Field of Science

Darwin's First Botanizing Steps Followed His Geological Ones

 “I collected every plant, which I could see in flower, & as it was the flowering season I hope my collection may be of some interest to you." - Charles Darwin in a letter to his friend and mentor John Stevens Henslow, 1836.

Charles Robert Darwin's interest in the natural world was widespread. As a student, he loved to hunt animals and collected bugs and minerals. His mentor and friend John Stevens Henslow, mineralogist and professor of botany, introduced the young Darwin to both disciplines. Darwin attended Henslow's botany lectures and field trips each year during his three years at Cambridge, visiting also private meetings at Henslow's home. Here he met with Adam Sedgwick, president of the newly formed Geological Society of London. During a geological field trip in the summer of 1831 with Sedgwick, Darwin collected and preserved also some plant specimens.

Herbarium sheet by J. S. Henslow with three plants collected by Charles Darwin in 1831 at Barmouth, North Wales. This is the earliest-known herbarium specimen collected by Darwin.

During the five-year-long voyage of the Beagle Darwin collected plants or seeds on the Cape Verde Islands, in Argentina, in Uruguay, in Chile, in Brazil and some of the visited islands, like the Falkland, Galápagos and Cocos islands. As Darwin had limited space on the Beagle, most occupied by rocks and animals, he limited himself to remote or poorly studied localities.

Darwin had prepared several thousand labels in different colors before the voyage to be applied to every dried plant (the labels including species, locality, date and his signature). Wet specimens, conserved in "spirits of wine", were tagged with a small, metallic plate. Henslow, who back in England managed Darwin's collection, however, removed most labels when including Darwin's specimens into the herbarium. Unlike the collected rocks and animals Darwin didn't number the plant specimens, so it seems a bit confusion sneaked into the collection. Another friend of Darwin, botanist Joseph Dalton Hooker, lamented to Darwin that not all notes could be attributed to the preserved plants.

Darwin's plant collection is especially interesting as it includes many species from less visited islands of the Galápagos and the Cocos archipelago. Darwin was intrigued about the relationship of the isolated species found on the islands to the species found on nearby continents. Later Darwin conducted experiments with seeds, showing that some can survive salty water for months and so be dispersed by marine currents. Despite Darwin's plans, he didn't publish the collected plants in “The Voyage of the Beagle” (published in 1839), as a very busy Henslow didn't meet the deadlines for publication.

Darwin collected 756 different species, subspecies or varieties of vascular plants during his five years long voyage around the world, 220 species were new to science. Darwin was especially surprised by the variability displayed by plants. A collected grass species was divided by Henslow into fifteen different varieties! This was an intriguing observation, important for his later formulated theory of evolution, how one species can split over time in various new ones. Also, the relationship of plant species on islands to nearby continents was an important observation. The plants from the Galápagos islands showed, according to Hooker, a remarkable variability between the single islands, however some even more remarkable similarities to species from North America and Brazil. Would a divine creator not be able to create distinct, unique species on remote islands as he pleased? However, if seeds can be dispersed with marine currents and islands be colonized by plants from nearby continents, couldn't they also evolve there in new species?

Radioactivity and Earth's Age

In the 19th century, the discrepancy between the age of Earth and the age of the cosmos posed a great problem to scientists. Geologists had calculated, using methods like erosion or sedimentation rates, ages for Earth spanning from three million to fifteen billion years. Physicists and astronomers, based mostly on the energy output of stars, calculated an age for the universe spanning from twenty million to ten billion years - so in many models of the cosmos, Earth seemed to be too young or too old to fit in. In August 1893, during a meeting of the American Association for the Advancement of Science, geologist Charles D. Walcott (1850-1927) summarized the debate as follows:

"Of all subjects of speculative geology, few are more attractive or more uncertain in positive results than geological time. The physicists have drawn the lines closer and closer until the geologist is told that he must bring his estimates of the age of the earth within a limit of from ten to thirty millions of years. The geologist masses his observations and replies that more time is required, and suggests to the physicist that there may be an error somewhere in his data or the method of his treatment."

In 1896 the French physicist Henri Becquerel (1852-1908), based on Conrad Röntgen's (1845-1923) research, discovered that naturally occurring elements, like uranium, also emit X-rays and in 1897 Polish physicist Marie Curie (1867-1934) coined the term radioactivity to describe this energy of unknown origin. Her husband, Pierre Curie (1859-1906), realized that this energy from radioactive decay must be considered when calculating the age of Earth. Physicists supporting a young Earth based their calculations on a quickly cooling Earth. However, radioactive decay in Earth's interior provided a continuous source of energy and heat, therefore Earth was cooling slowly and so could be quite old.

Radioactive decay or another similar long-lasting and high-energy source (nuclear fusion was discovered later) could also explain how stars could produce light and heat for very long periods of time. The notion that stars or the sun had to be young (in most calculations younger than Earth) could also be dismissed.

But even better - the discovery of radioactivity provided not only indirect evidence of an old Earth but by measuring the constant decay it was also possible to calculate the exact age of a mineral, a rock and even of Earth.

High-energy rays, derived from radioactive decay, form a halo of alteration around a mineral grain in the larger biotite-crystal, image from J. JOYLE (1909): Radioactivity and geology, an account of the influence of radioactive energy on terrestrial history.

The British Diplomat Who Studied Volcanoes

When, in 1631, Vesuvius erupted violently after having been dormant for more than 300 years, it aroused great interest among Europe's elite. German Jesuit and naturalist Athanasius Kircher traveled to Southern Italy to study Vesuvius, descending even in the crater. The volcano was almost continuously active, especially after 1750 and Naples became part of the cities traveler should visit when in Italy.

Sir William Hamilton (1730-1803) was a British diplomat in Naples from 1764 to 1798, He got so interested in the nearby Mount Vesuvius that in 1776 he published a monograph on the mountain, illustrated with stunning artwork by local painter Peter Fabris. Hamilton's "Campi Phlegraei: Observations on the Volcanos of the Two Sicilies" is considered a pioneering work of early volcanology.
 The eruption of Mt. Vesuvius in August 1779.
The eruption of May 1771. An Aa lava flow (recognized by the broken surface texture) passes the observer's location and reaches the sea at Resina. Note the steep, slowly advancing front of the flow. Pietro Fabris is amongst the spectators (below left) as is William Hamilton, who explains the view to other onlookers.
Inside the crater of Mount Vesuvius.

Lava samples from Mount Vesuvius.

Another view of the August 1779 eruption of Mount Vesuvius.

The excavation of the Temple of Isis in Pompeii.
 Hamilton at the crater of Forum Vulcani (Solfatara near Pozzuoli), examining the sulphur and arsenic deposits near the hot springs.

Hitler's Geologists

Already during the first World War the Germans established a special class of soldiers known as "Kriegsgeologen", military geologists working on the front line in special offices called "Geologen-Stellen". Their tasks included solving water supply issues by locating the best spots for wells, locating rock-materials for construction or roads and choosing sites suitable for bridges, trenches and galleries. 

In 1936 Adolf Hitler, now the Führer of the German Reich, announced his Four Year Plan to boost economic growth and make the country independent from imports (an important, at the time not mentioned, goal was to prepare the economy for a coming war). This plan included also projects to map all resources available in the Reich, like rare metals and especially oil. Geologists explored old mines to find new veins of ore and until 1939 almost the entire territory of the German Reich was mapped with geophysical methods (like gravimetry and seismic survey), hoping to discover new oil fields. At the beginning of World War II. many geologists were incorporated in the "Ahnenerbe", a unit established by Heinrich Himmler, the Reichsführer of the Schutzstaffel. The Schutzstaffel (or SS) was a vast military organization inside the Nazi regime, controlling the police, secret police, troops but also business like quarries and mines. The Ahnenerbe was the "science institute" of the SS, dedicated to geological, archaeological and ethnological surveys, but also political propaganda and pseudo-scientific research.  

Reichsführer SS Heinrich Himmler visiting a quarry in southwestern Germany, 1935.

During the field campaign to invade Poland in 1939 it was decided to establish also an "Oil Kommando", a unit of 50 geologists mapping oil reserves in occupied areas. The reserves in Germany and occupied areas were not sufficient to keep the German forces running for long. When Hitler ordered to attack the Soviet Union in summer of 1941, he hoped also to secure the rich oilfields of the Caucasus and Crimea where 80% of the Russian oil came from. Geology became now part of the war efforts and Himmler established in April 1941 the "SS-Wehrgeologen Battalion 500", the Schutzstaffel equivalent of a unit of military geologists. The battalion comprised four units, a unit specialized in the construction of tunnels (the "Stollenbau Kp"), a unit of hydrogeologists, a unit of Earth scientists (ranging from archaeologists to geophysicists) and a unit specialized in drilling operations. Members were recruited from other SS units including the Ahnenerbe. The unit included experts like Erich Marquardt, an archaeologist, Karl Heinzelmann, a geologist who worked on tectonics, and Joachim Schlorf, who studied the toxic effects of Vanadium-ore. The unit was commanded by Rolf Höhne, an archaeologist and geologist. The official tasks of the Wehrgeologen included all aspects of military geology, like prospecting for water, oil, gas and other valuable resources in the field, support during construction work of fortifications, underground mines and galleries. One project included mapping the route for a planned “Autobahn” (highway) between Berlin and the peninsula of Crimea (never realized). 

Geophysical surveys carried out until the beginning of the war in 1939. After BENTZ and CLOSS 1939.

However, more esoteric tasks included archaeological digs to prove the superiority of the Aryan race and research in ancient artifacts and unknown energy sources. Rolf Höhne believed in the Hollow Earth theory and published various archeological and pseudo-scientific articles on the topic. The Hollow Earth was a theory dating to the early 19th century, claiming that after a series of natural disasters a race of superior beings survived in a vast undergroudn reign, accessible only be gateways hidden in the mountain ranges around the globe.

In 1943 the Wehrgeologen were sent to northern and southern Europe to help build a defense line along the coasts of France and in the Italian Alps. The "Blaue Linie" was a system of fortifications to be built in the Prealps to stop the allied forces, landing at the time Sicily. An even more ambitious plan included the idea to use the mountains as the  “Alpenfestung”, a mountain fortress as a last refugium for the Nazis. In the Bretagne and Normandy, they helped to plan a defense line against a possible invasion by allied forces from the sea. The "Hindernisbau" consisted of a system of antitank obstacles along the beaches, bunkers hidden in the rocky cliffs and areas to be flooded in case of successful landfall of allied troops. In France and the Netherlands, the geologists studied the best location to build the launch pads for the secret rocket project of the Reich. The ground had to be stable enough to absorb the vibrations caused by the launch of the Vergeltungswaffe V1 and V2.

A V2 on the launch ramp. Called the 'flying bomb', it was used by the Germans to bomb English cities towards the end of the war.

The Wehrgeologen Battalion now included 600 men, both academics as soldiers. When air raids became more frequent over Germany in the last years of the war, mines or galleries were used to store ammunition and later also to host industries of strategic importance, like weapons production and research labs. Also, new underground bunkers were excavated, often involving forced labor of inmates of concentration camps. More than 800 subterranean bunkers and galleries are mentioned in contemporary documents, 400 still exist today.

In spring of 1945, shortly before the defeat of the Reich, the Stollenbau Kp helped in the construction of "Klein Berlin", a vast system of underground bunkers located beneath the Italian city of Trieste. During this operation, the geologists explored also caves and ancient mines, in part prospecting for valuable minerals, but also searching for the mystic gateway to an ancient underground reign. Based on research by two members of the Ahnenerbe, Wilhelm Teudt and Josef Heinsch, the city of Triest was built supposedly over a force field, the "Heiligen Linien", of subterranean origin. Nazi geologists searching the gateway to the Hollow Earth sounds like the plot for a bad movie. This should not hide the cruel reality of the war and the regime. The SS Wehrgeologen were also involved in war crimes, like the assassination of civilians in the Italian village of Laita.

How WWI Bombs Shattered Bedrock And Changed Geological History

The war in Europe began as a battle between infantry and cavalry, like in old times, and was believed to be quickly over. However, new weapons, like the machine-gun or heavy artillery, made direct attacks almost impossible as soldiers were killed in their thousands. The war quickly became a war of attrition as both sides dug in in a network of trenches and tunnels separated by the “No Man’s Land.” One hundred years after the end of World War I traces can be still found in the landscape.

Alpine Tsunami

Strange as it may seem,  also high in the mountains there is a tsunami risk.

In the Alps, various event can trigger a tsunami, like earthquakes, landslides or glacial lake outbursts. The 1806 tsunami of Lake Lauerzer (Switzerland) was caused by a large landslide and killed almost 500 people. 

Painting of the 1806 tsunami of Lake Lauerz made by David Alois Schmid, who observed the disaster from his hometown Schwyz.

In September 1601 an earthquake hit the area of Lake Lucerne. The 5.9 magnitude earthquake triggered both an underwater landslide as a rockfall from the nearby Bürgenstock mountain. The resulting wave was almost four meters high and inundated  "a thousand steps" (50 to 100 meters) broad area around the lake. Eight people were killed.  In 1867 a second wave caused widespread destruction.  As no earthquake was recorded before the tsunami, experts believe that the collapse of lake sediments and an underwater landslide caused the wave. 

In October 1963 the entire slope of Mount Toc in the Italian Dolomites collapsed. Within 30 to 40 seconds estimated 240 to 270 million cubic meters of rock plunged into the reservoir of Vajont, filling the 400 meters deep gorge behind the dam. The wave generated by the impact of the landslide traveled 140 meters up on the opposite shore, reaching some buildings of the village of Erto. At the moment of the impact,the reservoir contained 115 million cubic meters of water. The landslide pushed part of the water out of the lake, producing a wave with a maximal height of 230 to 240 meters. 

A 100 to 150 meters high wave rushed into the gorge of the Vajont, in direction of the larger and inhabited Piave valley. There the wave destroyed the villages of Longarone, Pirago, Villanova, Rivalta and Fae, and in less than 15 minutes more than 2,000 people were killed.

Glacier outburst floods (GOF) refer to the rapid and sudden discharge of water from within a glacier or from an ice-dammed lake. In the Alps and Cascades most outburst floods occur in the summer, when the melting glaciers provide large quantities of water. In the Andes and the Himalaya also another type of floods is common, outbursts from moraine-dammed lakes, referred to as glacial lake outburst flood (GLOF). Floods resulting from moraine-dam failure have been increasing in frequency in the Himalaya over the past 70 years. One of the best-documented examples happened in August 1985, when the terminus of the Langmoche Glacier in the Khumbu Himal collapsed into the Dig Tsho glacial lake, triggering a wave overflowing the moraine. The wave destroyed a power plant and five people were killed.

Laguna Paron (Cordillera Blanca, Peru) in 2009, a lake dammed by the glacier Hatunraju with a capacity of 75 million cubic meters. The lake is surrounded by a 250 meters high moraine.  If this dam fails an outburst of around 50 million cubic meters could flood the valleys downstream.
The worst glacial lake outburst in historic time was caused by the failure of such a moraine-dam in Peru, when in December 1941 the town of Huaraz was partially destroyed by a flood, 60.000 people were killed.

It’s sedimentary, my dear Watson

February 20, 1949 Mrs. Henrietta Helen Olivia Roberts Durand-Deacon, a wealthy widow, disappeared from the Onslow Court Hotel located in South Kensington, London. The police interviewed the residents and soon John George Haigh became a suspect, as he was the last person to have be seen together with the woman. He led the police to an old storeroom on Leopold Road in Sussex, where they discovered strange and suspicious tools – a revolver, some rubber protective clothing and three containers filled with sulphuric acid.

During the interrogation Haigh suddenly confessed to an incredible crime, “Mrs. Durand-Deacon no longer exists. She has disappeared completely, and no trace of her can ever be found again. I have destroyed her with acid. You will find the sludge which remains on Leopold Road. But you can’t prove murder without a body.” 

Fortunately, Haigh ignored one important fact in his euphoria: the law doesn’t require a body to incriminate him – it requires a corpus delicti - the evidence that a murder happened. Forensic pathologist Keith Simpson examined carefully the ground at the supposed crime scene. He noted something unusual, a small pebble which he described as follows: “It was about the size of a cherry, and looked very much like the other stones, except it had polished facets.“ Simpson realized that he had found the evidence to prove the murder. The pebble was a gallstone from poor Mrs. Durand-Deacon. Gallstone can form from calcium-salts and organic substances in the gallbladder. A thin layer of organic matter protected the pebbles from being dissolved in the acid. John George Haigh, who was ultimately suspected of committing an entire series of murders, was sentenced later to death.

This forensic case was an unusual example of how rocks can help solve a crime. However already in the mid of the 19th century people realized that rocks, soils and the science of geology could be used to reconstruct a crime and provide circumstantial evidence to connect a suspect with the crime scene. An 1856 one issue of the magazine “Scientific American” reported the “Curious Use of the Microscope” to help clarify a case of thievery:

Recently, on one of the Prussian railroads, a barrel which should have contained silver coin, was found, on arrival at its destination, to have been emptied of its precious contents, and refilled with sand. On Professor Ehrenberg, of Berlin [1795-1896, famous zoologist and geologist] from Leipzig in, being consulted on the subject, he sent for samples of sand from all the stations along the different lines of railway that the specie had passed, and by means of his microscope, identified the station from which the interpolated sand must have been taken. The station once fixed upon, it was not difficult to hit upon the culprit in the small number of employees on duty there.

Influenced by the rapid development of science, the British author Sir Arthur Conan Doyle introduced in 1887 a new kind of detective, who based his crime solving abilities on the scientific and forensic clues that everybody acquired or left behind by touching objects, or simply walking on muddy ground: “Knowledge of Geology. – Practical, but limited. Tells at a glance different soils from each other. After walks has shown me splashes upon his trousers, and told me by their colour and consistence in what part of London he had received them."

About at the same time as Doyle published his fictional adventures, the Austrian professor of criminology Hans Gross (1847-1915) published various textbooks dealing with forensic investigations methods. In his “System der Kriminalistik” (Criminal Investigation, published in 1891) he proposed that the police should carefully study geomorphological maps, to infer possible sites where criminals could commit crimes or hide bodies – like forests, ponds, streams or sites with a well. In 1893 Gross published his “Handbuch für Untersuchungsrichter” (Handbook for Examining Magistrates), where he explained how the petrographic composition of dirt found on shoes could indicate where a suspect went previously. Based on these ideas, in 1910 the French physician Edmund Locard (1877-1966) established the basic exchange principle of environmental profiling:
Whenever two objects come into contact, there is always a transfer of material. The methods of detection may not be sensitive enough to demonstrate this, or the decay rate may be so rapid that all evidence of transfer has vanished after a given time. Nonetheless, the transfer has taken place.

The German chemist Georg Popp (1867-1928) was the first investigator to solve a murder case by adopting the principles of Gross and Locard and considering soil as reliable evidence. In the spring of 1908 Margarethe Filbert was murdered near Rockenhausen in Bavaria. The local attorney had read Hans Gross’s handbook and know Popp from an earlier case, where Popp connected a strangled woman to the suspect by mineral grains of hornblende found in the mucus of the victim’s nose and under the fingernails of the suspect.
In the Filbert case a local factory worker named Andreas Schlicher was suspected, however he claimed that on the day of the murder he was working in the fields.
Popp reconstructed the movements of the suspect by analyzing the dirt found on his shoes. The uppermost layer, thus the oldest, contained goose droppings and earth from the courtyard of the suspect’s home. A second layer contained red sandstone fragments and other particles of a soil found also where the body of the victim was discovered. The last layer contained brick fragments, coal dust, cement and a whole series of other materials also found on the site where the suspect’s gun and clothing had been found. However, there were no mineral grains – fragments of porphyry, quartz and mica- on the shoes. Since these were found in the soils of the field where Schlicher supposedly worked the very same day, he was obviously lying.

In the last two decades, the significance of forensic geology increased steadily. It is applied not only to connect single suspects to criminal cases, but also to trace the provenience of explosive, drugs or smuggled goods, including wildlife, not to mention the possible applications to detect cases against the environmental law. Forensic geology also proved valuable to reconstruct and uncover modern war crimes.
In 1997 the United Nations International Criminal Tribune for the Former Yugoslavia (UN ICTY) began exhuming five mass graves in north-eastern Bosnia associated with the massacre of civilians in and around the town of Srebrenica in July 1995. Intelligence reports showed that 3 months after the initial executions of civilians, the primary mass graves had been exhumed and the bodies transported over a 1-3 day period to a number of unknown (but at least 19) secondary grave sites. To prosecute the suspects, it was necessary to prove that the now recovered bodies came without doubt from Srebrenica, and that therefore the later dislocation of the graves was intentionally to hide these war crimes. Two grave sites were intensively studied and samples of the grave fills and surrounding soils and bedrock collected. Soil samples can be screened by their content of minerals and rocks, the size and form of single mineral or rock grains, biochemistry of organic substances, microbiology, remains of invertebrates and plants and pollen and spores preserved in it. These various parameters can vary in so many ways, every soil can be regarded as unique. Comparing the parameters between samples recovered from the victim or the suspect and collected at the crime sites it is possible to establish a unique connection between them.
During the investigations in Bosnia a clast of serpentinite found in one of the secondary gravesites proved to be the decisive evidence. This greenish rock connected one secondary grave site with only one primary site – only there an outcrop with a serpentinite dyke could be found. Similarity, the presence or absence of particular clay minerals, depending on the surrounding geology of the primary burial site, connected or excluded the primary to the secondary sites.

The list of fascinating or strange cases solved thanks to forensic geology would surprise even Sherlock Holmes himself.