Subsidence Flashcards
Venice is ____ because it is built on _____, ______ sediment
- sinking
- loose, muddy
subsidence is slow or rapid, nearly _____ downward movement of _______
- vertical
- Earth’s surface
karst is ______ resulting from ______ of limestone, dolostone, marble, gypsum or rock salt
- landscape
- dissolution
soil expansion and contraction is due to changes in _________ of soil as well as _____ and ______
- water content
- freezing
- thawing
sinkholes in large numbers form a ______
karst plain
karst is a common type of landscape associated with ______
subsidence
rocks are dissolved by _____ or ______
- surface
- groundwater
dissolution produces ____ which join to form caves and ______
- voids
- sinkholes
sinkholes can range from ________ in diameter
1 to 100’s of metres
solution sinkholes are ____ formed by solution of ____ _____
- pits
- buried bedrock
a collapse sinkhole is ______of ____ or near-_____ rock or sediment
- collapse
- surface
sinkholes damage:
- highways
- homes
- sewage facilities
cave systems are formed when _____ produces a series of ______
- dissolution
- caves
groundwater seepage in cave systems causes:
- flowstone
- stalagmites
- stalactites
tower karst is created in highly ______ karst regions
eroded
disappearing streams occur when streams disappear into ____ ____
cave openings
springs occur where ______ naturally flows onto the ______
- groundwater
- surface
caves create direct access between ____ and ______
- surface
- groundwater
permafrost is when _____ or _____ has been frozen for at least ____
- soil
- sediment
- 2 years
the active layer in permafrost _____ in winter and _____ in summer
- refreezes
- thaws
when permafrost thaws, it can create ____ _____
land subsidence
extensive thawing of permafrost creates _____ soil called ______
- uneven
- thermokarst
permafrost is continuous if its mean annual temperature is less than _____
-5 degrees C
sediment piping is ______ moving through _______
- groundwater
- loose sediment
removing groundwater through pumping can result in ______ of land due to ______ of pore space that was occupied by _____ and supported by the _____ _____
- subsidence
- collapse
- water
- water pressure
fine sediment ______ when pore water is removed, and is common on ____ ______
- collapses
- river deltas
organic sediments are when _____ soils contain large amounts of _____ matter and ____
- wetland
- organic
- water
expansive soils commonly have _____ and _____ during wet periods and _____ during dry periods
- clay
- expand
- shrink
human causes of subsidence:
- underground mining
- water withdrawal
- melting permafrost
- restricting deltaic sedimentation by constructing dams
how to minimize subsidence hazard:
- restrict fluid withdrawal
- regulate mining
- prevent damage from thawing permafrost
- controlled flooding to rebuild marshes
