Discuss three factors that increase ground settling due to thaw ...

[segrsyd]

Discuss three factors that increase ground settling due to thaw in Arctic regions.
  What will be an ideal response?

Question 2

Why is groundwater mining linked to ground subsidence? Discuss the factors that create the subsidence and why the damage cannot be repaired.
  What will be an ideal response?

[quynhmickitran]

Answer to Question 1

ANSWER:
A successful answer will include at least three of the following.
- In warm summer months, upper layers of permafrost will thaw naturally.
- Climate change is increasing the extent and duration of this summer warming beyond what is expected in the affected regions.
- Large areas of water in lakes and rivers can heat the ground, causing thaw in nearby areas.
- The removal of vegetation that maintains deep snow cover can expose permafrost to more heat.
- Forest fires can add heat directly to the ground, thawing permafrost.

Answer to Question 2

ANSWER: Groundwater mining removes water from the subsurface aquifer for human use. Aquifers contain sand and gravel whose pore spaces are filled with water. When the water is removed, sand grains pack more tightly together. This decreases the volume of the aquiferous sand layer and causes subsidence over a large area. Clays and silts fill the pore spaces, so injection of water back into the aquifer cannot re-expand the sand layer and repair the subsidence. The large area affected also makes repair difficult.