Permafrost and Subsidence

Question 1

What is subsidence?

Answer 1

The slow or rapid almost downward movement of earth

Question 2

What is Karst?

Answer 2

Landscape resulting from dissolution of limestone, dolostone, marble, gypsum or sock salt

Question 3

What does soil expand and contract?

Answer 3

Changes in water content

Freezing and thawing

Question 4

True or false: subsidence is one of the most widespread and costly natural disasters?

Answer 4

TRUE

Question 5

What is a karst plain?

Answer 5

Terrain pocketed with lots of sinkholes

Question 6

What is a collapse sink hole?

Answer 6

collapse of surface sediment

Question 7

What is a solution sink hole

Answer 7

Caused by breakdown of underlying bedrock on planes or fractures

Question 8

How are caves formed

Answer 8

A series of subsidence, due to changes in the water table

Question 9

What is formed by the water responsible for forming caves?

Answer 9

Calcium will deposit on the walls and will form flowstone, stalagmites and stalactites

Question 10

What is the difference between a stalagmites and a stalactites

Answer 10

stalagmites grow up from ground

stalactites hang from the ceiling

Question 11

How is flow stone formed?

Answer 11

From water flowing and carving patterns

Question 12

What is tower karst?

Answer 12

Highly eroded karst regions, common in humid tropical regions

Question 13

What are disappearing streams

Answer 13

streams that flow from the surface into mouths of caves

Question 14

What are springs?

Answer 14

discharge of ground water to the surface, very susceptible to contamination

Question 15

what is permafrost?

Answer 15

Soil that has remained cemented in ice for at least 2 years

Question 16

What is continuous permafrost

Answer 16

Mean annual temperature is less than -5 degrees

Question 17

What is discontinuous permafrost?

Answer 17

Covers 50-90% of the landscape, mean annual temperature between -4 and -2 degrees

Question 18

What is sporadic permafrost?

Answer 18

Covers less than 50% of the landscape, mean annual temperature between -2 and 0 degrees

Question 19

What is the active layer?

Answer 19

thaws in spring and re freezes in fall

Question 20

What happens to the ground when perm frost thaws?

Answer 20

It can cause subsidence, when there is a lot of thawing it causes thermokarst

Question 21

What happens to frost susceptible sediment when it freezes

Answer 21

It expands causing frost heaving

Question 22

What is piping

Answer 22

Particle of silt and sand carried in groundwater laterally to a spring

Question 23

What is piping caused by. Where is it common

Answer 23

Groundwater creating tunnels as it moves through loose sediment, in silt and sand sediments

Question 24

How do fine sediments compact?

Answer 24

By the removal of pore water, common on river deltas

Question 25

How do collapsible sediments compact?

Answer 25

They dissolve in water or have loose bonds, arid regions

Question 26

How do organic sediments compacted?

Answer 26

wetland soil contains a large amount of water and compacts when water is drained

Question 27

What is expansive soils?

Answer 27

Soils that expand when wet and contract when dry, common in clay rich soil containing smectite

Question 28

What is the link between earthquakes and subsidence

Answer 28

earthquakes can lower ground surface, costal subsidence can cause flooding, magma uplifts volcano during eruption and after the chamber empties surface subsidence

Question 29

What regions are at risk

Answer 29

landscaped with soluble rocks or permafrost or easily compacted sediment, soils with lots of smectite clay and silt is very securable to first heaving

Question 30

What are some ways humans cause subsidence

Answer 30

Underground mining, permafrost thawing, withdraw of fluids (oil, natural gas etc.), restriction of deltas via dams etc. draining wetlands, landscaping on expansive soil Ex. addition of plants changes water levels