geological terms
Had to look these terms up in Wikipedia. From the Maine Gazetteer‘s listing of unique natural features.
esker
An esker is a long winding ridge of stratified sand and gravel, examples of which occur in glaciated and formerly glaciated regions of Europe and North America. Eskers are frequently several miles long and, because of their peculiar uniform shape, are somewhat like railroad embankments.
monadnock
A monadnock or inselberg is an isolated rock hill, knob, ridge, or small mountain that rises abruptly from a gently sloping or virtually level surrounding plain. The term “monadnock” is usually used in the United States, whereas “inselberg” is the more common international term. In southern and southern-central Africa, a similar formation of granite is known as a kopje, a Dutch word from the Afrikaans word: koppie.