How the Earth made us

"Civilization exists by geological consent, subject to change without notice."

William James Durant (1885-1981),American writer, historian, and philosopher.

"How the Earth made us" is a BBC production of 2010, the documentation explores how geology, geography and climate have influenced civilizations, history and mankind acting through four natural forces (considered once elements) - "Deep earth", "Water", "Fire" and "Wind".

The painting by the Italian Renaissance artist Giuseppe Arcimboldo entitled "The Earth" (1566 ?) is one of a series of depictions of the four elements, earth is here associated to the terrestrial mammals of the world (especially the stag borrowed from the Celtic myth).

The Layers of Earth

"This was the man to whom all things were known;
this was the king who knew the countries of the world.
He was wise, he saw mysteries and knew secret things,
he brought us a tale of the days before the flood.
He went on a long journey, was weary, worn-out with labor,
returning he rested,
he engraved on a stone the whole story."

"The Epic of Gilgamesh" (ca 2.000 B.C.)

Single philosophers and scholars already in antiquity noted and philosophized about layers found in some outcrops of rocks. Recognizing fossils as remains of once living sea creatures, some of the Greek philosophers hypothesised that the conformation of land and sea changes over time, and Muslim scholars described the layering of rocks and explained them by accumulation and deposition of rock fragments.
But these great ideas were proposed by single individuals or small groups, and no consistent school of thought or even culture dedicated to the study of rocks developed, most knowledge arise, and soon got lost, and had to be rediscovered again and again during the following centuries.

For example the Italian Renaissance artist and naturalist Leonardo da Vinci studied sediments, their fossils and their stratification on the hills of Tuscany, Romagna and the Po River plain, during his service as an engineer and artist at the court of the Duke of Milan, from 1482 to 1499. From the private notes that Leonardo wrote, it appears that he understand the mechanisms of sedimentary erosion and deposition, that superimposed layers were formed at different times and that distinct layers of rocks could be traced over long distances. This empirical knowledge was "applicated" by da Vinci in some of his paintings, when the landscapes in the background of a scene displays outcrops of rocks represented correctly with sedimentary layers. However da Vinci never published his ideas and it is even questionable if he shared his observations with other persons.

It was the work of the physician Georgius Agricola, latinized version of the German name Georg Bauer (1494-1555) which for the first time contributed to a broad diffusion of applied strata geology. His book "De Re Metallica" ("On the Nature of Metals"), posthumously published in 1556, is a systematic study of ore deposits, the order and extant of strata and especially mining technology, and was to remain the standard text on mining geology for the next two centuries. Agricolas work, as remarkable as it is, was however following the tradition of his times and so mostly specific and descriptive in its content, it offered little or only metaphysic explanations how layers form and how to study them.

It was the Danish Niels Stensen (1638-1686), latinized in Nicholaus Steno, who trained by his anatomical skills, not only recognized the order of layers, but actually tried to explain them and formulate rules for a general interpretation of sediments. Studying the rocks of the Italian region of Tuscany, in 1667 he formulated the main general principles, on which modern stratigraphy is still based:

Fossils are the remains of once living creatures, comparable to modern ones, typically found in sedimentary rocks.

Layers of rock are arranged in a time sequence, with the oldest on the bottom and the youngest on the top, unless later processes disturb this arrangement (principle of superposition).

Layers of rocks are deposited in a horizontal position; any deviations from this position are due to the rocks being disturbed later (principle of original horizontality).

A stratum is deposited continuously unless some other solid body stood in the way (principles of strata continuity).

If a body or discontinuity cuts across a stratum, it must have formed after that stratum (principle of cross-cutting relationships).

Fig.1. Stepwise facies restoration of Tuscan geology based on Earth strata sedimentation and deformation (Niels Steno´s 1669 Prodromus).
Steno explained inclined strata (contradicting his principle of original horizontality) as results of cave collapses or other disturbances. Note also that Steno positioned the single figures to form a sort of cycle of deposition, erosion and collapse.

These simple and general applicable rules could enable naturalists to develop a sort of protocol to be followed when studying sediments, and more important introduced "time" in a stratigraphic succession.
However Steno's work, like many other before him remained for almost a century forgotten. But then John Woodward, considered an amateur physician and naturalist by some, by others a quack, used/stole the principles formulated by Steno in his 1695 book "An Essay toward a Natural History of the earth". The best part of work thought to support the idea of the biblical sin flood as origin of fossils, was regarded the passages copied from Steno.
The shameless book of Woodward however initiated a new interest in the formation of sedimentary rocks and a dispute begun on the origin of fossils. The ideas of Steno were introduced in the academic establishment and adopted in applied mining geology.

Fig.2. In a booklet with the title "Ragguaglio di una grotta ove vi sono molte ossa di belve diluviane nei Monti Veronesi (Description of a cave in the mountains of Verona where many bones of beasts from the deluge can be observed)" the engineer and cartographer Gregorio Piccoli del Faggiol (1680-1755) in 1739 published a topographic map of the Italian Dolomites correlated with a sort of stratigraphic column.
In this column layers of lithologies only some meters thick were depicted as seen in sequence in the field. This work, nearly forgotten at its time and today, is maybe the oldest figure of this kind.

With the formulation of general applicable rules first representations of stratigraphic column appeared at the end of the 18th century; in 1760 the Italian geologist Giovanni Arduino proposed to classify the rocks of the Alps in four distinct layers - primary, secondary, tertiary and quaternary sediments. However the term stratigraphy, as the study dealing with the processes that form sedimentary layers, was coined only in 1849 by the French Palaeontologist d'Orbigny.

Despite the recognition of the principles controlling a succession of layered rocks, the formation of the single strata remained still a mystery. During the 18th and 19th century two models prevailed, the Neptunistic approach proposed that rock strata were crystallized deposits precipitated in a distinct order from sea water, later erosion and modern deposition played a minor role in forming sediments. The Plutonistic approach in contrast stated to erosion and deposition the major role in stratified sediments formation, all rocks are in principle of volcanic origin, and became later eroded and the resulting sediments deposited, there was not so a strict order to observed in the succession of rocks.
The controversy continued for years, no follower of one or the other idea could prove the stratigraphic order necessary for his model. Both models had to deal with the major problem of geology at these times: Geological maps depicted simply the prevailing rock type of an area, connecting single outcrops consisting of the same lithology and implying a spatial homogeneity with surprisingly little diversity and stratigraphic order.

It was the self-educated engineer William Smith (1769-1839) to become the decipher of the code hidden in the rocks itself. He recognized that superficial identical strata differ in their content of fossils - fossils, regarded until them only as curiosities, beautiful, but worthless, became like the numbers on the page of a book an indispensable tool to bring order in the chaos of rocks.

Fig.3. Chronostratigraphy and collection of typical rocks and fossils of the ages of earth - The Layers of Earth as book by Y. Fric, dealer of natural products, Prague 1861 (Collection of the Ferdinandeum in Innsbruck).

Outcrops cold now be correlated not only by their lithology but even more precise by their faunal assemblage.

Smith applied this principle to publish some minor maps in 1799 and then the first large-scale geological map with profiles in 1814-1815, depicting southern England and Wales. His example was soon followed (some say more appropriately copied) by English geologists and by the French naturalists Cuvier and Brogniart, who in 1808 published "Essai minéraligique sur les environs de Paris", a work dealing with the geology of the basins surrounding Paris and completed with a map and geological profiles.
However a detail of the French publication reveals that yet the revolutionary insight of Smith's work wasn't fully grasped by the scientific community, the legend of the geological map doesn't show the lithologies in their stratigraphic (temporal) order like modern maps do, but are arranged by convenience.

Bibliography:

GOULD, S.J. (1988): Time´s arrow Time´s cycle Myth and Metaphor in the Discovery of geological Time. Harvard University Press: 240
KOUTSOUKOS, E.A.M. (2005): Applied Stratigraphy. Topics in Geobiology Vol.23.: 488
LAZZARI, C. (2000): Le Scienze della Terra nel Veneto dale origini ai giorni nostril - 8 secoli di studi, scoperte, progressi e leggende. Societa Veneziana di Scienze Naturali: 171
VAI, G.B. (2007): A history of chronostratigraphy. Stratigraphy, Vol.4. (2/3): 83-97

Archaeopteryx 1861-2011

The year 2011 marks the anniversary of an important paleontological discovery, the first feather and subsequently the first specimen of Archaeopteryx lithographica, discovered in 1861 and today hosted in London.

To celebrate the "Darwin year" 2009 during the Munich Mineral Show there were displayed six (the less known examples, and the single feather counts as entire bird) of the ten recognized specimens of Archaeopteryx, and because it's a rare opportunity, and Archaeopteryx is a pop-icon of earth sciences, here they short stories (P.S. the photos are not the best I have ever made, but the conditions of the display were not optimal).

The first evidence for Archaeopteryx was an imprint of a single feather discovered in 1860 in a quarry near the village of Solnhofen. This fossil was the first evidence for birds in the lagerstätte of the Solnhofer limestone -  and the first evidence for Mesozoic birds.
Studying this feather the German paleontologist Hermann von Meyer proposed to attribute it to the species Archaeopteryx lithographica in 1861, even if today it is not clear if it can be related to the found skeletons in the same formation (one part of this fossil is today hosted in the collection of the Paleontological Museum Munich, the counterpart is treasured in the collection of the museum for Natural history in Berlin).

Fig.1. The famous first feather of a Mesozoic bird!

The fifth specimen of Archaeopteryx to be discovered is the smallest off all and is interpreted to represent a juvenile animal. The fossil is well preserved, especially the skull.
Discovered in 1951, it was first (as many times before and after) mistaken for a pterosaur, and sold to the collector Franz Xaver Mayr, who also in a first moment identified it as Compsognathus, a small dinosaur. After he realized his error Mayr hold the discovery secret until 1972, fearing legal issues.
In 1972 he finally showed the fossil to Peter Wellnhofer, the custodian of the natural collection in Munich. In the following years Mayr and Peter Wellnhofer published the discovery.
Since the opening of the Jura Museum in the (village) city of Eichstätt in 1976 the fossil is displayed in the collection of the Museum.
Fig.2. The specimen of the museum of Eichstätt.

The sixth specimen of Archaeopteryx was recognized during the preparation of the fossil in 1987, it is the largest known and considered a full-grown animal.
Exact location and time of the discovery of this fossil are unknown, during the seventies it was treasured in the collection of the major of Solnhofen - Friedrich Müller. A worker of a quarry near Eichstätt claimed that it was discovered in 1985 and then sold to the major, if so an illegal action, but in 2003 the law case was closed; the provenance of the fossil - the investigated quarry - couldn't be confirmed. Today the specimen can be admired in the Major Müller-Museum in Solnhofen.

Fig.3. The specimen of the museum of Solnhofen.

The eighth specimen was not found in the limestone formation of the Solnhofer Plattenkalke, in contrast to all other fossils, but in the overlying and slightly younger Mörnsheimer Schichten in 1990.
Only parts of the wings and skull are preserved. The exemplar is part of a private collection and still not studied, so the attribution to the genus Archaeopteryx is not confirmed.
Fig.4. The specimen of the Mörnsheimer Schichten, treasured normally in a private collection.

Another fragmentary skeleton is the ninth fossil of Archaeopteryx, the specimen of the family Ottmann and Steil, or "Chicken wing" (the right wing missing parts of the digits) for the press, discovered in 2004. The proportions of the bones are very similar to the other fossil bones of the known Archaeopteryx specimens; the attribution is confirmed also by the recognizable imprints of the feathers.

Fig.5. The "Chicken wing"-specimen.

The Thermopolis-specimen, after the actual location in the Wyoming Dinosaur Centre in Thermopolis, is one of the best preserved fossils of Archaeopteryx, the only displayed outside of Europe and the tenth in the order of recognized specimens. The circumstances of discovery are unknown, in 2001 the fossil was offered for sale, presumably by a private Swiss collector, first to the German museum of Senckenberg, but the costs were to expensive, so finally it was acquired by the Dinosaur Centre and presented in 2005 to the public. In this specimen the preservation of the second digit is notable, like in the Deinonychosauria it could be stretched backwards, an ulterior evidence for the relationships between mesozoic theropods and modern birds.

Fig.6. Thermopolis - specimen.

The curse of the emeralds

"Listen to me,

because I am the first and the last,
I am the one who receives the honours
and the one who despises them...[]
I am the one who has fallen low
and the one who is beyond greatness."
The mother goddess after the ancient texts of Nag Hammadi (II-III century A.D.)

It is unknown when the first emeralds were discovered in the valley of Habach, in the Austrian province of Pinzgau, the only important locality of Europe where these green gemstones can be found.
It is sure that the ancient Romans know the richness in minerals of the Alps, however the oldest confirmed gem from Habach valley is the "Saint Louis" emerald of the French crown, forged in 1226, a 50 carat gemstone which isotopic signature matches the phyllite that characterize the region.
In 1669 the physician and naturalist Nicolas Steno visited a non specified locality in the Alps to study the emeralds found there - maybe it was the Habach valley. In 1797 the mining engineer of Salzburg, Caspar Melchior Balthasar Schroll, notes in his book "Jahrbuch für Berg- und Hüttenkunde", that "emeralds, until now were found only in the valley of Heubach in the Pinzgau".

Fig.1. A single crystal of emerald of the valley of Habach.

Fig.2. ... and many emeralds.

Despite rare and sporadic discoveries of large crystals without inclusions professional mining in Habach valley begun only in 1861. Here, nearly 2.200m a.s.l. tunnels were excavated into the rocks, a sequence of Biotite, Chlorite, Actinolite -and Tremolite bearing schists, rich in beryllium and chromium - essential elements to form under metamorphic conditions the emeralds.

Despite the invested effort, the wealth brought by the mining activities lasted short, in 1913 the English company owning the mine got bankrupt. Various companies and single holders followed in the years, all of them unsuccessful to gain profits from the mines. Then the Great War raged across Europe - there was no more interest in gemstones when people begun to starve.

Fig.3. Description of emeralds of the Habach valley and original specimens from the collection of Georg Gasser (1857-1931), eminent naturalist and author of a book about the minerals found in South Tyrol in the second half of the 19th century.

In 1950 to 1970 various mineral collectors tried their luck, but the hard work, the hostile environment and the isolation demanded a terrible toll - a kind of curse coming with all the things that men so desperately want to possess.
The German Carl Graab, heir of the mine after the second World War, got insane, Sebastian Berger, who some years later leased the mine, one day in 1986 gathered the entire explosive used for mining activity he could find and blasted himself to pieces.

Today the valley of Habach is still an important destination for mineral collectors, some rare emeralds can found in ancient landslide deposits consisting of the emerald bearing lithologies, or in the creeks and rivers coming from the mountains. Even the mine still exist, managed by a private collector, providing rarest specimens of the green fire for the enthusiast, hopefully with curse not included.

Bibliography:

KANDUTSCH, G. & WACHTLER, M. (2000): Die Kristallsucher - Ein Gang durch Jahrmillionen. Bd.2 Christian Weise Verlag, München: 160

A geologist riddle #3

Another geo-riddle, this time a bit challenging...

The photo shows a contact between a greenish in the foreground and a much brighter brownish lithology in the background. The appearance of these rocks reveal that they must have experienced some hard times in the past, but the contact is not the result of tectonic forces.
The green rocks contain a secret, revealed by some creeks in the landscape- a secret which brought great wealth to the inhabitants of the valley...

Further clues to solve the mysterious story of these rocks can also be found on my blog.

Understanding Black Glaciers

Glaciers are often covered by supraglacial debris in their ablation zone, in the Alps these "black glaciers", the geomorphologic term would be Debris Covered Glaciers (DCG), are relatively rare. In contrast such DCG are common in high mountain ranges like the Andes or the Himalaya, probably as consequence of the high sun-radiation levels in these regions.
Supraglacial debris is composed of material transported onto the glacier by rockfalls, avalanches, rubble of moraines and rocks melting out from the ice.

Fig.1. Huge erratic boulder on the Swiss glacier of Vorderaar after a picture published in a travel account of C. Wolf and M. Descourtis in 1785. By providing shadow and shelter to the underlying ice a pillar balancing the rock formed.

The thermal properties of this debris are profoundly different to blank ice and can significantly influence the glacier mass balance. Isolated rocks or a sparse cover, darker then the surrounding ice and snow, tend to absorb radiation of the sun and heat up, melting ice and increasing the loss of a glacier. A sufficient thick cover of rubble however isolates the underlying ice, and prevents or reduces melting and is so decreasing the loss of a glacier.
Research on the Swiss glaciers of Unteraar and Lauteraar have shown that a cover of debris ranging between a thickness of 5 to 20 centimetres shows higher temperatures on the superficial layer than the surrounding environment, however the thermal isolation is sufficient to reduces the ablation of the underlying ice by 32%.
The important influence of the debris cover on glaciers worldwide is however still poorly understand, hard to study and to quantify (variables like what kind of rock with connected physical properties is covering the surface and the highly variable thickness of the debris must be considered) and therefore neglected in many models to calculate future trends .

A new publication by SCHERLER et al. has analyzed 286 glaciers in the Himalaya using satellite images recorded from 2000 to 2008. The research confirmed that more than 65% of the glaciers are retreating with an average of 10 meters per year; however glaciers without debris cover are much faster in this general retreat then glacier with cover.

Fig.2. The glacierized Himalayan border region of Bhutan (bottom) and Tibet (top) seen in a satellite image. From the crest of the mountain range clean glaciers flow northwards onto the Tibetan Plateau, while DCG flow south into densely forested valleys. The debris cover on the glaciers depends of the topography of the surrounding mountains; steep slopes provide much more debris in form of rockfalls than gentle slopes (ASTER-image by NASA, 08 June 2006).

Many of the debris covered glaciers appear to be stable but the underlying ice shows no movement, it has become dead ice - former glacier ice that is not longer connected to the active glacier.

The research shows that to predict the behaviour of single glaciers the debris must be considered, also the comparison between well studied areas, like the Alps, to poorly covered high mountain ranges is not sufficient or even possible, more fieldwork, research and data on the mysterious DCG is essential.

Bibliography:

SCHERLER, D.; BOOKHAGEN, B. & STRECKER, M.R: (2011): Spatially variable response of Himalayan glaciers to climate change affected by debris cover. Nature Geoscience. doi:10.1038/ngeo1068

Namazu: The Earthshaker

According to Japanese myth the cause of earthquakes is the giant catfish Namazu or Namazu-e (the second term refers to the woodcuts of Namazu) living buried in the underground. Namazu is one of the yo-kai (in a very broad sense translatable as "monster"), creatures of Japanese mythology and folklore that were associated or caused misfortune or disasters. By moving his tail he can shake the entire earth and unfortunately he loves to cause trouble and havoc.

Fig.1. Japanese wood-block print showing a mythic catfish that causes earthquakes. Private collection, Berkeley, California (figure from KOZAK & CERMAK 2010). The horizontally outstretched catfish divides the picture in two parts, in the upper part there are rich merchants, in the lower part mourning people who have lost everything by the earthquake. The aftermath of the earthquake is depicted as possibility to redistribute the wealth; rich people have to divide their wealth with the poor to restore the general "cosmic" balance.

Namazu can be controlled only be the god Kashima, which with help of a powerful capstone pushes the fish against the underground and in such doing immobilized him. However the god sometimes got tired or is distracted from his duty and Namazu can move a bit and cause an earthquake.

Fig.2. The god Kashima immobilize with help of a capstone a guilty Namazu, demonstrating to a bunch of small catfishes, representing earthquakes of the past, the severe punishment for their behaviour (here a similar depiction of other punishments). However the catfish tries to defend his behaviour as response to his envy to other fish species, much more appreciated and popular in the traditional Japanese cooking (figure from LEWIS 1985).

Already in the Tokugawa period (1603-1868) the giant catfish was as a river deity associated to natural disasters, not surprisingly caused by water like floods or heavy rainfall. In these early traditions however namazu acts often as a premonition of danger, warning people from an imminent catastrophe or by swallowing dangerous water-dragons prevents even disasters.
Earthquakes, as apparently trembles of earth, were explained by movements of deities or creatures supporting the Japanese main islands, these creatures included gods, giants, an ox, dragons or snakes and a fish.
The dragon was a very old and powerful symbol imported from China and was in old times the main culprit of earthquakes, however during the 18th century, a giant Namazu gradually replaced the giant dragon in the popular imagination. This change from dragon to Namazu was minor, because dragons were also associated to water and rivers and so were closely related to the catfish in the popular imagination.
During the 19th century and after the earthquake of Edo (modern Tokyo) in October 1855 the wrongdoings of Namazu became more a punishment of human greed, it was believed that the catfish by causing havoc forced people to redistribute equally their wealth, in this role Namazu became yonaoshi daimyojin, the "god of world rectification".

Fig.3. Namazu in the form of yonaoshi daimyojin perpetuating his harakiri (in Japanese "Seppuku namazu", 1855) - with his sacrifice he will provide gold and money, dropping from his belly, for the poor people (figure from University Vienna). Some of these depictions have also magical powers: whoever take them home will be protected from earthquakes and experience "10.000 years of luck".

The classic images of Namazu (more than 300 are today known) were mainly a response of the Edo earthquake - by trying to depict also "positive aspects" (redistribution of wealth) of the earthquake the artists hoped to rise the morals of the survivors. Namazu was used also in satire, he is represented as a good-for-nothing, a coward acting only when the gods are gone, a reference to the aristocracy and incompetent civil servants.

Fig.4. A Namazu, representing the earthquake of Edo (modern Tokyo) in October 1855, is attacked by peasants and concubines (here a similar version), in the background help for the catfish is approaching - craftsmen, who will take profit of the reconstruction of the city. The earthquake of Edo, which killed thousand of inhabitants, coincided with the traditional "month without gods", believed a period when all of the gods gather in a secret temple. Taking advantage of the absence of Kashima, the coward Namazu rebelled and caused destruction and sorrows in the human world (figure from Wikipedia).

There are various versions of the myth with slight modifications; in some narratives the god doesn't use a rock, but a sword to nail the Namazu onto the ground. According to another version it is the god Kadori controlling the catfish, with the help of a giant and magical pumpkin. Also the main villain can be represented by a giant eel - Jinshin-Uwo - or a giant earthquake beetle - Jinshin-Mushi.

Fig.5. A version of Namazu controlled by Kashima with a sword (figure from Wikipedia).

Fig.6. ... and Kadori using a giant gourd made of a pumpkin (figure from SanAndreasFault.org).

Fig.7. A picture by the Japanese artist Kadzusa-ya Iwazô of 1842 lampooning the myth of Namazu, a Tanuki (a sort of mythical raccoon-dog with the ability to enlarge voluntarily parts of his body) is subduing the catfish with his giant scrotum (figure from Kuniyoshi Project).

Bibliography:

KOZAK, J. & CERMAK, V. (2010): The Illustrated History of Natural Disasters. Springer-Verlag: 203
LEWIS, T.A.(ed) (1985): Volcano (Planet Earth). Time-Life Books: 176

Online Resources:

SMITS, G. (): Earthquakes in Japanese History. (Accessed 17.03.2011)