How Charles Darwin Classified His Minerals And Rocks

In an autobiographic note Charles Darwin remembers a childhood wish:

“It was soon after I began collecting stones, i.e., when 9 or 10, that I distinctly recollect the desire I had of being able to know something about every pebble in front of the hall door–it was my earliest and only geological aspiration at that time.“

Also during later school years Darwin remains interested in chemistry and minerals, however he laments that “I continued to collecting minerals with much zeal, but quite unscientifically – all that I cared was a new named mineral, and I hardly attempted to classify them.” As a medicine student at Edinburgh University (1825-1827) Darwin frequented various courses on natural sciences, also lectured by mineralogist Professor Robert Jameson, however he considered Jameson´s lectures as „incredibly dull“. Nevertheless Darwin seems to have used frequently Jameson´s „Manual of Mineralogy“ for his private studies, as it is one of the most heavily annotated books in his library. Jameson´s manual uses physical properies, like color and especially the degree of hardness, introduced by German mineralogist Carl Friedrich Christian Mohs in 1822-1824, for mineral identification. Darwin adopts this “visual characterization” approach, so he often describes rocks based on the well visible physical properties, referring to mineral texture or colors, using terms like “porphyry”, for rocks with large, well visible, crystals, "greystone" or “greenstone”, a general name for greenish-dark magmatic rocks (today classified as dolerite-basalt).

In summer of 1831 Darwin joined a field trip of professor Adam Sedgwick, geologizing in Wales. Darwin was interested in acquiring the basics of geological field work, structural geology and rock classification. Twenty pages of notes made by Darwin during this tour are still today preserved – in his autobiography he will later remember: “This tour was of decided use in teaching me a little how to make out the geology of a country...”

When Darwin returned to Shrewsbury, August 29th, a letter from Captain Robert FitzRoy was offering him a position as gentlemen companion on board of the brig Beagle, ready to set sail from Plymouth in December 1831. 

Darwin used the remaining time to exercise mineral identification with the blowpipe (heating a mineral you then observe the chemical redactions and modifications of the specimen to identify it or its composing elements) and muriatic (hydrochloric) acid, useful to distinguish between carbonatic and siliceous rocks

On board of the Beagle Darwin could rely on a complete library for mineral identification, like "A selection of the Geological Memoirs" (1824), including a mineral chart by French geologist A. Brongniart. These manuals use properties like color, hardness, form, but also taste and odour for mineral identification. Darwin got for himself a goniometer, to measure angles of crystal-faces, a not easy to use tool in the field but Darwin proudly remarks "Hornblende determined by myself with goniometer".
Especially interesting are classification charts based on the color of a specimen. "Werner's nomenclature of colors”, published in 1821 by Patrick Syme (1774-1845), is a book displaying a chart and description of various colors to be compared with the colors of minerals, animals and plants. Darwin used this book to describe snakes, rocks and even the "beryl blue" glaciers.

Fig.1. Page from "Werner's nomenclature of colors”, the book was brought on board of the Beagle by Darwin himself.

It is curious to note that Darwin not only used a mineral classification scheme based on the work of German mineralogist Mohs. He adopted also the geological terms used mostly by German geologists, like Alexander von Humboldt, to describe the rocks observed in the field. Darwin will become especially interested in volcanic rocks.

Darwin´s final advice published in 1839 for collecting rocks has value still today (even if Darwin himself admitted he didn´t follow it always):

"Put a number on every specimen, and every fragment of a specimen; and during the very same minute let it be entered in the catalogue, so that if hereafter its locality be doubted, the collector may say in good truth, “Every specimen of mine was ticketed on the spot." Any thing which is folded up in paper, or put into a separate box, ought to have a number on the outside (with the exception perhaps of geological specimens), but more especially a duplicate number on the inside attached to the specimen itself."

Fig.2. Page with rock-classification from Jameson 1821 (influenced strongly by the work of German geologists), Darwin will himself adopt "German" terms like "Amygdaloid" to describe basaltic lava flows observed on the volcanic islands visited during the voyage of the Beagle.

Bibliography:

HERBERT, S. (2005): Charles Darwin, Geologist. Cornell University Press: 485
ROBERTS, M. (2001): Just before the Beagle: Charles Darwin’s geological fieldwork in Wales, summer 1831. Endeavour Vol. 25(1): 33-37

The true treasure of the North

GOLD! GOLD! GOLD! found in the Klondike river in the Yukon territory, Alaska. The news spread like wildfire, fueling the last great gold-rush of the United States in 1896-99.
 

Fig.1." The Prisoner of White Agony Creek" (2008).

Also French businessman Loicq de Lobel decided in 1898 to try his luck in the new world. Even if not directly interested in searching for gold, he hoped to make a living by selling equipment to the prospectors. So the family de Lobel, his wife and four children, following the famous Chilkoot Trail ventured into the northern wilderness, first by feet and later by boat. To distract herself from the perils of the voyage, de Loicq´s wife, which name is not recorded, botanized along the way. She collected for the very first time specimens of the endemic lady's-slipper orchid, Astralagus, bearberry, Epilobium, arnica and a blue-flowering bellflower.

 “… everywhere there were nice flowers, at our arrival at Glenora we found lots of flowering plants...”
 

The de Lobel family lived for a time in the Yukon territory, then moved to the Aleuten Islands, to finally return to France. The Klondike Gold Rush ended as suddenly as it began, only few found great riches and fortune. However the collected plants by the de Lobel became known as “Klondike River Herbarium” and represents still today a unique botanic treasure.

Bibliography:

THINARD, F. (2013): Das Herbarium der Entdecker - Humboldt, Darwin & Co. - botanische Forscher und ihre Reisen. Haupt-Verlag: 168

The Geology of the Mountains of Madness

“[]…we expected to unearth a quite unprecedented amount of material – especially in the pre-Cambrian strata of which so narrow a range of antarctic specimens had previously been secured. We wished also to obtain as great as possible a variety of the upper fossiliferous rocks, since the primal life history of this bleak realm of ice and death is of the highest importance to our knowledge of the earth’s past.“

100 years ago only segments of the coast and the approximately contours of Antarctica were known – a perfect scenario to be filled by the imagination of a writer. In 1888 the novel “A Strange Manuscript Found in a Copper Cylinder“, by Canadian James De Mille, was posthumously published (Brian Switek recovers these lost tales on his Dinosaur Tracking post “Who Wrote the First Dinosaur Novel?“). The novel narrates the adventures of a sailor shipwrecked on an unknown part of the continent, where volcanic activity enables a tropical lost world to flourish. Only in 1912, maybe also in response to the successful expeditions to the South Pole, Arthur Conan Doyle reinvented “The Lost World” in a remote region of the Amazonian forest. Curiously Edgar Rice Burroughs published in 1918 the first part of “The Land That Time Forgot“, maybe hoping to exploit the celebrity of Doyle’s tale. Here the primordial world populated by tropical forests and of course dinosaurs is located again near Antarctica on the island of Caprona, first reported by the (fictitious) Italian explorer Caproni in 1721.

“At the Mountains of Madness” is a science-fiction/horror story by the American writer H. P. Lovecraft (1890-1937), written in February/March 1931 and originally published in the February, March and April 1936 issues of one of the first pulp-magazine of history: “Astounding Stories“.
Like many others stories by Lovecraft also Mountains of Madness is retold from a first-person perspective: Geologist William Dyer is one of the few survivors of an Antarctica expedition that in 1930 studied the geology of the frozen continent. After discovering strange trace fossils a team ventures into the unknown interior of Antarctica, only to discover a terrifying chain of dark peaks:

“He was strangely convinced that the marking was the print of some bulky, unknown, and radically unclassifiable organism of considerably advanced evolution, notwithstanding that the rock which bore it was of so vastly ancient a date – Cambrian if not actually pre-Cambrian – as to preclude the probable existence not only of all highly evolved life, but of any life at all above the unicellular or at most the trilobite stage. These fragments, with their odd marking, must have been five hundred million to a thousand million years old.“

Lovecraft is today considered one of the first authors to mix elements of the classic gothic horror stories, mostly characterized by supernatural beings, with elements of modern science-fiction, were the threat to the protagonists results from natural enemies, life, but not as we know it. He was an enthusiastic autodidact in science and incorporates in his story many geologic observations made at the time, he even cites repeatedly the geological results of the 1928-30 expedition by explorer Richard Evelyn Byrd. Only in 1929-31 the British-Australian-New Zealand Antarctic Research Expedition was mapping the last unknown coastlines and still not much was known about the geology and palaeontology of the interior of the continent.

The first fossils, fragments of petrified wood, described from Antarctica were collected in 1892-93 on Seymour Island by members of the Norwegian Antarctic Expedition led by Carl Anton Larsen (most fossils were traded later by the sailors for tobacco, Larsen handled his specimens to the University of Oslo). One of the first geologists to collect fossils in Antarctica was the Swedish geologist Otto Nordenskjöld in 1902-03, he and his crew discovered Jurassic plant fossils, shells and the bones of gigantic penguins (which also have an cameo in Lovecraft’s tale). Based on the plant fossils Nordenskjöld was also one of the first researchers to propose that Antarctica in the past experienced a much warmer climate and was covered by forests of ferns and other tropical plants. Lovecraft will evocate this long lost past in his story by the unexpected discovery of a cave that acted as sediment trap for millions of years:

“The hollowed layer was not more than seven or eight feet deep but extended off indefinitely in all directions and had a fresh, slightly moving air which suggested its membership in an extensive subterranean system. Its roof and floor were abundantly equipped with large stalactites and stalagmites, some of which met in columnar form: but important above all else was the vast deposit of shells and bones, which in places nearly choked the passage. Washed down from unknown jungles of Mesozoic tree ferns and fungi, and forests of Tertiary cycads, fan palms, and primitive angiosperms, this osseous medley contained representatives of more Cretaceous, Eocene, and other animal species than the greatest paleontologist could have counted or classified in a year. Mollusks, crustacean armor, fishes, amphibians, reptiles, birds, and early mammals – great and small, known and unknown. No wonder Gedney ran back to the camp shouting, and no wonder everyone else dropped work and rushed headlong through the biting cold to where the tall derrick marked a new-found gateway to secrets of inner earth and vanished aeons.“

In 1920 the geologist William Thomas Gordon described the oldest Antarctic fossils, archaeocyathids found in rocks dated to the Cambrian Period (more than 500 million years ago). Archaeocyathids, sponge-like organisms, were also discovered in samples coming from a moraine of Beardmore Glacier and collected in 1907-09 by Ernest Shackleton during his failed attempt to reach the South Pole.
 

The desire to understand the ancient history of Antarctica had also a tragic consequence. December 14, 1911 Roald Amundsen and his team had reached the South Pole, four weeks later Robert Falcon Scott and his team sighted the tent with the Norwegian flag. This unexpected discovery demoralized Scott and his men who had also to face the impending polar winter and an insufficient stock of supplies. However Scott decided during his return to stop at a moraine and collected rock samples, loosing precious time and adding ulterior weight on the sleigh pulled by the men.

“The moraine was obviously so interesting that when we had advanced some miles and got out of the wind, I decided to camp and spend the rest of the day geologizing. It has been extremely interesting . . . Altogether we had a most interesting afternoon, but the sun has just reached us, a little obscured by night haze.“

The samples were discovered in 1912 along with the frozen bodies of the men. In 1914 British palaeontologist Albert Charles Seward described the fossil plant remains collected by Scott’s party as Glossopteris and Vertebraria, two species of plants distributed almost worldwide that will later be used by Alfred Wegener as evidence that Antarctica was once connected to the other continents.

Lovecraft apparently was fascinated by the theory of continental drift as proposed by Wegener in the 1920s, as he describes the discovery of an ancient topographic map of unknown origin in a dead city, showing the slow movement of the continents on the surface of earth.

“As I have said, the hypothesis of Taylor, Wegener, and Joly that all continents are fragments of an original Antarctic land mass which cracked from centrifugal force and drifted apart over a technically viscous lower surface- an hypothesis suggested by such things as the complementary outlines of Africa and South America, and the way the great mountain chains are rolled and shoved up-receives striking support from this uncanny source.“

For Lovecraft the geology and the detailed description of the discovered fossils is an essential part to present the idea of deep time, especially the pre-Cambrian, when according to the knowledge of his time no life existed on earth. However the expedition of Dyer discovers in rocks dated to this ancient period the traces of highly evolved creatures, referred only as the Elder Ones. They are far superior in their culture, technology and abilities to our civilization, most important they are immeasurable older than humans and Lovecraft’s tale ends with a warning: compared to the almost unimaginably vastness of the age of earth (and these creatures) we should feel quite humble (and afraid).

“I am forced into speech because men of science have refused to follow my advice without knowing why. It is altogether against my will that I tell my reasons for opposing this contemplated invasion of the antarctic – with its vast fossil hunt and its wholesale boring and melting of the ancient ice caps. And I am the more reluctant because my warning may be in vain.“

 

Fig.2. Digital Elevation Model of the bedrock of the Antarctic continent, after data from LYTHE, M.B., VAUGHAN, D.G. and the BEDMAP Consortium (2000): A new ice thickness and subglacial topographic model of the Antarctic.

Today much more is known about the geology of Antarctica.  The landmass of Antarctica is composed by two large blocks separated by the Transantarctic Mountains, a 2.800km long mountain range with 4.000m high peaks (Lovecraft´s imaginary Mountains of Madness were more than twice as high as these mountains).

East Antarctica is dominated by Precambrian igneous and metamorphic rocks, however almost completely covered by a 4.000m thick ice cap. Even if East Antarctica is thought to be an ancient and stable continental shield, geophysical investigations showed prominent mountains buried under the ice, like the Gamburtsev Mountain Range, a 1000km long mountain range with peaks almost 3.000m high. The origin of these mountains was for a long time an intriguing mystery – volcanic origin, mountains formed by subduction very recently or the remains of an ancient Gondwanan-orogeny were the most popular hypotheses. Most recent research (FERRACCIOLI et al. 2011) proposes that these mountains are much elder ones, formed by movements during the collision of the various blocks.

West Antarctica is a mosaic of five smaller blocks covered by the West Antarctic Ice Sheet; however rocks are exposed on the Antarctic Peninsula. The Antarctic Peninsula was formed by uplift and metamorphism of sea-bed sediments during the late Paleozoic and the early Mesozoic, as proved by the fossils that inspired Lovecraft.

Bibliography:

HUNTFORD, R. (2010): Race for the South Pole – The Expedition Diaries of Scott and Amundsen. Continuum International Publishing Group: 330
LONG, J. (2003): Mountains of Madness – A Scientist’s Odyssey in Antarctica. Jospeh Henry Press, Washington: 252

The Geology of Star Trek: II. It is not Life as we know or understand it!

It may surprise that there is no exact definition of what “life” is -  it is often described as a system in thermodynamic disequilibrium with it´s own environment and therefore forced to actively seek, incorporate and transform matter and energy. Part of the acquired energy and matter is used by this system to create copies of itself and so to survive it´s own death.

Some of these properties are however shared also by inorganic entities, like the order, growth or twinning of crystals, and a virus can´t grow or replicate without infecting a living cell.
 

"It is not life as we know or understand it!", Mister Spock in the episode „Operation Annihilate” and still from the episode “The Devil in the Dark”

Living bacteria were found in boreholes in 5.278 m depth, on the bottom of oceans, acid and toxic lakes, in hot springs with temperatures of 115°C and in rocks of Antarctica, thriving at -50°C.  Part of this success is explained by the molecular structure of these life forms, as carbon-based molecules are stable in a wide range of temperatures and in acid or basic solutions. 

Mister Spock is well aware of this fact:
 

“Life as we know it, is universally based on some combination of carbon compounds.”
 

However when the crew of the Enterprise is contacted in the episode “The Devil in the Dark” by the miners on Janus VI, supposedly attacked by an unstoppable “monster”, soon this fact is questioned. The creature can´t be tracked by the sensors of the Enterprise, nor by the tricorder and seems immune to direct hits with the phasers.
 

“But what if life exists, based on other element. For instance silicon.”
 

McCoy disagrees with Spock´s deduction, noting that it is a physiological impossibility, however Kirk agrees as it may improbable, but not impossible. Already in 1891 the German astrophysicist Julius Schreiner argued that silicon (Si) could replace carbon in molecules supporting complex chemical reactions and therefore a hypothetical metabolism. Three years later science-fiction author H.G. Wells speculated in an article of popular science about such life forms:
 

“One is startled towards fantastic imaginings by such a suggestion: visions of silicon - aluminium organisms – why not silicon-aluminium men at once? – wandering through an atmosphere of gaseous sulphur, let us say, by the shores of a sea of liquid iron some thousand degrees or so above the temperature of a blast furnace.”
 

In theory, silicon could form polymers and complex compounds together with metals or elements like boron, nitrogen, phosphorus and sulfur (in fact almost all known minerals involve silicon). Such molecules could work also in other liquids than water, liquids like liquid nitrogen, methane, ammonium, various alcohols and even acid solutions.
 

The Horta, as the mysterious native life form of Janus VI refers to itself, defends itself and digs tunnels in solid rock using a strong acid. It´s curious to note that certain acids, like sulfuric and hydrocyanic acid could act as solutions for an extraterrestrial metabolism.
 

However silicon as replacement to carbon has also it´s disadvantages. Complex silicon compounds are unstable and ineffective under terrestrial conditions. McCoy notes this, claiming that silicon life would not survive in the artificial (?) human environment created on Janus VI. But as it seems the creature called Horta comes from within the planet, where may suitable conditions exist. Silicon life forms may could exist in oxygen-free or poor  (as oxygen would oxides the silicon molecules), dry and very cold environments.  Such for humans highly prohibitive conditions would also reduce the metabolism and reproduction rate of this hypothetical life form, may we would not even realize that it is alive. In the Star Trek episode the Horta is the last of it´s kind, only the eggs – appearing to us like inanimate silicon-concretions - survive, however needing thousands of years to develop and be finally ready to hatch.
 

One of the great strengths of Star Trek was to pose both ethic as intriguing scientific questions, may some will be answered by future generations, when they one day may really encounter life, but not as we know it ... I find that a fascinating vision for the future!
 

Bibliography:
 

FOURESTIER, J. de (2005): The Mineralogy of Star Trek. Axis, Vol.1(3): 1 - 24
PICKOVER, C.A.(1999): The Science Of Aliens. Basic Books: 240
SHOSTAK, B. (2012): Life in the Universe. Addison-Wesley Publisher: 544
SCHULZ-MAKUCH, D. & IRWIN, L.N. (2006): The prospect of alien life in exotic forms on other worlds. Naturwissenschaften. Vol.93: 155-172

The Geology of Star Trek: I. Minerals, Crystals and Alien Life Forms

„But a geological oddity to say the least. Pure silicon!“

„A few trace elements, look, we didn't you call here so you could collect rocks!“ 

Geologists get no respect, even if vital for entire civilizations, from the episode “The Devil in the Dark”.

According to Vulcan philosophy one should respond with grief only if a life was lost in vain. The loss of Mister Spock - more precisely of actor Leonard Nimoy – last week was followed by worldwide reactions, remembering him both in his role as a real person. I think Nimoy would have liked it, as it obviously shows that he left a lasting impression on our pop-culture.

So here is my geological-geeky tribute to his impersonation of the 1th science(including geology) - officer on board of the USS Enterprise and the geology of the Star Trek universe.
 

Geologists seem to be a quite common race in the Star Trek universe. According to "Star Trek - Enterprise" (and alluded in the movie "Star Trek: First Contact")  one of the first contacts of humans with an alien species occurred when the crew of a geological exploration mission crash-landed on earth and was forced to work in a coal mine in Pennsylvania.
This seems logical. Mining activities for raw materials and fuel are also widespread in the Star Trek universe. As every space-civilization would soon or later exhaust the resources of its own planet, there is an urgent need for specialists of extraplanetary geology.
 

Subterranean mining facility on Janus VI, essential for providing thousands of worlds with metals and other precious resources.
 

In many episodes of the original Star Trek series the crew of the Enterprise visits mining-colonies on foreign planets or searches for valuable minerals and crystals, there is even a geological tricorder available and how I did love to be able to access the mineralogical database in it. 
By convention the names of terrestrial minerals (a crystalline combination of one or various elements) end with the suffix "-ite", the denominations of elements with the suffix "- ium", "-um", "-on", "-gen" or "-ine". Unfortunately it seems that this nomenclature is not always applied with the necessary scientific accuracy by the Enterprise crew, but as those are (to us) unknown materials, it may be excused. 

Unknown elements, forming also unknown minerals, are not a scientific impossibility. The heaviest elements human science knows posses an atomic weight of 118. These elements are unstable and radioactive. However it may be possible that still unknown elements with an atomic weight, higher than 184, are stable and exist somewhere out there. 
Could these unknown elements form also minerals? Without facts it is vain to speculate. In meteorites we have found almost 300 different minerals, based on known elements, however formed under extraterrestrial conditions and therefore not found in earth´s environments. Iron-, magnesium-, calcium-silicates prevail, but also iron- and nickel-alloys, maybe forming also earth´s inner core but unknown on it´s surface.
 

More than 125 minerals are mentioned in the original Star Trek episodes, movies, animation series and the recent TV-reboots, however of these only 23 are actually real terrestrial minerals and only one mineral - olivine - has actually been found in extraterrestrial rocks. Curiously quartz, one of the most common minerals on earth, is almost never mentioned but specimens are used as props for dilithium crystals. In the Star Trek universe lithium or dilithium (spelling used in later episodes) is the only material that can be used in matter-antimatter reactors, standard equipment on board of federation spaceships. As its (supposedly) cubic crystal structure can filtrate antimatter it therefore can be used to control the energy output from the reactor. As some real minerals can filtrate or distort certain wavelengths of visibile light, it may be not a so far-fetched physical property after all.
 

Dilithium crystals are frequently referred in the original Star Trek series, also as gemstones, however they play a vital role in the episode "Elaan of Troyius". Here Mr. Spock and Scotty must repair the damaged energy converter of the USS Enterprise, a very delicate operation as they must rely on crude dilithium crystals, also the Klingons are attacking...
 

Gemstones like sapphires, diamonds, emeralds or rubies, all these crystalline forms have a great appeal to humans, but are just carbon, aluminium or silicon-oxide varieties ... quite illogical (from the episode “Cat´s Paw”).
 

Common salt plays an important role in the episode "The Man Trap" (it was also the first episode of Star Trek ever broadcasted, as the other episodes were rejected at first. In the original pilot episode, "The Cage", however there features also a geologist and a geological report). A remote outpost is infiltrated by a shapeshifting creature. Only using some halite (the mineralogical term for salt) as bait, the creature, in desperate need to feed on this mineral, will reveal it´s true form.
 

Collecting (literally) rocks in the Star Trek universe...

Sulfur, saltpeter and carbon (in two crystalline modifications, as coal and as diamond)  saved Captain Kirk´s life in the episode "Arena". Kirk is forced into a battle against the almost indistructible Gorn, a reptilian life form with armored skin. Only by using the naturally occurring outcrops of the mentioned elements and minerals on a desolate planetoid, Kirk is able to build a primitive gun. Using the sulfur, saltpeter and coal to make gunpowder and the pointy diamond-crystals as high-impact projectiles, he finally puts down his adversary for good (unfortunately the supposed "diamonds" have the wrong crystal shape).
 

However sometimes minerals can also cost a life. During negotiations for the mining rights of the rare but essential (and also non-existing) mineral topaline, a red-shirt is killed in the episode “Fridays Child” on the surface of Capella IV, just 32 seconds after beaming down…
 

He´s dead Jim, just 32 seconds after arriving on the surface of Capella IV …
 

It´s curious to note that hand lens or geological hammers are of no use in the 23th century. In the episode "Obsession" Spock analyzes a rock composed of the mineral tritanium with the already mentioned tricorder. Tritanium is 21.4 times as hard as diamond (curiously Kirk in the episode "Arena" states that diamonds are the hardest substance known in the Star Trek universe!?), therefore useful for the construction of indistructible spaceship hulls (which begs the question what phenomenon could erode and smooth the boulders found on the surface of Argus X). The rock can be sampled only by phasering off a piece, since it is too hard to cut with normal tools.
 

Shoot to sample...
 

However even the most sophisticated technology can´t replace geological intuition - It is not logical, but is often true. On Gamma Trianguli VI (episode “The Apple”) Spock immediately notes the lush vegetation, deducing correctly that also soil-nutrients and therefore geology plays a role in supporting this peculiar paradise-like world. With his sharp geological eye Spock identifies also hornblende and quartz in a rock (according to petrological composition may an igneous rock?), easily erodible (and explosive!) and so may the source of the rich soil.

But maybe the most fascinating incarnation of geology in the Star Trek universe is the encounter with silicon-based life forms (to be continued...)

Bibliography:

FOURESTIER, J. de (2005): The Mineralogy of Star Trek. Axis, Vol.1(3): 1 - 24
PICKOVER, C.A.(1999): The Science Of Aliens. Basic Books: 240
SHOSTAK, B. (2012): Life in the Universe. Addison-Wesley Publisher: 544
SCHULZ-MAKUCH, D. & IRWIN, L.N. (2006): The prospect of alien life in exotic forms on other worlds. Naturwissenschaften. Vol.93: 155-172

Geologists in the land of the Kangaroo

Terra Australis - the southern continent had been “discovered” by Europeans already in 1606, but only in 1642 the size of the new “island” becomes clear and the first geological observations  were made only in the early 19th century.

October 1800 two ships – the “Geographe” and the “Naturaliste” – set sail from the harbor of Le Havre, France. Under the command of Captain Nicolas Baudin (1754-1803) geographers, astronomers, artists, naturalists, zoologists, botanists, and 2 mineralogists – Louis Depuch (1774-1803) and Charles Bailly (1777-1844) – were instructed to explore, map and eventually claim for France new territories of this new world. In the last moment also the young zoologist, and trained paleontologist, Francois Auguste Peron (1775-1810) joined the expedition.

The geological observations made by Depuch (died during the expedition) are known from various reports send to Baudin. Bailly will publish some notes after his return to France and Peron included his research in the official report of the expedition.

In May 27, 1801 the bare land of Cape Leeuwin was in sight and the naturalists went on land along the Wonnerup Inlet, where they collected the first specimens of Australian animals, plants and rocks.

 

Fig.1. The “Baudin” – expedition, route drawn on Louis de Freycinet´s (1779-1842) “Carte générale de la Nouvelle Hollande”, published in 1811 as part of the results of the 1800-1804 expedition.

A storm forced the men to remain on land for several days and one man died during a failed attempt to reach the ships (during the entire expedition 32 men died, 13% of the crew, a surprising low percentage considering the period). The storm separated the two ships, the “Naturaliste” proceeded to the island of Timor, a Dutch colony at the time, where the crew fell ill with Malaria and other tropical diseases. The “Geographe” approached in November 1801 the island of Tasmania, where the expedition will stay for three months.
April 1802 the “Geographe” meet the British vessel “Investigator“. The expedition of the “Investigator” will map large parts of South-Australia and prove that Australia is one large continent, not two islands separated by a sea strait, as some geographers assumed. This was a disappointing discovery for captain Baudin, as there was no apparent geographic separation between the territories already claimed by British explorers, the entire continent had to be considered of British domain.

Captain Baudin, the crew and the naturalists could now only hope to gain some fame with the scientific results of the expedition...

The geologists Depuch and Bailly used a rock classification scheme, developed by the famous French geologist Déodat de Dolomieu, with four categories. They recognized primary rocks, such as granite; secondary rocks, such as stratified sandstone and limestone; alluvium (recent deposits) and volcanic rocks, such as basalt. The presence of these rocks in Australia was an important discovery, it proved that the classification scheme developed in Europe could be applied worldwide.

 

Fig.2. Charles-Alexandre Lesueur´s and Nicolas-Martin Petit´s depiction of Van-Diemen´s-Land for the “Voyage de decouvertes aux Terres Australes“. The two young men – unskilled workers at the beginning of the expedition -  were invited by Baudin to illustrate the logbook  -  both will become the most skilled artists for animal- and plantlife of the time. The granitic rocks found on the island of Tasmania convinced Peron and the other geologists that the most ancient – the primary – rock was Granite, forming the basement of all continents.

Paleontologist Peron noted along the west coast of Australia horizontal sand- and limestone layers (the Tamala-Limestone) and concluded, based on similarities to recent sediments, that these layers were deposited along an ancient beach, implying substantial variations in the sea level during geologic time:

“One of the greatest achievements of modern geology research and also one of its most indisputable, is the certain knowledge that, in the past, the level of the sea was higher than at the present time. At almost all places in the old and the new world is the proof of this phenomenon as numerous as it is evident. Only in les Terres australes was this still to be ascertained as, by virtue of its immense areal extent, it could have proved to be an important exception to the universality of the former domination of the ocean over the land.” 

(PERON & FREYCINET 1816)

Unfortunately the return to France will be disappointing for Peron. Captain Baudin dies on the island of Timor and French authorities will show little interest in the 220.000 samples of animals, plants and rocks, the 73 living animals, 3 kangaroos, 2 emus and 3 wombats brought back to Europe.

Peron publish his report “Voyage de decouvertes aux Terres Australes” only in  1807, after a long struggle for money and dies just three years later, before the completion of the second volume. However the sea shells collected during the expedition will be studied by an important French naturalist – Jean-Baptiste de Lamarck. In 1804 Lamarck publishes his theory about the transmutation of species, based in part of the observation that the fossil shells found in the sediments of France are similar, but not identical, to shells of living molluscs collected in Australia.

 

Fig.3. Peron discovers on the shores of Tasmania a living clam with a peculiar triangular shape – Trigonia antarctica – a genus of bivalve known only from fossils found in the sediments of the basin of Paris. He notes the similarities of this living specimen with fossil specimens – an important step to consider a relationship between fossil and extant species. Image of Trigonia sp. from Cretaceous sediments of Bavaria.

Unfortunately for Lamarck – and the naturalists of the Baudin expedition – he mixed his careful observations with wild speculations. Lamarck noted variations of organisms in time, however he could not explain why such variations occur or why certain organisms went extinct or survived – apart invoking a final cause and implying a sort of supernatural scheme. Geologist Charles Darwin will later regard Lamarck’s work as “useless“...

Fig.4. Geological map by Jules Grange, published in 1850, surprisingly little was known of the geology of Australia until the 20th century.

Bibliography:

GLAUBRECHT, M. & MERMET, G. (2007): Josephines Emu oder Die Geschichte einer vergessenen Expedition. GEO Nr.6/2007: 98-122
MAYER, W. (2008): Early geological investigations of the Pleistocene Tamala Limestone, Western Australia. from GRAPES, R.H.; OLDROYD, D. & GRIGELIS, A. (eds) History of Geomorphology and Quaternary Geology. Geological Society, London, Special Publications 301: 279-293
MAYER, W. (2009): The Geological Work of the Baudin Expedition in Australia (1801-1803): The Mineralogists, the Discoveries and the Legacy. Earth Sciences History Vol.28 (2): 293-324
RUDWICK, M.J.S. (2005): Bursting the limits of time – The reconstruction of Geohistory in the Age of Revolution. The University of Chicago Press, Chicago, London: 708

"What a confusion for Geologists" - Geologizing with Darwin

The first stop of the voyage of the Beagle (1831-1836) was “Quail Island” (today Island of Santa Maria) – a small island located in the bay of Praia of the larger island of St.Jago (today Santiago, Cape Verde Islands). This visit is especially interesting as it provides some glimpses in Darwin’s geological background at the beginning of his adventure and his later “evolution” as geologist.
 

Darwin collected basic experience as geologist during a field trip across Wales and surely know the geological theories of the time, especially regarding the formation and age of the earth. The notion of a 6.000 year old earth was already dismissed by scholars and even the interpretation of gravel and sand deposits as the remains of the biblical flood (the “Diluvium“) was questioned. However the notion of earth’s history of a succession of catastrophic events was still fiercely discussed.

Many geologists at the time proposed that geologic processes in the past differed significantly from recent processes; even certain types of rocks (and the formation of these rocks) were limited to certain time periods, when today unknown geological processes were shaping the earth. The lawyer Charles Lyell challenged this interpretation of earth’s history, arguing that common and slow processes still observable today also acted long time ago.

Captain FitzRoy offered Charles Lyell’s recently published and controversial “Principles of Geology” as welcoming gift, but Darwin probably didn’t find time to read the book in the first weeks of the expedition. His former mentor, botanist John S. Henslow, even “advised me to get and study the first volume of Principles, which had then just been published, but on no account to accept the views therein advocated.“

It’s therefore even more surprising to read in Darwin’s autobiography (1876-1881) the following phrase:

“The very first place which I examined, namely St. Jago, in the Cape de Verde islands, showed me clearly the wonderful superiority of Lyell’s manner of treating geology.”

Darwin also emphasises how the visit of St.Jago converted him to Lyell’s geology:

“The geology of St. Jago is very striking, yet simple: a stream of lava formerly flowed over the bed of the sea, formed of triturated recent shells and corals, which it has baked into a hard white rock. Since then the whole island has been upheaved. But the line of white rock revealed to me a new and important fact, namely that there had been afterwards subsidence around the craters, which had since been in action, and had poured forth lava. It then first dawned on me that I might perhaps write a book on the geology of the various countries visited, and this made me thrill with delight. That was a memorable hour to me, and how distinctly I can call to mind the low cliff of lava beneath which I rested, with the sun glaring hot, a few strange desert plants growing near, and with living corals in the tidal pools at my feet.“

Fig.1. Profile of the island of St. Jago as seen by Darwin in 1832. Darwin was the first to study the geology of the Cape Verde Islands (from DARWIN 1876). Darwin recognized three distinct layers of rocks, a lower series with volcanic rocks composed of volcanic breccias and magma dikes (deposited under water - identified with "A"), a limestone with fossils ("B") and finally a cover of basaltic lava ("C"). Darwin, trained by Sedgwick, noted also the contact metamorphism between the former hot molten lava and the earlier cool limestone.
It is curious to note that Darwin adopted the geological terms used by German (not British) geologists to describe the rocks observed in the field, here the strong influence of Alexander von Humboldt works, read by the young Charles, is recognizable

Darwin uses in later publications the similarity of the fossils found in the carbonate sediments (Darwin’s line of white rock) and the still living animals on the shore as evidence that no substantial change in the geologic processes forming these rocks occurred over time.  
However from the geological notes he made during the field trip on St. Jago it emerges that young geologist Darwin was still struggling to accept this idea. More important, accepting slow geological processes made it necessary also to accept a very old earth.

During one of his daily excursions on St.Jago Darwin discovered a mature baobab-tree (gen. Adansonia) growing on the bottom of one of the large valleys carved into the hard basaltic rocks of the volcanic island.

“In this [one of the valleys north of Praya] grows the celebrated Baobab or Adansonia; this tree only 45 feet high, measured two feet from the ground round the solid trunk. 35.-Some of the same species in Africa were supposed by Adanson to reach the enormous age of 6000 years.-The very appearance of the tree strikes the beholder that it has lived during a large fraction of the time that this world has existed.“

Darwin notes that a 6.000 year old tree would have experienced a significant period of earth’s history, implying that earth, despite older than proposed by scrupulous clergymen, would be not much older. However the eroded valleys in the thick lava shields, characterizing the landscape on St. Jago, need vast periods of time to form, as he continues:

“Of course the valley must be older & it is this one that has finally left the neighbourhood of Praya in the state we now find it.-How long a time intervened between this period and the deposition of former beach it is impossible to say.-during it three great phenomena occurred, the flowing of the lava.-the upheaving of the coast. & the great beds of diluvium collected in the older valley.-To what a remote age does this in all probability call us back & yet we find the shells [in the 'former beach'] themselves & their habits the same as exist in the present sea.“

In the final note Darwin considers the possibility that the similarity between the fossil shells and the recent ones could also be explained by a short interval of time between the formation of the white rock and the deposition of modern beach deposits (so there was no time for a faunal turnover).
However accepting a young age for the fossil beach deposits and the even younger eroded remains of the volcanic island of St. Jago (the coastal lava shields are covering Darwin´s white rocks and therefore according to stratigraphic principles are younger) would invoke some unknown – and presumably catastrophic – geological event in the not-too distant past to explain its actual deep incised valleys.

“I conceive it to be clear, from the pieces left standing and from the corresponding appearance on each side of the valley, that the country was originally covered with a uniform bed of this rock.-and that after being shattered by some great force: these valleys were formed by the agency of large bodies of water: To this latter force the valleys nearer the coast give abundant evidence.“

Darwin will admit in his diary “what a confusion for geologists.“

To be continued…

Bibliography:

CHIESURA, G. (2010): A Santiago sulle orme di Darwin. Darwin – Bimestrale di Scienze No.40: 32-36
CHIESURA, G. (2013): Isole di Darwin – Un curioso in mezzo al mare. CD-Rom
HERBERT, S. (2005): Charles Darwin, Geologist. Cornell University Press: 485
JOHNSON, M.E.; BAARLI, B.G.; CACHAO, M.; da SILVA, C.M.; LEDESMA-VAZQUEZ, J.; MAYORAL, E.J.; RAMALHO, R.S. & SANTOS, A. (2012): Rhodoliths, uniformitarianism, and Darwin: Pleistocene and Recent carbonate deposits in the Cape Verde and Canary archipelagos. Palaeogeography, Palaeoclimatology, Palaeoecology Vol.329-330: 83-100
PEARSON, P.N. & NICHOLAS, C.J. (2007) : ‘Marks of extreme violence’: Charles Darwin’s geological observations at St Jago (Sao Tiago), Cape Verde islands. in WYSE JACKSON, P. N. (ed.) Four Centuries of Geological Travel: The Search for Knowledge on Foot, Bicycle, Sledge and Camel. Geological Society, London, Special Publications, 287: 239-253

"Mad about Geology" - Geologizing with Darwin

"A journey of a thousand miles begins with a single step."
Chinese proverb

January 16, 1832 the H.M.S.Beagle, with Charles Darwin on board, arrived to the barren "Quail Island" (today Island of Santa Maria, Cape Verde Islands). It was the first time that Darwin geologized alone in a foreign country, however he was well prepared...

In 1831 Charles R. Darwin went on a life changing field trip – not to mention the voyage on board of the Beagle later in that year. The botanist John Stevens Henslow introduced the 22-year old Darwin to 46-year old Adam Sedgwick, self-educated naturalist and professor for geology and botany at Cambridge University. Even if Darwin was a student at Cambridge, he seems not to have attended Sedgwick´s lectures on geology, as he regrets in an autobiographic note that

“Had I done so I should probably have become a geologist earlier than I did.“

At the time Sedgwick was studying the geology of Wales and invited Darwin to join him in a field trip from Shrewsbury, Darwin’s hometown. Sedgwick was especially interested in the stratigraphic succession exposed in North Wales (Sedgwick will later use his observations to define the geologic epoch of the “Cambrian“) and Darwin was interested to acquire the basics of geological field work. Darwin wrote in July to a friend

“I am now mad about Geology & daresay I shall put a plan which I am now hatching, into execution sometime in August, …[]“

Darwin was well equipped for his geological field investigation. He purchased a new clinometer with an incorporated compass for structural analysis and a geological hammer for the collection of rocks.
 

He visited Llanymynech (located west of Shrewsbury) alone and "on my return to Shropshire I examined sections and coloured a map of parts round Shrewsbury", mapping outcrops of sandstone and coal measures.

Sedgwick arrived to Shrewsbury on the 2nd August, visiting in the next days some outcrops located south-west of the city, where he recognized limestone and volcanic rocks. It’s not clear if he met Darwin already, for sure both geologist left Shrewsbury on August 5th venturing north. They spend a week trying to find Old Red Sandstone. Sedgwick was interested in the geological formations underlying the Old Red Sandstone (Silurian to Carboniferous in age), as the age of these rocks was still unknown and according to the large-scale geological map published by George Greenough in 1819 such rocks should be found in the area. However despite their combined efforts and a meeting in Llangollen with another great geologist, Robert Dawson, no Old Red Sandstone was found.

In his autobiography Darwin affirms that he left Sedgwick at Capel Curig, however it may be possible that he visited with Sedgwick the island of Anglesey and even made a short trip to Dublin (as Sedgwick did, on Anglesey he found also the Red Sandstone he was after). During his voyage on the Beagle, Darwin will recognize on the Cape Verde Islands Serpentine, this kind of rock he could have only previously seen on Anglesey - or maybe he used Sedgwick notes.

Fig.1. Geology of North Wales, after Reynolds 1860, 1889, Woodward 1904 (click to enlarge), with the route of Darwin and Sedgwick after ROBERTS 2001. The first part of the route, starting from Shrewsbury, follows the contact of the Silurian limestone (pink-coloured) and younger sediments (blue colour; Carboniferous to Permian), as both geologist hoped to find the Old Red Sandstone formation. Sedgwick found it (dark-orange) only on the island of Anglesey.

Twenty pages of notes made by Darwin during this tour are still today conserved – in his autobiography he will later remember: “This tour was of decided use in teaching me a little how to make out the geology of a country…”
 

When Darwin returned home to Shrewsbury August 29th a letter by botanist John Stevens Henslow, in name of Captain Robert FitzRoy, was offering him a position as gentlemen companion and naturalist on board of the Beagle. 

Read on...

Bibliography:

HERBERT, S. (2005): Charles Darwin, Geologist. Cornell University Press: 485
ROBERTS, M. (2001): Just before the Beagle: Charles Darwin’s geological fieldwork in Wales, summer 1831. Endeavour Vol. 25(1): 33-37