The Unstable Earth

The question of who owns the land uncovered by a retreating glacier near Juneau came into the news recently. Since we tend to think of geological changes as being slow, questions such as this might seem, at first glance, to be relatively unimportant. Yet, Alaska's high level of tectonic activity, coupled with the effects of climatic change, can alter the geography rather rapidly. New land created by some but not all of these changes belongs to the public rather than to those who own adjacent property.

Earthquakes and volcanic eruptions, of course, can create big changes in a short time. The violent earthquakes of September 3 and 10, 1899, created major changes in the shorelines around Yakutat Bay. In some places the beaches subsided, in others they raised; the earthquake created the world record for uplift--47 feet, 4 inches--at a location on the west shore of Disenchantment Bay, which lies at the head of Yakutat Bay.

During the 1964 Good Friday earthquake, much of Cook Inlet and the Kenai Peninsula subsided by distances ranging from near zero on the west side of the inlet to six feet on the east side of the peninsula. Off to the southeast, parts of Montague Island rose 30 feet. Horizontal movements as great as 70 feet accompanied the sinking and rising. During the event, the Matanuska Valley grew about five feet wider.

More subtle are the elevation changes that evidently proceed more-or-less continuously. The teacher of a surveying course I once took told about the troubles had by a crew running a level-line from the Gulf of Alaska to Big Delta, some years ago. One summer they ran the line to Big Delta. The next year, they ran back the other way, only to find that their survey failed to close by about four feet. A more speedy repeat of the work demonstrated that the land in the Interior was rising relative to the coast. Hence, the moving land, not faulty work, was responsible for the failure to close the survey.