Term
| what are the qualities of rocks broken during tectonic uplift, exhumation, distortion? |
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Definition
| the qualities of rocks broken during uplift, tectonic distortion, and exhumation is that they are broken at large-scale but intact down to silt size |
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Term
| describe rocks broken during surface mass movements/faulting |
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Definition
| rocks broken during surface mass movement or faulting can range from small boulder to nanometer size. it depends on stress and strain. large landslides often generate a lot of fine debris |
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Term
| the two ways rocks can break |
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Definition
| the two ways rocks can break is collapse, or dynamic fragmentation |
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Term
| what is the strain/stress conditions related to rock breaking via collapse? what about the KE it produces? |
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Definition
| rock collapse occurs under relatively low stress/strain, and produces relatively little KE. KE from breaking rocks is the fragements flying out at high velocity |
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Term
describe the process of dynamic fragmentation
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Definition
the process of dynamic fragmentation
1. first, a rock particle is put under high stress by a landslide or fault
2. the stress deforms the particle. this deformation causes the particle to store elastic strain energy
3. when the stress reaches the elastic limit of the rock, denoted as Q, internal failure surfaces form. this releases the strain energy, and then the bits of the particle return to thier original shapes
4. the rock explodes, high KE because bits are moving fast. magnitude of dispersive stress = Q/3 |
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Term
| dominant size of mass movement: over long time periods, which tends to move more sediment: large landslides or small landslides? |
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Definition
| dominant size of mass movement: over long time periods, large landslides tend to move more sediment than small landslides. |
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Term
| most of the broken rocks on/in the ground were put there by landslides. what size landslide most likely put that broken rock there, knowing nothing else? |
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Definition
| the dominant form of mass movement for broken rocks is large landslides. even though large landslides are less frequenct than small ones, they move enough mass to compensate |
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Term
| what is the difference between loose granular flow and dense granular flow? |
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Definition
| the difference between loose granular flow and dense granular flow is that dense granular flow is under a high confining pressure that packs the grains together |
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Term
| both dense and loose granular flows involve distinct releases of energy that has built up |
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Definition
| in loose granular flow, energy built up is released as fragment kenetic energy when grains break. in dense granular flow, energy is released as transient elastic strain energy and travels through the grains as P and S waves |
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Term
| what is transient elastic strain energy? |
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Definition
| transient elastic strain energy is how dense granular flows release built up energy. the energy propogates through the grains as a wave |
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Term
| what is an example of a dense granular flow in nature? |
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Definition
| a rock avalanche is an example of naturally occuring dense granular flow |
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Term
| affect of rockfalls on glaciers |
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Definition
| the affect of rockfalls on glaciers is that when rocks cover the top of a retreating glacier and stop melting, the glacier reverses it's retreat and starts to move forward, leaving a moraine |
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Term
| when rockfalls trigger glaciers advances, what often goes makes up the moraine the glaciers make? |
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Definition
| A rockfall triggers glacier advance. The moraine formed consists of rockfall debris |
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Term
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Definition
| ablation moraine is a moriane caused by rockfall. Rockfall causes reflection of sun's energy, which is ablation |
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Term
| ablation moraines have no ______significance |
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Definition
| ablation moraines aren't connected to our climate history, they have no paleoclimatic significance |
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Term
| how do we test if moraines are paleoclimatic or ablation-related? |
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Definition
| we can test the cause of moraines by testing the sediment |
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Term
| what do we look at in moraine sediment to see if they are paleoclimatic or ablation? |
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Definition
| to see what caused a moraine, we focus on it's microsedimentology |
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Term
| debris from large landslides has grain size down to ____ and forms ____ |
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Definition
| debris from large landslides has grains on nanometer scale. large landslides like to form agglometerates |
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Term
| the key to understanding the sediment balance between tectonic uplift and erosion |
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Definition
| the sediment balance between tectonic uplift and erosion is that tectonic uplift-erosion=Δ land height. Davies teaches that these two things happen at the same rate, so change to land height is zero |
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Term
after earthquakes and landslides, the shape of a river may change, and this could affect the coast. How? (multiple step process)
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Definition
how earthquakes and landslides changing river path affect the coast:
1. earthquakes/landslides dump sediment into river's path, disrupting it's filuvially-optimal path.
2. as the river gets back it's it's optimal path, it erodes the dumped sediment downshore
3. the sediment is dumped at the coast, the coast progrades |
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Term
relationship between slope steepness and sediment storage:
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Definition
| the relationship between slope steepness and sediment storage is that when a slope is steep we say it has little sediment storage |
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Term
| four independent variables that determine river morphology |
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Definition
four independent variables that determine river morphology
1. sediment supply, which is defined by the amount of tectonic uplift
2. rainfall
3. geology
4. base level i.e. the coast |
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Term
| when they used stopbanks to cut the Waiho river off from 70% of it's fanhead, what happened? |
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Definition
| when the Wahio was cut off from 70% of it's fanhead by stopbanks, it aggraded and steepened to be able to transport the same amount of sediment it could before |
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Term
| takeaway from Kowhai and Hapuku river lesson |
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Definition
| the takeaway from the Kowhai and Hapuku rivers unit was that sea level rise can mean aggredation or incision depending on the state of the river |
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Term
| when europeans first came to NZ, they brought thier european river management with them. why didn't it work so well in NZ? |
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Definition
| when europeans came to NZ, they they brought the idea of using stopbanks to control rivers. this works ok when tectonic uplift is slow, and rivers bring less sediment (remember, the sediment that comes down = tectonic uplift). NZ rivers carry enough sediment to overwhlem stopbanks |
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Term
| how does the amount of sediment rivers carry relate to how they overwhlem stopbanks? |
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Definition
| one of the ways rivers overwhelm stopbanks is aggradation. they build up so much sediment that they overflow during floods |
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Term
| how are low land values connected to river management? |
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Definition
| the higher value the land, the more money you have to protect it. in other countries, they can afford cement stopbanks. in NZ, there simply aren't enough people for that level of infrastructure. so we have gravel stopbanks |
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Term
| tectonic uplift and erosion are in a dynamic equilibrium that stays at steady state, except for infrequent, short-term variations. what are these? |
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Definition
| the steady state is interrupted by earthquakes that can cause erosion of 30 years worth of sediment in a short time |
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Term
| when you alter a river, you reduce it's _____ |
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Definition
| when you alter a river, you reduce it's ability to carry sediment. This is called the bedload capacity |
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Term
| Kosi Fan, India. Case study of what? |
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Definition
| Kosi Fan, India is an example of river management gone wrong. they tried to put control banks on a river coming out of the himalayas, it aggraded and displaced 3 million people in 2 weeks |
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Term
| what did they do in the lab to confirm the theory that the stopbanks were causing aggradation on the Waiho? |
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Definition
| to test the theory that stopbanks were causing aggradation of the waiho, they built a microscale model of the river and added and took away stopbanks at will. doing this confirmed the theory |
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Term
| Hermitage village is an example of what phenomenom? |
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Definition
| Hermitage village was built in an area with flood control measures. Doing this restored the risk. this is a great example of how trying to reduce vulnerability can be a rat race because it encourages people to build more |
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Term
| the NZ flood risk process standard says what? |
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Definition
| the NZ flood risk process standard says that we need to understand the way that our river management is going to affect river path. we also need to understand the geomorphology that makes the river the way it is |
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Term
| sustainable river management means doing what after you build stopbanks? |
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Definition
| to sustainably bottle up a river with stopbanks, you must manually remove the sediment being built up and put it back in downstream |
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Term
global change on floods risk. explain
1. climate change
2. societal |
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Definition
global change and flood risk
1. it's really hard to predict how global climate change will affect river management.
2. it's really easy to see how societal change can/will affect river management. population growth, and the development that comes with it, will increase flood risk |
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Term
| what do we need to improve on with flood management laws in NZ? |
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Definition
| flood management laws have a good start with the NZ managing flood risk process standard. but, it won't do much until that kinds of rules get into lower-level nitty-gritty regulations |
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Term
| are slopes initiated or modified? |
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Definition
| slopes don't start flat. they are modified, not initiated |
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Term
2 slope modifacation processes
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Definition
2 slope modifacation processes
1. weathering
2. denudation |
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Term
| what does it mean for a process affecting a slope to be endogenic? |
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Definition
processes affecting a slope that are endogenic don't come from an external source. they come from the slope itself.
Endogenic processes don't move slopes, they just make them less steep |
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Term
| what does it mean for a process affecting a slope to be exogenic? |
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Definition
| to say a process affecting a slope is exogenic is to say it comes from an external source. some examples are rivers, and coastal erosion. exogenic processes can move slopes around, unlike endogenic processes |
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Term
4 processes that weather rock
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Definition
4 processes that weather rock
1. freeze-thaw
2. plant roots
3. chemistry
4. stress |
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Term
| what is denudation in the context of slope processes? |
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Definition
| denudation when we talk about coast processes is stuff sliding or flowing down a hill |
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Term
| denudation can occur two ways |
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Definition
| deundation can occur via stuff sliding or flowing down the hill |
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Term
| mass movement stability: slope failure occurs along ____ path |
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Definition
| slope failure occurs along a circular path. like a cycle wheel with a weight on it |
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Term
| two ways to increase factor of saftey of a slope that we talked about. |
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Definition
the two ways to increase the factor of saftey of a slope that we talked about is
1. take out moisture to increase friction via soil drainage
2. restribute mass from top to bottom. this is only really an option for slopes we have built |
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Term
| what's the hard part about finding the factor of safety for a slope? |
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Definition
| the hard part about finding factor of safety for a slope is finding frictional force, and the radius of the circular path you think it will fail along |
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Term
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Definition
| when rockfall of 90% rock acts like a fluid |
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Term
| stability analysis versus post-motion failure anaylsis |
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Definition
stability analysis is using the factor of safety to figure out if the slope is gonna fall.
Post-failure motion analysis tells us how the motion continues and where it will stop |
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Term
| why was the landslide on to black rapids glacier an interesting treaching point for post-failure motion analysis? |
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Definition
| the landslide on to the black rapids glacier was cool because the ice has a low coefficient of friciton, so the debris was going all over the place |
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Term
| slopes fail when? (from a physics perspective) |
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Definition
| slopes fail when gravity exceeds frictional force |
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Term
| what's the tool associated with post-failure motion anaylsis? |
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Definition
| post-failure motion analysis usually involves modeling the expected landslide |
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Term
| what do we call examining the way landslides move? |
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Definition
| examining the way landslides move falls under post-failure motion analysis |
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Term
| once we have figured out the liklihood and characteristics of possible landslides, we move to using that information to reduce risk. what are the two strategies for this? |
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Definition
the two ways to use information on landslide hazard to reduce risk:
1. create a number of landslides scenarios where proposed or existing human development would be affected
2. develop of landslide probability distribution to see the big picture. once you see the big picture, it is easier to rationalize what risks must be accepted and which must be changed |
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Term
| what's the biggest issue with hard engineering ways to stop landslides? |
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Definition
| the problem with hard engineering ways to stop landslides is that when the landslides to inevitably come, they will be bigger and more destructive |
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Term
| tree-domimated hillsides vs grass-dominated hillsides: difference in makeup and landslides |
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Definition
| the soil under tree-dominated hillslopes is deeper. landslides from tree-dominated hillslopes are less frequent, but are larger |
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Term
| my house is at the bottom of a landslide prone grass-covered hill. I want to plant some trees on it. what are 3 |
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Definition
when considering the switch to trees to put off landslides, consider the following:
1. what is the difference between soil depth under grass and soil depth under trees? by planting trees, how much soil am I "adding"
2. how long will the transition take?
3. is bedrock weathered to soil at the same rate under grass and trees? what is this rate? |
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