periglacial hazards Flashcards
what is the classification of clod region hazards?
ground instability impact and burial- snow avalanches and permafrost. few fatalities but economic costs are very high and it is increasing.
what are factors that enhance the potential hazardousness of permafrost?
irregular permafrost distribution high permafrost temperature high ice ground content thick, moist active layer steep slopes
what are factors that enhance human risk to permafrost hazardousness?
high population density and vulnerability
valuable infrastructure located on permafrost
inadequate engineering regulation
what is periglacial?
cold but not glacial- ground ice rather than glaciers.
what is permafrost?
physical state. the more you build on it, the more hazardous.
what layers do permafrost consist of?
active layer and permafrost, plus unfrozen areas called talik.
what are the main types of permafrost?
continuous, discontinuous, and sporadic and isolated.
what percentage of frozen is continuous?
90-100% frozen
what percentage of frozen is discontinuous?
50-90% frozen
what percentage of frozen is sporadic?
10-50% frozen
what percentage of frozen is isolated?
0-10% frozen
why are snow avalanches so dangerous?
due to velocity, shortness of time between initiation and impact etc
what is the density core like in an avalanche?
from 50 to 100 km/m cubed. consist of dense avalanche core and suspension layer
how do you measure the speed of avalanches?
hard to measure. related to the amount of vertical fall and wetness of snow.
how are avalanches classified?
according to: triggering mechanism type of rupture position of sliding surface humidity
what are the 2 main types of avalanches?
lose snow, and slap-avalanche
what are the 2 main controls of snow avalanches?
meteorology and terrain
how does meteorology control avalanches?
how much snow, where it falls, where snow accumulates. what happens after fall by changing temperature and moisture that can change crystal structure and snowpack stability.
how does terrain control avalanches?
slope angle, aspect, roughness (trees etc)
what are the impacts of snow avalanches on infrastructure?
breaks windows, push in doors, destroys wood-framed structures, uproots mature spruce trees, move reinforced concrete structures.
what are mitigation measures of avalanches?
mapping and hazard zoning, terrain engineering, avoidance and evacuation
how can you live with avalanches?
permanent snow supporting structures temporary snow supporting structures snow drift measures avalanche dams direct protection of buildings forest
what are examples of direct protection of buildings?
avalanche splitter and reinforced walls.
what are examples of avalanche dams?
catching dams, deflecting dams, breaking mounds.
what are examples of snow drift measures?
fences, and wind baffles.
what are permafrost hazards?
bedrock and sediments.
what is bedrock?
non-competent lithologies, competent well joined lithologies, competent massive lithologies.
what is sediment?
fine grained and corse-grained.
what are triggers for permafrost degradation and hazards?
vegetation (human and natural), climate, geomorphology.
what happens when ground ice melts in permafrost?
active layer thickens, ground ice melts, ground subsides organic matter frozen in permafrost begins to bet and release greenhouse gases.
why does permafrost melt?
when ice rich permafrost melts, there will be a loss of volume. ground stability decreases even with partial melt and permafrost warming.
what are key factors of permafrost melting?
low altitude, frequency of large flood plains, areas of relatively high population.
what are types of management for lowland periglacial hazards?
hazard mapping, geotechnical engineering, thermosyphons, piling, insulation.
what fraction of the world does permafrost cover?
1/4
why are highland events increasing and becoming more extreme?
due to the nature and consequences of periglacial hazards reflecting the amount of energy released.
what holds a crucial role in determining the temperature and moisture drivers of all relevant periglacial processes?
seasonality.
what is permafrost?
permafrost is ground, including rock or (cryotic) soil, with a temperature that remains at or below the freezing point of water 0 °C (32 °F) for two or more years.
where is permafrost located?
Most permafrost is located in high latitudes (in and around the Arctic and Antarctic regions), but at lower latitudes alpine permafrost occurs at higher elevations.
is ground ice always in permafrost?
Ground ice is not always present, as may be in the case of non-porous bedrock, but it frequently occurs, and it may be in amounts exceeding the potential hydraulic saturation of the ground material
