EDITORIAL PAGE — The bear facts of geophysics

My first summer job in geophysics was as a horizontal loop electromagnetic (EM) transmitter operator in the Yukon in 1966. The Anvil camp had recently been discovered by Dr. Arro Aho, and an intense exploration effort was under way in the Ross River area to find similar lead-zinc mineralization. There were many remote, helicopter-supported tent camps in the area carrying out geochemical and geophysical exploration.

The geophysical instrument of choice in those days was a Ronka Mark IV horizontal loop EM system, which consisted of two large, 40-inch coils of wire separated by 200 ft. of cable. The transmitter operator led the way down the line, with one of these horizontal “hula hoops” suspended from his shoulders. The receiver operator followed 200 ft. behind, with a similar hula hoop suspended from his shoulders, making measurements of the mutual impedance between the two coils. A conductor (and possible lead-zinc deposit) was indicated when the mutual impedance changed.

Unbeknowst to the crew, this area of the Yukon had been host to a large population of grizzly bears, who took a dim view of man’s incursion into their domain. We heard from our helicopter pilot of an exciting encounter between one such beast and a horizontal loop EM team in a nearby Kerr-Addison camp. The encounter ended with the EM operators racing down the line, shedding battery packs and hula hoops over their heads as they dashed for a tree.

Things were really touch-and-go for the receiver operator, who, being last, was desperately trying to outrun an angry grizzly bear hot on his tracks. Fortunately, the bear stepped on one edge of the discarded hula hoop, causing the other side to swing up and hit him on the nose. The operator managed to climb up the tree, while the bear stopped to beat the heck out of the offending receiving coil.

Later, a very shaken EM crew came down out of the tree to pick up their equipment and head back to camp.

Twelve years later, I spent three months in India with Finnish geophysicist Vaino Ronka on a United Nations development program organized by Norm Paterson, and which included Gordon West (University of Toronto) and Adam Osborne (Osborne Computers). Vaino was pleased to find out that his equipment ended up being effective grizzly protection.

— Bill Pelton is a geophysicist in Denver, Colo.