Spring was making itself heard in the Chugach Mountains south of the Matanuska Valley in Alaska. Among the bright new leaves of birch and the dark branches of spruce that shared the flats below the Knik Glacier, the songs of resident and migrating birds resounded. Swallows, thrushes, siskins, and warblers flitted through the trees, and joyful chirps of celebration filled the newly warm air of the season. Kingfishers and crows punctuated the chorus in raucous lower tones. Infrequently, from its perch on a tall spruce, a raven dropped an unusual bell-like tone or injected a grumpy complaint into the chorus, resentful of the invaders that now intruded on a territory it had claimed all winter.
Adding to the cacophony, melt from snow that had slowly receded to the rocky slopes of the high peaks above the tree line on both sides of the valley provided sustained background music in dozens of streams and waterfalls. Runoff poured down steep hillsides, tumbling pebbles with gleeful burbles and cleaning out last year's hoard of fallen leaves in its rush to join other rivulets in carving larger, deeper furrows into lower ground. Cutting through the gravel and sand of long-departed ice fields, ribbons of water twisted their way into the upper reaches of the Knik River, raising its flow to cover bars and banks the cold months had left dry and bare.
High above the river flats, beyond the steep flank of Mount Palmer, the Knik Glacier rose at five thousand feet in a giant ever-retreating river of ice that scoured a path, grinding away at the mountains through which it ran, moving inexorably if imperceptibly, sculpting out a channel between the ridges. Each winter's cold slowed its motion, and snow added to its bulk. Still it moved forward into the river valley at an angle that brought its foot into solid contact with the slope of Mount Palmer, forming a dam of ice that closed off part of its own melt and that of several smaller glaciers that surrounded Lake George immediately to the west.
In the spring, when the snow and ice began to melt again, this dam contained the resulting water, which backed up and gradually filled the lake until it extended far beyond its winter boundaries. As summer set in and the weather grew warmer, the glacial dam would become unstable and periodically calve away in great towers of dense ice hundreds of feet tall, which would fall crashing into the lake with a roar that reverberated between the peaks.
Where glacier and mountain met to form the dam, water was already gradually finding its way into a narrow crack between the two. Just a few drops followed each other through the opening first, melting ice as they ran, widening the passage until their drip became a trickle. Soon it would be a stream. Then, finally, with a huge grinding rumble, the weight of thousands of gallons of water would become too much for the weakening dam and break it apart. Carrying chunks of the ice that had contained it, floodwater would pour into the valley below with a force that had been known to tear out the bridges and roads of early settlers. In March of 1964, the strongest earthquake ever recorded in North America severely shook South Central Alaska and altered the Knik River Valley terrain enough to moderate the yearly flood and lessen its force. The water still broke through with a roar that shook the ground and filled the river from bank to bank with roiling turbulence, but the destruction it had visited upon the works of man was reduced.
Even before this flood, however, the river rose dramatically with the spring melt and spread powerful icy waters over shallows and sandbars that had lain untouched and freeze-dried through the silent winter. Released from its...
