No. 98: Mar-Apr 1995
It takes a lot of nerve to propose a theory that can unite such a fragmented field as geophysics. H.R. Shaw makes a try in his new book: Craters, Cosmos, and Chronicles: A New Theory of the Earth. Shaw's ideas have recently been reviewed in Science News and our item is based on that article.
Shaw contends that cosmic projectiles -- asteroids and comets -- have controlled almost all features of the earth's evolution. For example:
Of course, for two centuries, other catastrophists have proposed similar dire consequences of giant impacts. But Shaw does introduce three ideas that are worth recording here.
Large impact craters occur in swaths. Although this has been suggested before, Shaw has mapped out several swaths where large craters of about the same age are located. His "K-T swath" includes the Chicxulub crater (Yucatan), the Manson crater (Iowa), the Avak crater (Alaska), and three more in Russia -- all of which were gouged out about the time of the Cretaceous-Tertiary (K-T) boundary. Shaw has plotted several other swaths of different ages.
The application of chaos theory to solar system debris. Shaw hypothesizes that nonlinear gravitational effects channel asteroids and comets into the inner solar system in intermittent bursts. The bursts are then captured by the earth and other inner planets, with some of these objects grouped in like orbits.
Gravitational feedback occurs from earth to orbiting debris. Shaw believes that the uneven distribution of mass inside the earth -- due probably to the impact that created the moon -- influences where asteroids and comets impact. In turn, these large objects keep smashing into the same regions and their cumulative effect contols the flow of material inside the earth. Then, this change in mass distribution feeds back to change orbits and impact swaths.
The above is just a taste of what is revealed in Shaw's book of 600+ pages. It cannot fail to be controversial.
(Monastersky, Richard; "Shots from Outer Space," Science News, 147:58, 1995.)