Porky’s Prank Redux

Mt. Edgecumbe “erupting” April 1, 1974

It’s easily the most famous April Fool’s Day practical joke in Alaska history. The late Porky Bickar, of Sitka, Alaska, and a group of assistants, who mostly prefer to remain anonymous, helicoptered a couple of hundred old tires, some diesel fuel and a sterno can to the crater of Mt. Edgecumbe, an inactive volcano about 15 miles west of Sitka. On April 1, 1974, he set the whole mess off and, for a while at least, Sitkans thought Mt. Edgecumbe was erupting. This year will be the 50th anniversary of Porky’s RF, and folks in Sitka will still be talking about it.

Now the joke may be on Porky and his cohorts. Mt. Edgecumbe is showing volcanic signs of life, admittedly faint signs, but still.

There have been swarms of low level earthquakes, the signature of magma moving deep underground. And the ground near the volcano is bulging outward at a rate faster than seen at any other volcano in Alaska. Those are the classic signs of an inactive volcano awakening.

The new signs of activity are clear enough that the Alaska Volcano Observatory has installed four new seismology stations and ground sensors that can detect deformation if the volcano swells further. The activity is still six miles below the surface; there’s no imminent danger of an eruption. And the rate of inflation has slowed the last six months. The gas bubbling from the ground near the base of the mountain is ambiguous; it’s not clearly magma-generated. But it’s not clearly not, either.

The last known eruption was about 1,150 years ago, based on radiocarbon dating of a a volcanic ash layer near Sitka. The Tlingit people have an oral tradition of the volcano erupting some 800 yers ago. The caldera at the top of Mt. Edgecumbe show little erosion; it’s geologically recent.

The geologic mechanisms that have created Mt. Edgecumbe and the other volcanic structures on Kruzof Island are a little mysterious. Further north, west of Anchorage, the Pacific Plate is being subducted under the North American Plate, creating the chain of volcanoes that extends from Mt. Spurr and Augustine Island on the east to the westerly end of the Aleutians. But around Sitka the Pacific Plate is sliding by the North American Plate, along what’s called a transform fault. Perhaps the recent volcanic activity around Edgecumbe will help explain why the volcano is even there.

There’s no guaranty that Mt. Edgecumbe will erupt, let alone any time soon; far from it. But if it does, WC would bet Porky Bickar would love the irony.