Lecture 11 - Permafrost Flashcards

1
Q

Subsidence?

A

A slow or rapid, nearly vertical, downward movement of Earth’s surface

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2
Q

Karst?

A

A common type of landscape associated with subsidence; resulting from the dissolution of limestone, dolotstone, marble, gypsum, or rock salt by groundwater

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3
Q

What causes soil expansion and contraction?

A

Changes in the water content of the soil

Freezing and thawing

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4
Q

What causes sinkholes?

A

Dissolution produces voids which join to form caves, and then sinkholes

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5
Q

Karst plain?

A

A surface pock-marked with a large number of sinkholes

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6
Q

What are the types of sinholes?

A
  • Solution Sinkholes: formed by dissolution of buried bedrock along planes and fractures
  • Collapse Sinkholes: collapse of surface or near-surface rock or sediment
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7
Q

What causes calcium carbonate to deposit on the sides, ceiling, and floow of caves?

A

Groundwater seepage

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8
Q

Tower karst?

A

Steep limestone pillars common in highly eroded karst regions (humid tropical regions)

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9
Q

Dissapearing streams?

A

Streams that flow from the surface into cave openings

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10
Q

Springs?

A

Natural discharges of groundwater at the surface (vulnerable to contamination)

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11
Q

What are the parameters for permafrost?

A

Soil or rock must remain cemented with ice for at least 2 years continuously

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12
Q

Types of permafrost?

A
  • 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)
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13
Q

Active layer?

A

Top layer of soil which is not continuously frozen, due to changing surface temps

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14
Q

Piping?

A

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

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15
Q

Fine sediments?

A
  • compacts when pore water is removed
  • flooding replenishes it
  • common on river delta
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16
Q

Collapsible sediments?

A
  • Loess and some stream deposits in arid regions are loosely bound or are water soluble
  • water weakens bonds = compaction
17
Q

Organic sediments?

A
  • wetland soils contain large amounts of orgnaic matter and water
  • water drains/soil decomposes, soils compact
18
Q

Expansive soils?

A

Expand during wet periods and shrink during dry periods

  • common in clay, shale, clay-rich soil w/smectite
  • produces dissication cracks
19
Q

Desiccation cracks?

A

cracks fromed when all the water is removed from the soil

20
Q

What natural phenomenon has been lowering the coasts of Vancouver Island, Washington, and Oregon?

A

Earthquakes

21
Q

How does magma cause subsidence?

A

When a volcanoe erupts, the magma chambers are emptied and the ground sinks

22
Q

Frost heaving?

A

Upwards well of soil during freezing conditions as ice grows towards the surface
- soils containing silt are susceptible

23
Q

What are the effects of permafrost thaw?

A
  • roads cave in
  • airport runways fracture
  • buildings crack/tilt/collapse
24
Q

What contributes to the sinking of New Orleans?

A

coastal flooding and loss of wetlands along the mississipi delta

25
Q

What are some natural service functions caused by subsidence?

A
  • karst regions contain the world’s most abundant water supply
  • aesthetic
  • scientific resources
  • unique ecosystems (aka cave dwellers)
26
Q

What are signs of subsidence?

A
  • cracks
  • hummocky grounds
  • closed depression