Glacial Climate Cycles
The discovery of the glacial cycles was a slick piece of detective work. Earth scientists two centuries ago were not professionals in the modern sense. They were not motivated by publishor–perish rules at universities, or competition for research grant money. Many were gentlemen of privilege, or quirky devoted amateurs, with the determination to indulge a passion of choice, in this case an interest in the history of the Earth.
Here’s the case. The mountains in Switzerland are scattered with rocks called exotics, large rocks that once broke off from bedrock hundreds of kilometers away. The question is, how did the natural world move so many big rocks such long distances?
The default hypothesis was of course the great flood described in the Bible. But when you get down to actually imagining these rocks being carried in a great flood, it’s not so easy to do, especially for the larger ones. When it does happen that rocks are carried along in some torrential water flow, the rocks get all rounded from tumbling, and they wind up in beds well sorted by size. The Swiss rocks in question are angular and rough, definitely not rounded.
The rocks in the Swiss mountains have another distinctive feature. Their flat surfaces are scored with long, straight, parallel scratches, or smoothly polished parallel grooves. Mountain gla-