Charles Darwin – Geologist

Darwin, four years after the "Beagle's" return.  Source

Darwin, four years after the “Beagle’s” return. Source

Today, most of us think of Darwin in terms of evolution (this actually came much later in his career) and perhaps also the Galapagos Islands. However, much of his description of the Beagle’s almost five-year trip around the world is about geology.

This is only fitting for a book whose full title is Journal of Researches Into the Natural History and Geology of the Countries Visited During the Voyage of H.M.S. Beagle Round the World
 

Watercolor of the Beagle by her draughtsman, Conrad Martens.  Source

Watercolor of the Beagle by her draughtsman, Conrad Martens. Source


The voyage of the Beagle

Charles Darwin was in his early 20s during the trip (the second of a series of three Beagle expeditions).

He got the position because the ship’s captain, who was just four years older, was looking for a gentleman/naturalist as a companion over the long voyage. (At various times during the journey, surgeons Robert McCormick and then Benjamin Bynoe played Bones to Captain Fitz Roy and Darwin’s Kirk and Spock).

Darwin, from a wealthy family, was most definitely a gentleman. His interest in natural science was of long standing, though he had attended the University of Edinburgh to study medicine and then switched to Cambridge University for theology.

He later would say that two books that greatly influenced him were John Herschel’s Preliminary Discourse on the Study of Natural Philosophy and Alexander von Humboldt’s Personal Narrative of Travels to the Equinoctial Regions of the New Continent.

His mentor at Cambridge, John Henslow, had helped along the youth’s interest in geology. Darwin actually came to the Beagle directly from a field trip in North Wales with geology professor Adam Sedgwick, who taught him to observe, make geologic maps, and collect specimens.

Charles Darwin was ready to go and had the ideal voyage waiting for him!
 

For reading material, Darwin set sail with volume one of Charles Lyell‘s Principles of Geology. He picked up volume two during the trip.

Lyell’s influence is seen in some of Darwin’s comments:

Along the whole coast of Brazil, for a length of at least 2000 miles, and certainly for a considerable space inland, wherever solid rock occurs, it belongs to a granitic formation. The circumstance of this enormous area being constituted of materials which most geologists believe to have been crystallized when heated under pressure, gives rise to many curious reflections. Was this effect produced beneath the depths of a profound ocean or did a covering of strata formerly extend over it, which has since been removed? Can we believe that any power, acting for a time short of infinity, could have denuded the granite over so many thousand square leagues?

 

Granite formations around the coastal city of Rio de Janeiro.  Mario Roberto Durán Ortiz

Granite formations around the coastal city of Rio de Janeiro. Mario Roberto Durán Ortiz

Geology from A to Z

Here are just a few of the geologic-related entries in the index to Voyage of the Beagle (X and Y have no entries at all):

  • Aconcagua, volcanoes of
  • Basaltic platform of Santa Cruz
  • Chalk-like mud.
  • Degradation of tertiary formations.
  • Erratic blocks, how transported
  • Fulgurites
  • Granite mountains: Tres Montes; of Cordillera [the Andes]
  • Hill, emitting a noise.
  • Islands, oceanic, volcanic: Antarctic; floating; low
  • Jajuel, mines of
  • Kater’s Peak
  • Lyell, Mr.: on terraces of Coquimbo; on longevity of Mollusca; on subsidence in the Pacific; on change in vegetation; on fossil horses’ teeth; on distribution of animals; on frozen snow; on extinct mammals and ice-period; on flocks of butterflies; on stones twisted by earthquakes
  • Maldive atolls
  • New Caledonia, reef of
  • Ores, gold
  • Patagonia, geology of
  • Quartz of the Ventana; of Tapalguen; of Falkland Island
  • Rocks burnished with ferruginous matter
  • Sandstone of New South Wales
  • Terraces in valleys of Cordillera; Coquimbo; of Patagonia
  • Uspallata range and pass
  • Valley of St. Cruz, how excavated; dry, at Copiapo. Valleys, excavation of; in Chile; of Tahiti; in Cordillera; of New South Wales.
  • Waves caused by fall of ice; from earthquakes
  • Yeso, Valle del

 

The 1835 Valdivia earthquake

Charles Darwin observed erupting volcanoes, glacial deposits, coral atolls, and rock stratigraphy, among other things, but his account of the M8.2 earthquake in Valdivia, Chile, demonstrates his unique ability to make detailed observations, convey his experiences vividly, and make deductions.

When it struck on February 20, 1835, he and the crew were on land, near a fort called Niebla. In addition to a reworked version of that linked diary entry, Darwin later wrote in Voyage [image added]:

March 4th. – We entered the harbour of Concepcion. While the ship was beating up to the anchorage, I landed on the island of Quiriquina. The mayor-domo of the estate quickly rode down to tell me the terrible news of the great earthquake of the 20th: – “That not a house in Concepcion or Talcahuano (the port) was standing; that seventy villages were destroyed; and that a great wave had also washed away the ruins of Talcahuano” Of this latter statement I soon saw abundant proofs – the whole coast being strewed over with timber and furniture as if a thousand ships had been wrecked…

The island itself as plainly showed the overwhelming power of the earthquake, as the beach did that of the consequent great wave. The ground in many parts was fissured in north and south lines, perhaps caused by the yielding of the parallel and steep sides of this narrow island. Some of the fissures near the cliffs were a yard wide. Many enormous masses had already fallen on the beach; and the inhabitants thought that when the rains commenced far greater slips would happen. The effect of the vibration on the hard primary slate, which composes the foundation of the island, was still more curious: the superficial parts of some narrow ridges were as completely shivered as if they had been blasted by gun-powder. This effect, which was rendered conspicuous by the fresh fractures and displaced soil, must be confined to near the surface, for otherwise there would not exist a block of solid rock throughout Chile…

After viewing Concepcion, I cannot understand how the greater number of inhabitants escaped unhurt…
 

Remains of the cathedral at Concepcion.  Source

Remains of the cathedral at Concepcion after the 1835 earthquake. Source



Shortly after the shock, a great wave was seen from the distance of three or four miles, approaching in the middle of the bay with a smooth outline; but along the shore it tore up cottages and trees, as it swept onwards with irresistible force. At the head of the bay it broke in a fearful line of white breakers, which rushed up to a height of 23 vertical feet above the highest spring tides…The first wave was followed by two others, which in their retreated carried away a vast wreck of floating objects…

In almost every severe earthquake, the neighbouring waters of the sea are said to have been greatly agitated…During most earthquakes, and especially during those on the west coast of America, it is certain that the first great movement of the waters has been a retirement. Some authors have attempted to explain this, by supposing that the water retains its level, whilst the land oscillates upwards; but surely the water close to the land, even on a rather steep coast, would partake of the motion of the bottom: moreover, as urged by Mr. Lyell, similar movements of the sea have occurred at islands far distant from the chief line of disturbance. I suspect (but the subject is a very obscure one) that a wave, however, produced, first draws the water from the shore, on which it is advancing to break…It is remarkable that whilst Talcahuano and Callao (near Lima), both situated at the head of large shallow bays, have suffered during every severe earthquake from great waves, Valparaiso, seated close to the edge of profoundly deep water, has never been overwhelmed, though so often shaken by the severest shocks…I suspect we must look to the line, where the less disturbed waters of the deep ocean join the water nearer the coast…as the place where the great wave is first generated; it would also appear that the wave is larger or smaller, according to the extent of shoal water which has been agitated together with the bottom on which it rested.

In focusing on water depth, Darwin was close to the correct explanation of tsunamis.

Of course, a picture is worth a thousand words. Here is what the tsunami looked at Valdivia after an even more powerful earthquake (M9.5) struck in 1960:
 

A personal note

I’m especially impressed with Charles Darwin’s “geologising” during the Beagle voyage because of my experiences as a geology undergrad in the 1980s.

In an introductory course, our SUNY professor took us to a nearby park, unloaded us at the top of a steep hill that had boulder outcrops and low limestone cliffs, gave us measuring rods and told us to get down there and map the hill.

Up until then we had been having a lark on a nice fall Saturday morning, but things got real quickly due to the high angle of the slope and the professor’s reputation as a stickler. We didn’t dare goof off, though there was plenty of grumbling.

After a while, though, it got to be fun, looking for the different layers in outcrops and matching them to what showed in the cliffs. I don’t have any pictures of it, unfortunately. It was all I could do to keep my balance and catch my breath (though it wasn’t really a dangerous spot, it certainly demanded your attention).

We started out down at the bottom as a disorganized group of students, but by the time we reached the top, some of us had become budding geologists.

Later that afternoon, I noticed a stone elsewhere in the park and for the first time ever saw it as a book that recorded life (now fossilized) in a shallow sea somewhere, with its fine sediment during quiet times and upturned layers of mud and shell during violent events (storms or mudslides).

Though I didn’t become a geologist, I still view rocks more as books in a vast library than as scenery.
 

morguefile/PMaz

morguefile/PMaz

It’s so awesome that Charles Darwin had an opportunity to undergo something similar but far greater in scope and value. For him, the Earth was a great book whose chapters were written gently over a long time, not in a sudden dash of catastrophic capital letters.

Given that record of deep geologic time, he then productively thought about all he had seen, experienced and collected during the voyage of the Beagle. In doing so, Charles Darwin came up with, among other things, the theory of evolution, changing humanity’s view of the itself and the world forever.

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