Rain gone, and in sun again we could hear the consumption of an island. Large pieces of the bank fell thunderously into the water, because the Yukon had decided to yaw. We passed a deep fresh indentation in the shore where a dozen tall spruce had plopped at once. They were sixty-foot trees, and so much of the ground that held them had fallen with them that they now stood almost vertically in thirty feet of river. Ordinarily, as a river works its way into cut-bank soil the trees of the bank gradually lose their balance and become “sweepers”—their trunks slanting downward, their branches spread into the water. The islands of the Yukon have so many sweepers that from a distance they look like triremes.
—John McPhee, Coming into the Country (1977), pp. 279-280