Answer to Question 1
Periglacial regions occupy over 20 of the Earth's land surface and are dominated by the geomorphological processes related to the freezing of water. Periglacial conditions occur at high latitudes, with a near permanent ice cover, at high elevations in lower latitudes, with areas that are seasonally snow free. They tend to correspond to subarctic and polar climate zones, in particular the tundra climate.
In areas where the soil, sediment, or rock is below freezing for at least two years, permafrost forms. Where permafrost is not covered by a glacier, it is considered periglacial. Large portions of Alaska, Canada, China, Scandinavia, Greenland, and Antarctica have permafrost. Permafrost may be divided into continuous and discontinuous zones and are exactly as the names suggest.
These periglacial environments are subject to freeze/thaw actions and the landforms that result, such as ice wedges, hummocks, patterned ground, solifluction, and gelifluction. Humans have also settled periglacial regions. Due to the freeze/thaw processes, humans must learn to properly adapt structures to the environment.
Answer to Question 2
In order for limestone to develop into karst topography, it must contain 80 or more of calcium carbonate, it must have a complex patterns of joints and an aerated zone; and vegetation must be present. Common features of karst topography include sinkholes (dolines), karst valleys; cockpits and cones; caves and caverns; and (within caves and caverns) the varied speleothems.
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