In the world of science there have been a handful of significant moments that have become iconic –
’s apple, Archimedes’ “eureka” bath, Armstrong on the Moon. What about the most earth-moving scientific discovery of the 20th century – continental drift? Why does it not have a defining moment? It’s probably because continental drift has been a series of discoveries made over many years building up the evidence to give the full picture. From the earliest theories to the present day many scientists have contributed to the story. Among the most significant was Allan Cox. Newton
Cox was fortunate in having John Verhoogen as a mentor at the
in the 1950s because Verhoogen was one of the very few scientists who believed in continental drift. Rather than be derided for researching and studying a ridiculous theory both men worked on another shared interest – rock magnetism. This was to provide the best evidence to help prove that continental drift existed. University of California
Lava contains molecules of magnetic elements. The earth’s magnetic field aligns these molecules like little magnets, and when the lava cools they become fixed in position. Over the millennia the earth’s magnetic field has switched – sometimes the magnetic north pole has been at the geographical south pole. The microscopic mini-magnets retain their original north-south polarity in solid rock whenever the switch occurs.
During the 1960s Cox published many scientific papers on the subject. But the problem was how often, and for how long, did the pole reversals last? Imagine you know nothing about the calendar – what you have are 50 random mixed-up pages from a 365-day diary, but you don’t know how many days there are in a week or in which order, and neither for the months also. That was Cox’s challenge – to put data he collected from rocks of all geological ages from around the world into the correct order using the rocks' magnetism to create a time-line. He and his colleagues, Richard Doell and Brent Dalrymple, came up with a theoretical time-line known as the Cox-Doell-Dalrymple Calendar. Then he found his "365-page diary" with most of the data in complete sequence – the mid-Atlantic ocean ridge. Now Allan could see which rock sample matched the magnetism in the complete Atlantic sequence.
As the mid-ocean ridge spreads it produces magnetic molecules in the magma which fix into position as the rock cools, so from
South America to Africa there is a complete continuous record of rock magnetism covering many millions of years. The poles switch, and this is recorded forever in the rock molecules. Measurements of the sea floor revealed a series of strips of magnetic reversal in rocks running down either side of the mid-ocean ridge. On the simplified diagram here it looks like a lot of zebra stripes running down the Atlantic floor. The mid-ocean ridge is the peak in the middle from which the ocean floor spreads outwards. The black and white stripes indicate when the poles switch. If the diagram was animated, and the pole switched again, then a new white stripe would begin to appear at the central ridge. No scientist could doubt continental drift now.
In a way Allan Cox’s geological career began with the study of other slow-moving objects – glaciers. In 1950 he got a summer job with the US Geological Survey as a field assistant to the senior geologist Clyde Wahrhaftig. They were studying glacial activity in
His enthusiasm for outdoor teaching spread into publishing a tour of San Francisco’s geological features using public transport called “Streetcar to Subduction” (Clyde hated fast cars and planes, he never learnt to drive, and wasn’t keen on the over-reliance on fossil fuels). He also wrote a walking geology tour of the city.
The environmental side of his work was used extensively, most prominently in the area of forest management which utilised his studies on the effects of soil erosion and deforestation. In 1971 he became Chair of the Environment and Public Police committee of the Geological Society of America (GSA). He also became the first Chair of the GSA’s Minority Participation in the Earth Sciences committee the same year.
At that time
Clyde was a closeted gay man. His devotion to his career helped get him through the self-doubt and worries that most gay men were going through. For quite a while he and Allan Cox were in a relationship which was kept secret until after Cox’s death. Clyde didn’t come out until he was awarded the GSA’s Distinguished Career Award in 1989. He used his acceptance speech to come out and urge the geological world to accept gay students without bias.
Clyde Wahrhaftig died on the 6th April 1994 of heart failure aged 74. Allan Cox died 7 years before. In 1986 Cox was accused of having improper relations with a teenage boy and was under police investigation. It is possible that Cox decided to take his own life, for there has yet to be a good reason why, on 27th January 1987, he decided to ride his bicycle down a steep road, steer off, and hit a redwood tree. He was 61. The exact circumstances don’t support an accidental death theory.
The legacy of both Allan and
Clyde live on because of their research. Both men provided evidence that effect the way we look at the world today – whether forest management or plate tectonics. Both men were recognised by the scientific world for their contribution to science, and both received many awards for their work during their life time.