Charles Darwin was wrong Today, February 12th, is the 205th birthday of one of history’s most

Charles Darwin was wrong Today, February 12th, is the 205th birthday of one of history’s most famous scientists, Charles Darwin, celebrated throughout the world as Darwin Day. Although Charles Darwin is best known for developing the theory of evolution by natural selection, that story is not his only contribution to science. These boulders relate to a different part of Darwin’s voyage on the HMS Beagle; the trip which took him to the Galapagos and drove development of his most famous theory. These boulders are a story Charles Darwin got wrong. I think of myself as a geoscientist. In that sense, I might be able to talk in depth about many topics throughout Earth Science, but my field is still specialized. The kind of common today is fundamentally different from the kind of science done by Darwin, who would have considered himself a “naturalist”; a scientist devoted to the natural world. While on the Beagle, Darwin wasn’t just interested in the biology; he was interested in whatever he saw, including the rocks. These rocks dot the shores near Bahía San Sebastian, south of the Straits of Magellan in Tierra del Fuego. When Charles Darwin saw these rocks, they reminded him of the writings of Dr. Charles Lyell, which described enormous blocks found on the ocean floor off the coasts of Newfoundland. Those rocks arrived via icebergs; floated across hundreds of kilometers of oceans. This process, boulders being carried by icebergs, had even been observed by ships; reports of which Darwin referred to in his writings. Darwin studied the rocks of Tierra del Fuego and realized that far above the shorelines, the rocks contained oceanic fossils. With this fact in hand, he surmised that some geologic forces had lifted the fossils far above the modern day beach. And, since fossils from the ocean could be lifted to great heights, Darwin also surmised that these boulders were dropped on the ocean floor, carried originally by icebergs from Antarctica, and brought up to the surface by later geologic uplift. Boulders like this, erratically strewn throughout the known world, were common and well-known. This process was Darwin’s explanation for their origin. Several years ago, a group led by Dr. Evenson from Lehigh University investigated these exact rocks, matching their shape to those described by Darwin in his writings. You are looking at some of the exact rocks examined by Charles Darwin nearly 2 centuries ago. If the rocks were emplaced as Darwin described, they should be unrelated to the rocks on Tierra del Fuego; they should derive from Antarctica. They should also be unrelated to each other – each iceberg would pluck boulders from a different location on Antarctica. The scientists tested the chemistry of the rocks and noted their geologic context. The boulders in this site are all of a similar composition, identical to a unit found higher up in the nearby mountains (now known as the Beagle granite). There are dozens of boulders at this site, all derived from the same unit. By studying the surrounding geology, the scientists realized that they were standing on a terminal moraine – the place where a prehistoric glacier, born in the mountains above, had ended. By putting together the geologic history…they came to realize…Charles Darwin was wrong. Although Darwin’s observations were interesting, he did not understand one detail at the time. It had yet to be recognized that, over the last several million years, ice sheets had repeatedly formed on the continents and expanded far out of the mountains. Charles Darwin understood the power of ice, but did not recognize that at one time, enormous ice rivers had migrated down from the mountains in Tierra del Fuego, carrying these rocks with them. The kind of data available to us today allows us to tell the story of these rocks in far more detail than could be done in Darwin’s time, but in many ways, this story gives an interesting look into the type of science and thought done by the man at the time. In 1833, Charles Darwin delayed the voyage of the ship to stop and describe a few large chunks of rock found on the shores of a nearly-deserted part of the world, to try to tell their story. As a result, today we can tell the story both of these rocks and of the voyage of the Beagle as well. -JBB Image credit: Henry Patton (creative commons license)http://www.flickr.com/photos/hpatton/3717733679/ Full article:http://www.geosociety.org/gsatoday/archive/19/12/article/i1052-5173-19-12-4.htm -- source link

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