Surface Processes

• Name ways to measure rates of geomorphic processes. Sediment yield stageSediment volumesCosmogenic isotopesNatural basinsThermochronology
• What is weathering? The chemical or physical alteration of primary minerals (unaltered by weathering) that make up the parent material.
• What is regolith? Unconsolidated, weathered material
• What happens in physical weathering? Greater surface area = accelearated chemical weathering
• What happens in chemical weathering? Changes in mass or volume = promotes physical weathering.
• How is biological activity involved in weathering? Biological activity catalyzes both physical and chemical weathering: Depends on species, substrate and weathering processese.g. plant secrete organic acids and respire CO2 in soil, changing pHBioturbation (biological mediated mixing e.g. ants) bring back fresh rock into soil and creates pathways for reactive oxygenated groundwater
• What can we learn from weathering style, intensity, rates and relative proportion? Regional climate (latitude and elevation/topography)Presence, amount and phase of waterLithology (rock type)
• What happens if weathering outpaced erosion? Thick mantles of saprolite (chemically weathered, in-place rock that has lost mass and strength, but not volume) form.
• What happens when erosion outpaces soil production? Bedrock landscapes that influence form and ecology.
• Physical processes can cause disaggregation, what is that? Mechanical breakdown without change in composition.
• What is freeze-thaw? Expansion of water confined in fractures and pore spaces freezes and breaks rocks or along grains.Primary weathering in apline and polar regions e.g. felsenmeer
• What is thermal expansion? Expansion of rocks and minerals when heatedLow thermal conductivity of rock = low penetration of heatTemp difference between hot outer layer and cool inner layer = large differential stresses = spalling e.g. forest fires, solar heatingLarge coefficient of thermal expansion of minerals (e.g. calcite) can cause granulae disintegration e.g. grus formed from granitic rocks.
• How does wetting and drying affect rocks in weathering? Constant hydration and dehydration of minerals causes swelling or contraction, which fractures rocks ir disaggregates mineral grainse.g. anyhdrite to gypsum, clay minerals, expansive soils, micas, haliteDaily/seasonal cycles of wetting and drying (e.g. salt spray in coastal settings, evaporation in arid environments)
• The primary chemical weathering agent is... rainwater (and its dissolved ions) which provide essential nutrients to the biosphere).
• Primary minerals weather to elements in solution and form... seconfary minerals more stable at Earth's surface (e.g. clays, hydrous oxides)
• How is mineral stability involved in chemical weathering? Mineral weathering suspectibility inverse sequence in which they formed deep within the Earth Mafic minerals weather more rapidly than felsicSImple-covalent structures (e.g. quartz) more resistant to weathering than complicated ionic-bond silicates
• List the following cation s in order of mobility (from least to most): Si4+ , Na+ ,K+, Ca2+ , Al3+, Fe3+, Mg2+, Fe2+ Ca2+, Na+, Mg2+ > K+ > Fe2+ > Si4+ > Fe3+ > Al3+
• What do oxidation and reduction form in soils? Oxidation - FIrst form of weathering, forms hydroxides (insoluble and immobile)Reduction = FOrms more soluble and mobile elements
• What are the two most important factors in terms of solutions chemically weathering? FLow rate and acidity of pore water
• What is the difference between congruent dissolution and incongruent dissolution? Congruent = All remain in solutionIncongruent = Released ions form compounds and secondary minerals e.g. insoluble Fe and Al oxides accumulate over time)
• Hydrolysis in soil results in incongruent dissolution of aluminosilicate minerals into clay minerals or oxides. What are examples of aluminosilicate minerals? Feldspars and micas
• aluminosilicate + H2CO3 + H2O --> Compleye the equation and why is it important? clay mienral + cations + HCO3- + H4SiO4 Earth's long term-climate is mediated by silicate weathering and organic matter burial
• What is pedogenesis and how does it occur? Pedogenesis is soil formationOccurs by addition, loss, transformation and translocation (movement from one part of a profile to another) of material within a profile.
• Pedogenesis is controlled by... ClimateBiological activityTopographyParent materialTime
• How does pedogenesis differ in tropical regions and arid regions? Tropical regions = Hotter, more water = More weathering = Thocker soils and more stable weathering products (kalonite clay and Fe/Al minerals); Polar regions, soils thin and minimal chemical alterationArid = Mid-latitiude temp = intermediate soil depth and weathering intensity, carbonate or salts precipitate and accumulate through time
• What are the 2 fundamental characteristics in precipitation? DurationIntensityGeomorphically effective when it exceeds intensity-duration threshold that triggers event (landslide)
• What is the recurrence interval (RI) and how do you calculate it? The probabilty of an event based on average time between events of at leasr a certain magnitude.Requires many observations of different maximum events over time. Each maximum is assinged a rank based on its magnitude.RI = (N + 1)/rInvolves extrapolation abd assumption of stationarity, hence introduces uncertainty.
• What is evapotransportation (ET)? Part of precipitation that doesn't contribute to runoffA flux of moisture to atmosphere both through physical evaporation and biological transportationControlled by temperature, relative humidity, wind speed, intensity of solar radiationVaries in space and time e.g. seasonal diurnal inputs of solar radiation, and type of vegetationCan remove 1/2 of the precipitation and draw down water table during growing season
• Groundwater maintains baseflows (flow between storms) and geomorphic effects, e.g. ... WeatheringLikelihood of mass movementsSurface water flowpathsType and distribution of vegetationRate and distribution of surface erosion
• What is soil infiltration rate? How quickly water moves into soil
• Precipitation infiltrates into the vadose zone, what is this? Unsaturated area, contains air.
• Define: Water tableCapillary fringe Water table - Pore spaces filled and water flows freelyCapillary fringe - Pores filled, but capillary forces enough to stop flow
• What is a hydrograph? Chart of volume of water moving through a channel (discharge) through time, with common diagnostic characteristics: Baseflow (between storms)Peak discharge (max storm)Rising limb (flow rapidly increasing)Falling limb (flow slowly decreasing)Lag-to-peak, delay between rainfall and runoff
• Complete the sentences: Hillslope composition (bedrock vs soil mantled) controls ... and ..., which influences the ... and ... of hillslopesHillslope parameters control processes of ..., and are important for understandind geologic ... associated with ...Fluvial systems are influenced by regional landscape parameters including ... that move water and sediment into and through stream channels.Fluvial processes can be described and quantified with an understanding of the physics that governs the frequency of changes in velocity and discharge of water, and thus stream power, that drives erosion. ...
• Define angular velocity (provided a body is rotating its angular velocity) The angle turned through divided by time taken.
• What is the moment of inertia? What does it depend on? A measure of the way in which a body's mass is distributed in relation to the axis about which its rotating. Depends on mass, size, shape and axis.
• How do you calculate torque? Force x perpendicular distance of line of action of the force from the axis.
• What is the principle conservation of angular momentum? The total angular momentum of a system is constant unless an external torque acts on it.
• Centrifugal force is... ... an outward force apparent in a rotating reference frame. It doesn't exist when a system is described relative to an inertial frame of reference.
• Centripetal force is... ... a real force that acts in an inertial reference frame to cause a body to move along a circular path, and acts towards the centre of rotation.