Karst Topography is the landscaping of the or beneath the surface that creates a network between the two via erosional dissolution of carbonate bedrock, i.e. dolomite, limestone, ect. Karst Topography can happen between strata layers creating cave systems and sinkholes if the rock layer above the carbonate rock, caprock, is thin, this is known as interstratal karst. Another type of Karst, is called Kegel Karst, or joint controlled Karst which is when fractures or jointing of  carbonate bedrock at the surface creates a way for runoff water find it’s way into the bedrock form marvelous creations such as Karst Towers (China displays a perfect set of Karst Towers). This process of dissolution is not unknown for the story is foretold by the rocks themselves. It starts with rainwater, which falls down onto and into to which it betroths with materials in the ground containing Carbon Dioxide creating a special concoction of Dihydrogen Carbon Trioxide, or Carbonic Acid. Carbonate rocks such as say Limestone, are composed of calcite which is sensitive to this acid, causing it to react in the form of dissolution. So needlessly to say, in wet areas of the world you can expect to see Karst Topography. 

An Ice Sheet is a mass of glacial ice that is not restricted by landscapes which allows it cover much more ground area. 

I'm learning about plate boundaries. Again. And how they form volcanoes. And how earthquakes work. ahhhhhhh