Chilean Earthquake Highlights Darwin Error

Torres Del Paine

An 8.8 magnitude earthquake

By Brian Thomas

On February 27, Chile experienced an 8.8 magnitude earthquake, the fifth-largest recorded quake since seismographs were implemented. Charles Darwin experienced a similar quake in the same area on February 20, 1835. The conclusions he drew then provide an interesting contrast to what is now known about earth’s geologic activity.

The epicenter of Chile’s devastating February 27th earthquake was 62 miles north of the city of Concepcion and was the second strongest in Chile’s recent history. The largest recorded temblor was an estimated magnitude 9.5 in 1960 that occurred 143 miles north of the recent quake, although geologic faults around the world indicate that some past earthquakes absolutely dwarfed these modern ones.

The magnitude 8.5 earthquake Charles Darwin experienced while aboard the HMS Beagle struck Concepcion and devastated the inhabitants. At the time, he was making careful notes at each stop on his long voyage. He noticed that a nearby island was uplifted as a result of the quake and was able to measure the distance from sea level to the top of the old water line.

Darwin interpreted this as confirmation of a long-age view of mountain-building that has since been shown to be false. Historian Sandra Herbert wrote in her 2005 book Charles Darwin, Geologist, “In Darwin’s view, a mountain chain, with its axis of plutonic rock, is the effect of ‘an almost infinite series of small movements.’” And those movements were earthquakes.

But whereas Darwin thought of vertical pressure pushing up mountains from below, today it is known that the island was uplifted in 1835 by horizontal pressure from offshore. Earthquakes are not known to lift continents or mountains. The recent quake moved Concepcion ten feet westward, with surrounding areas traveling shorter distances in the same direction. This tendency flattens South America instead of raising it…

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image credit: Artwork of Torres Del Paine from original photo