Beaufort Sea Boulder Patches

For the most part, the shallows of the Beaufort Sea have a mud and silt bottom. The one known exception is just east of Prudhoe Bay in the shallows of Stefansson Sound. There, in a 160-square-mile area between the shore and Cross and Narwhal Islands, is a group of boulder patches.

Rocks up to a meter (3 feet) litter the seafloor. Where they came from and how they got there no one knows. Possibly they were carried out of the mountains to the south by glaciers during a past glaciation. Or perhaps they were rafted into their location on top of ice fragments originating in the Greenland or Ellesmere Island ice sheets, thousands of years ago.

Compared to most of the rest of the floor of the Arctic Ocean, the boulder patches are teeming with life. Like a tropical coral reef, each boulder patch supports a community of kelp and other attached plants and animals, along with various fishes and invertebrates that move around among the boulders.

Originally, the boulder fields and their associated living populations were discovered by scuba-diving scientists from the University of Alaska's Institute of Marine Sciences back in the 1960's. Now, there is renewed interest in these anomalous patches because they lie right in the middle of a proposed lease sale area for oil and gas exploration. In fact, they comprise about 20 percent of the area of a joint lease sale proposed by Alaska and the federal government in December 1979. For this reason, the Stefansson Sound boulder patches will be in the news in the months ahead.