Explanation:

 1.  Drumlin is inverted boat-shaped deposition in a till plain caused by glacial deposition.

 2.  Stalagmites is a mound or tapering column rising from the floor of a cave, formed of calcium salts deposited by dripping water and often uniting with a stalactite.

 3.  Barkhan is a crescent-shaped shifting sand dune, convex on the windward side and steeper and concave on the leeward.

4. Peneplain, gently undulating, almost featureless plain that, in principle, would be produced by fluvial erosion that would, in the course of geologic time, reduce the land almost to baselevel (sea level), leaving so little gradient that essentially no more erosion could occur.