Steens Mountain

The Steens Mountain Conundrum,
from Science Frontiers #80, Mar-Apr 1992.
Copyright 1997 William R. Corliss

The layered lava flows of Steens Mountain, in southeastern Oregon, have preserved video-like records of the earth's magnetic field as it switched from one polarity to another about 15.5 million years ago. The scientific "instruments" here are the cooling lava flows. As they solidify from the outside in, a process taking about 2 weeks for a 2 meter-thick flow, the lava is magnetized in the direction of the field prevailing at the moment of solidification. We would thus have a 2-week continuous record of the behavior of the earth's field. Ordinarily, we would not expect to see very much change in 2 weeks; even a reversing field is thought to take thousands of years to complete its flip-flop. However, at Steens Mountain, when the field reversed 15.5 million years ago, the lava flows suggest that the field's axis was rotating 3-8° per day - incredibly fast according to current thinking, in fact a thousand times faster than expected.

The conundrum (one might call it a scientific impasse) arises because the flowing electrically conducting fluids that supposedly constitute the earth's dynamo would have to flow at speeds of several kilometers/hour. No one has ever contemplated molten rock moving at such speeds in the core!

Could it be that the prevailing dynamo theory is incorrect?

To make matters more interesting, it now seems that the paths taken by the reversing poles follow similar routes with each flip-flop. One preferred path is a band about 60° wide running northsouth through the Americas; the other path is 180° away cutting through east Asia and just west of Australia. The implication is that some unknown structure in the core somehow guides the reversing poles.

Almost Inconceivable Changes in the Geomagnetic Field,
from Science Frontiers #101 Sep-Oct 1995.
Copyright 1997 William R. Corliss

A decade ago, a trio of geophysicists published a group of papers based on their measurements of the remnant magnetism of the 16-million-year-old layered lava flows at Steens Mountain, Oregon. (SF#45) At that time, they claimed that these finely bedded lava flows testified that, during a field reversal, the earth's field swung around at the astonishing rate of 3° per day! This rate is about one thousand times the current rate of polar drift. Mainstream geophysicists could not believe the 3°/day figure because it implied incredibly rapid changes in the flow of those molten materials within the earth that supposedly generate the geomagnetic field. The Steens Mountain data were "tabled"; that is, dismissed.

The three researchers, though, continued their labors at Steens Mountain and have now offered additional, even more impressive data. They now find that the geomagnetic field probably shifted as much as 6° in a single day. Their work has been carried forward so professionally and meticulously that other scientists are finding their conclusions harder and harder to dismiss. Instead, the search is on for explanations of the rapid field changes. Three possibilities have been advanced -- all of them unpalatable to geophysicists:

• The Steens Mountain rocks are not faithful recorders of the main geomagnetic field. Should this be actually so, the whole field of paleomagnetism, including plate tectonics, is undermined, for it depends upon similar measurements.
• The earth's molten core can change rapidly, at least in some regions, in response to forces still unrecognized. This, of course, is not really a satisfying "explanation."
• The dynamo theory of the origin of the geomagnetic field is incorrect.

Coe, R.S., et al; New Evidence for Extraordinarily Rapid Change of the Geomagnetic Field during a Reversal, Nature, 374:687, 1995. Merrill, Ronald T.; Principle of Least Astonishment, Nature, 374:674, 1995. Appenzeller, Tim; A Conundrum at Steens Mountain, Science, 255:31, 1992. Lewin, Roger; Earth's Field Flips Flipping Fast, New Scientist, p. 26, January 25, 1992.