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.
Continental glaciers are huge. They may spread out over much of a continent. Valley glaciers are long and narrow. They form in mountains and flow through mountain river valleys. Glaciers cause erosion by plucking and abrasion. Valley glaciers form several unique features through erosion, including cirques, arÃªtes, and horns.