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.
Two valley glaciers flow around a small horn and merge together to form a larger valley glacier. Once upon a time, the larger valley glacier flowed down the whole length of the valley, carving out a U-shaped valley. The glacier is in retreat because only a portion of the glacially carved, U-shaped valley contains ice.