Columbia Glacier Melt, Alaska
"Alaska's Columbia Glacier descends through the Chugach Mountains into Prince William Sound. When British explorers surveyed the glacier in 1794, its nose extended to the northern edge of Heather Island, near the mouth of Columbia Bay. The glacier held that position until 1980, when it began a rapid retreat. The glacier has thinned so much that the up and down motion of the tides affects its flow as much as 12 kilometers (7.5 miles) upstream, until the glacier bed rises above sea level and the ice loses contact with the ocean."