Lecture 11 - Permafrost Flashcards
Subsidence?
A slow or rapid, nearly vertical, downward movement of Earth’s surface
Karst?
A common type of landscape associated with subsidence; resulting from the dissolution of limestone, dolotstone, marble, gypsum, or rock salt by groundwater
What causes soil expansion and contraction?
Changes in the water content of the soil
Freezing and thawing
What causes sinkholes?
Dissolution produces voids which join to form caves, and then sinkholes
Karst plain?
A surface pock-marked with a large number of sinkholes
What are the types of sinholes?
- Solution Sinkholes: formed by dissolution of buried bedrock along planes and fractures
- Collapse Sinkholes: collapse of surface or near-surface rock or sediment
What causes calcium carbonate to deposit on the sides, ceiling, and floow of caves?
Groundwater seepage
Tower karst?
Steep limestone pillars common in highly eroded karst regions (humid tropical regions)
Dissapearing streams?
Streams that flow from the surface into cave openings
Springs?
Natural discharges of groundwater at the surface (vulnerable to contamination)
What are the parameters for permafrost?
Soil or rock must remain cemented with ice for at least 2 years continuously
Types of permafrost?
- Continuous permafrost (temp less than -5)
- Discontinuous permafrost (covers 50-90% of ground, temp -4 - -2)
- Sporadic permafrost (covers less than 50% of ground, temp -2 - 0)
Active layer?
Top layer of soil which is not continuously frozen, due to changing surface temps
Piping?
Particles of silt and sand in the subsurface slowly carried by groundwater laterally to a sping, caused by groundwater creating tunnels as it percolates through loose sediments
Fine sediments?
- compacts when pore water is removed
- flooding replenishes it
- common on river delta