The important thing about science is that it has a built-in mechanism for corrections. It doesn’t always work as well as it should, because scientists are people and resist changing their beliefs. The fact remains that assumptions are always open to challenge.
I was reminded of this in watching a DVD on How the Earth was Made, which I’ll review soon. The point I want to make here is that the DVD presents examples as if the scientists involved were searching for pieces of a puzzle that they knew had missing pieces. More often the major breakthroughs – such as plate tectonics – are made when a gradually increasing number of people realize that the accepted theory just doesn’t explain something. Or many somethings. Essentially, that the puzzle pieces available have been put together wrongly, and the picture is in fact quite different.
This happened with plate tectonics.
I wasn’t involved directly, but I was at the Geophysical Institute when it happened, and had a chance to read many of the papers as they came out. And I was interested enough to do just that.
Even as early as grade school, I was unsatisfied with the encyclopedia’s explanation of mountain-building and geosynclines. What the encyclopedia said was that mountains were formed by the cooling and shrinking of the Earth, much as wrinkles are formed on the skin of a drying apple. Erosion wore the mountains down, depositing the sediments offshore, and the weight of those sediments pushed the ocean crust down so the mountains grew higher. It did not make sense to me, even then. These processes would have resulted in filling the oceans and leveling the mountains, not building them!
When I was a little older – high school age – I was given a book that gave some of the results of the International Geophysical Year – the IGY. The one that stuck in my mind as an unsolved mystery was the discovery of major east-west trending faults in the Pacific Ocean. Based on the offset of newly discovered magnetic stripes, these faults had large displacements – tens to hundreds of miles. But the displacements totally disappeared when the faults reached land! Not only could the east-west displacements not be found, in places such as the California coast there were well-known faults such as the San Andreas tending more nearly north-south.
At Harvard I took a basic geophysics class, hoping it would help me make sense of what seemed to be an increasingly frustrating puzzle. What I learned there – and it was the cutting-edge science of the early 60’s – left me as puzzled as ever.
Gravity measurements had proved that continents stood higher than oceans because continental rock was less dense than ocean rock. This was known as isostacy – the height of terrain essentially depended on how high it floated on the mantle.
Continental drift was nonsense – there was no way continents could plow through oceanic crust, and there were no traces of any such plowing through on the sea floor. The matching of rock formations on the opposite sides of the Atlantic was sheer coincidence.
Exchanges of plants and animals over geological time were via land bridges.
The elephant in the room, from my point of view, was that isostacy did not allow sea floor to rise and form land bridges.
I went to the Geophysical Institute as a graduate student partly because of these mysteries, but I was sidetracked into atmospheric science and ice fog. Nevertheless, I stayed interested, and since many of the seminal papers in plate tectonics were published in the Journal of Geophysical Research (JGR) I watched the plate tectonics revolution happen. Next week I’ll talk about some of the breakthroughs that eventually led to the new paradigm of plate tectonics.