Science: Down to Moho

Half in jest, the American Miscellaneous Society (AMSOC) was "founded" by alphabet-weary scientists at the Office of Naval Research in 1952. AMSOC has about 50 members, but no records, dues, laws or officers; its meetings have been held at Washington cocktail parties with a two-member quorum. Typical agenda item: how to tow Antarctic icebergs north and melt them to irrigate Southern California. But in science the impractical can turn practical overnight with a little cash behind it. In Scientific American this week, Geologist Willard Bascom published the first full report of a onetime AMSOC daydream, which is now backed by the National Science Foundation: to drill a hole right down through the earth's crust to its hidden interior.

Imaginative people have mulled the idea for years. Novelist Arthur Conan Doyle, who visualized the earth's shell as a living creature, made his fictional Professor Challenger poke a sharp drill eight miles down, called his story When the World Screamed. AMSOC's goal is to pierce the Mohorovicic discontinuity, which scientists call the Moho for short.

Flexible Finger. The Moho was discovered in 1909 by Seismologist A. Mohorovicic of Yugoslavia, when he noticed that the speed of earthquake waves increases suddenly at a certain level under the earth's surface (the depth varies from place to place). This suggested that the Moho marked a dividing line between different materials. Geologists believe that the Moho is the bottom edge of the granite and basalt that forms the lower layer of the earth's crust; under it is the earth's mantle consisting of a mixture of silicates and nickel-iron, which in turn encloses the nickel-iron core.

The drilling cannot be done on the continents because they are great rafts of granite "floating" in deeper plastic material. The granite is too thick (20 miles) to drill through. Oceanic islands are also ruled out as drilling sites; their weight has pressed the Moho to an impossible depth. The best place to drill is the floor of the great ocean basins. The floor may be three miles beneath the ocean's surface, but the Moho lies only three or four miles deeper, under a thin skin of sedimentary deposits and a layer of basalt.

The job would have been unthinkable a few years ago. But the new search for offshore oil has developed machinery capable of doing it. The rig that appeals to AMSOC is the Cuss I (named for Continental, Union, Shell and Superior companies), a 3,000-ton barge with a 98-ft. drilling derrick mounted amidships. The drill is carried on gimbals, so that heavy seas will not snap the drill pipe.

First step toward the Moho would be to drill a cone-shaped hole in the sea bottom. The hole would be filled with cement poured down the drill stem and a steel platform fixed in the cement. The rock drill would be passed through this steel collar and turned from the barge. The long drill stem would be flexible enough to allow for the ship's motions.

Primordial Face. Cuss I has already drilled sample wells off California in water 1,500 ft. deep. Drilling in three miles of water would be harder, but Geologist Bascom thinks it can be done. So do the Russians, who claim to have drilling equipment just as good, and are apparently trying to beat AMSOC to the Moho.