plant decay and respiration in regolith |
| oxidation | • loss of electrons by an atom to another atom, often oxygen, changing its charge state by +1 |
| Hydrolysis | -aggressive hydrogen ion substitution for cations in minerals -important because it uses feldspars and theyre everywhere |
| Carbonation | -simple solubility & hydrolysis (congruent) -dissolution (creates carbonic acid) • colder water, can dissolve more CO2 |
| Catchment chemical fluxes | need to know discharge, watershed area, amount of material at discharge point. You can take the amount/area you can multiply the discharge. It gives you a rate. Divide rate by area. |
| Exfoliation | -how deep were the rocks previously buried? • metamorphic? could be 30km & billions of N of pressure -how much compression is there? • compression at great depths, and they expand as they’re exhumed • Rocks fracture, causes exfoliation joints |
| Thermal expansion | -heating exterior, cool interior – tensile stresses (spallation) -cooling exterior, hot interior – compressive stresses -differential expansion (quartz will expand like 3x as much as feldspars) -potatoes and rocks both transfer heat by conduction |
| Spallation rates | This makes chunks fall off. o the falling off is an erosion process o the spallation is a weathering process • to get the rate you multiply the %surface covered by the average chunk size (per event) • then you need events/time period |
| Heat flux? | -q = -k (dT/dx) -dT/dt = K (d(dT/dx))/dx |
| Physical weathering - water & ice | -water expands 10% when it freezes (but can go up to 13%) -water and ice can exist at the same time in the rock -cracks & pores contain water -water migrates from high to low energy state, could make pressure high enough to break rock |
| Frost shattering | • max growth rates are 1cm/day • crack growth most rapid when o temps are -5 to -15 o permeability of the rock is relatively high o –water availability is relatively high |
| root intrusion | -mandrakes? -root depth & mean diameter are controls |
| Wetting & drying | -mudstones -clays can be shrink-swell -erosion rates might be higher on banks than in river beds because of this • creation of strath terraces commonly with clay-bearing lithologies |
| Limiting agent of transport processes | Boundary between mobile regolith and bedrock defines portion of the landscape available for transport under available surface processes |
| Tar sands expansions | -new in-situ mine -reclaimed pond in river bend -new tailings ponds -more roads -overall, more deforestation -much bigger area has been mined |
| Chesapeake bay | -Sediment & phospherous being delivered to the bay -130 m/my -global is 16 m/my -flux out of soil is greater than the flux in |
| Mining pit | -2km diameter -deepest part is 1 km -volume of a cone = pi r^2 h/3 -1 km^3 -largest landslide in NA history |
| german lignite mine | -bigass moving buildings -9 million kg of stuff/hr -sunken gardens is 100*2*25 volume -& sediment is 1500 -6000 * 1500 = 9mil -so the bagger could create the sunken gardens in an hour |
| Stuff being moved per capita | -exponential increase -but world is a lot lower than USA average |
| land area usage | -forest decreased -cropland, pasture & urban increased • pasture & cropland increased but went down over the last decade • we’re reaching the carrying capacity of arable land -population grew exponentially -humans have modified at least 1/2 of earth |
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