The biggest US state is full of superlatives. Denali, the highest peak in North America at 20,320 feet, is still rising, pushed upward as a tectonic plate collides from the south. The collision has also created huge mountains along Alaska�s Gulf Coast, where humid coastal air has produced the largest subpolar icefield in North America. The exceptional heights of Alaska�s mountains are mirrored below sea level by the 22,377-foot-deep...