1 Prepare before your flight by getting a doctor's letter or note on a prescription pad, stating that you have an implanted metal object. Show this letter to security agents.  Tissue expanders will be overfilled, so your skin can stretch and drape when your permanent breast implant is placed.
If valley glaciers erode a mountain from several directions, a sharpened peak called a horn might form.
How Glaciers Form. Glaciers form when more snow falls than melts each year. Over many years, layer upon layer of snow compacts and turns to ice. There are two different types of glaciers: continental glaciers and valley glaciers. Each type forms some unique features through erosion and deposition. An example of each type is pictured in Figure below. 1  A continental glacier is spread out over a huge area. It may cover most of a continent. 2  A valley glacier is long and narrow. Valley glaciers form in mountains and flow downhill through mountain river valleys. (A) The continent of Antarctica is covered with a continental glacier. (B) A valley glacier in the Canadian Rockies.