Reef geology: studying the sea to understand the mountains

After a longer hiatus a new fieldtrip following the ideas, personalities and outcrops that made the history of geology.

One of the earliest descriptions of coral-reefs comes from a certain Mr. Strachan, who in 1704 submitted to the Royal Society in London a paper about three pages dealing with the subject. He speculated about the formation of this structure, and wrote:

"There are big banks of this coral, it is porous and so hard or yet as smooth as the upright, which grows in small branches. If, of which we speak, is fully grown, others grow in between it, where still others will grow, until the whole structure is as hard as a rock."

This idea of reef-formation was probably not verified in the field, but based on the few travel notions or sparse log book entries brought back from ships venturing in the Indian and Pacific Ocean at these times.
In 1772 to 1775 the German Georg Forster (1729-1798) acted as naturalist on the world-circumnavigation of James Cook, in the years 1773 and 1774 they visited the Pacific Ocean, where Forster studied the atolls and volcanic islands. He observed that corals life in the first meters of the water column, but that the reefs rise up to 300 and 600m above ground. He developed two hypotheses to explain this observation, slow growing the corals raised from the ground, until reaching the surface, where erosion and deposition took place

"They raise their habitation within a little of the surface of the sea, which gradually throes shells, weeds, sand, and bits of corals, and other things o the tops of those coral rocks…[]"

or as alternative, violent volcanic eruptions pushed the corals on the surface.

Fig.1. Atoll as seen in Darwin´s work of 1842: The Structure and Distribution of Coral Reefs.

Darwin during his voyage on board of HMS Beagle (1831-1836) studied Lyell's "Principles of Geology", and the chapter about reefs in the Pacific arouse his interest and his imagination. In Chile, on February 20, 1835, Darwin experienced a very strong earthquake and shortly afterward saw evidence of several meters of uplift in the region, in accordance to Lyell's view Darwin imagined that mountains could rise and sink by many such events during geological time.
Based on the description in the book of atolls, and the possibility of slowly subsidence of earth's surface, and before even seeing a real reef, Darwin developed a preliminary hypothesis to explain the formation of atolls in the middle of the sea, an intriguing geological problem at these times.

"No other work of mine was begun in so deductive a spirit as this; for the whole theory was thought out on the west coast of S. America before I had seen a true coral reef. I had therefore only to verify and extend my views by a careful examination of living reefs. But it should be observed that I had during the two previous years been incessantly attending to the effects on the shores of S. America of the intermittent elevation of the land, together with the denudation and deposition of sediment. This necessarily led me to reflect much on the effects of subsidence, and it was easy to replace in imagination the continued deposition of sediment by the upward growth of coral. To do this was to form my theory of the formation of barrierreefs and atolls."
(Darwin in his autobiography 1887)

Lyell in 1831 could explained fringing-reefs on the coasts of continents by slow subsidence of the landmasses, but didn't extend this idea to the seafloor, Darwin assumed that a single peak of an extinct volcanic mountain, a common feature in the oceans (Darwin had visited various islands of volcanic origin previously), would also experience a slow subsidence, slow enough to enable corals to compensate the down-movement and keep living in the first meters of the water-column, where light and nutrients are available.

Fig.2. Model of atoll formation by reef growth (Darwin, 1842). Darwin proposed that volcanic islands with fringing reefs, islands with barrier reefs and atolls (i.e. ring-shaped reefs without a volcanic island) are different stages of one process, governed by subsidence and reef growth. This famous concept is based on surface examination of reefs and comparison of islands and atolls in different stages of development. Data on the slopes and basins were virtually absent at the time.

Darwin later confirmed his hypothesis by studying reef building organisms and reef morphologies in the Pacific and Indian Ocean (Tahiti in November 1835, Cocos-Keeling Islands and Mauritius in April 1836). He introduced a three-fold classification of reefs that is still used today: fringing reefs, barrier reefs and atolls, also he elaborated a theory that these diverse reefs represent a temporal succession - fringing and barrier reef stages develop around subsiding islands, to became finally an atoll (DARWIN 1837, 1842).
Despite the diligence of Darwin, this work was not comparable with later books, it contains a lot of speculations and superficial observations due the lack of hard evidence, like cores, at these times.

However the theory became soon accepted, Lyell inserted Darwin´s theory in later editions of his "Principles", and the geologist James Dwight Dana (1813-1895), who in 1838-1842 had also visited the Pacific, confirmed most of the observations of Darwin, however recognizing that some areas thought by Darwin to sink didn't in fact show any signs of movements.

Serious critic arouse in the late 1870's, when the German zoologist Carl Semper (1832-1893) in 1868 described on the island of Palau the simultaneous occurrence of the three diverse reef stages, deposing the temporal sequence as seen by Darwin. In 1878 and 1880 the oceanographer John Murray (1841-1914) published his observation made during the Challenger-Expedition (1872-1876) on the islands of Palau and the Fijis. He postulated that reefs grow on submarine elevations of any kind, where organic debris becomes accumulated before dissolving in the seawater.
This new theory was strongly supported and modified by the geologist Alexander Agassiz (son of R. Agassiz) and others. Atolls grew up from shallow submarine summits of various origins, the reef that grows on this bank eventually grows so large that coral the middle of the reef dies, and is dissolved away creating the distinctive shape of an atoll (AGASSIZ 1903).

Darwin responded to Agassiz in 1881, suggesting that the answer could be gained by drilling into an atoll; he assumed that the reef would reach a thickness of 150-180m, below the primary substrate (volcanic rocks for Darwin's hypothesis, or sedimentary rocks for Agassiz's hypothesis) should be found.
In 1896, a Royal Society of London expedition went to the South Pacific to drill beneath Funafuti Atoll in Tuvalu. This expedition was unsuccessful because they were only able to drill down 30m. In 1897 a second expedition drilled down to 210m, and in 1898 they reached a depth of 340m, the outermost limit for the drill-equipment at these times, however still finding calcareous rocks.
In 1951 the U.S. Atomic Energy Commission initialized an extensive drill program to study the structure of the Eniwetok Atoll (Marshall Islands), test site for various nuclear weapons from 1948-1958. This expedition was able to reach a depth of 1,6 kilometres, and finally struck volcanic rock. Darwin had greatly underestimated how thick atolls could be, however it seemed that for the rest he was right.

Even before drilling programs and the use of seismic profiles were available, hinds to understand the structure of atolls came from a very unusual pace, the 2.000m high peaks of the Dolomites in the Alps.
In commission of the Austrian Geological Survey the geologist Baron Ferdinand F. von Richthofen (1833-1905) in 1860 begun to map the area of the valley of Predazzo.
In some stratified sandstones and tuff-deposits he discovered large limestone boulders, some containing fossils and corals, and huge isolated dolomitic massifs emerging from these stratified deposits. Von Richthofen recognized in these particular settings the Darwinian model of atolls - islands of carbonates surrounded by siliciclastic sediments of the ocean-floor, and suggested that the Dolomites in the geological past might have been atolls and barrier reefs such as now found in the South-Western Pacific.


Fig.3. The "Richthofen-Riff", a Triassic reef-compex with clinostratification (from the left to the right) into the basin sediments (St. Kassian-Fm; Wengen-Fm, mainly brown sandstones/shales/marls) by MOJSISOVICS 1879. The hard dolostone stands out from the friable shales and marls covered by meadows.

The naturally occurring cross-section in the Dolomites provided a unique possibility. It was the young geologists Edmund Mojsisovics von Mojsvar (1833-1905) who should developed further the coral-reef hypothesis, mapping the relationships between the single facies, ranging from the lagoon of the atoll to the oceanic basin. Edmund Mojsisovics von Mojsvar was a scion of an expatriated Hungarian family, he studied law, but a strong passion for the Alps led to a professional career with the Austrian Geological Survey in Vienna. Mojsisovics came to the Dolomites after establishing a biostratigraphy of Ammonites in the Austrian Northen Alps, in an attempt to correlate the various Triassic limestone-sequences in the Alps.
The detailed mapping by Mojsisovics, revealed the extent of the facies changes postulated by Richthofen, massive, generally dolomitized limestone reefs in the order of a kilometre thick passing on one side into thinbedded dasyclad-bearing lagoonal carbonates while, on the other side, they wedge out rapidly via steeply inclined foreslope beds of talus breccia into shaly and sandy basinal sediments and basalts, an order of magnitude thinner.

Fig.4. The Langkofel is composed of massive dolostone (reef-facies), suddenly falling off to the basin-sediments in the foreground (stratified St. Kassian-Fm and Wengen-Fm).

Such strong facies changes were until then considered impossible, the reconstruction of an ancient atoll landscape seemed so radical that Mojsisovics was obliged to find a private publisher for his work (MOJSISOVIC 1879).


Fig.5. Examples of slope bedding in the outer parts of the carbonate platforms of the Dolomites (after MOJSISOVIC 1879). Scheme of bedding on the flanks of carbonate platforms and examples of flank and basin deposits from the Sciliar/Schlern platform. Note the abundant limestone boulders in the basin sediments.

Fig.6. Limestone-boulders (former reef-debris), so called Cipit-Kalkblöcke interbedded in the Wengen-Fm. Encapsuled in the impermeable sediments this boulder escaped diagenesis and dolomitization.

Mojsisovics also interpreted the isolated limestone boulders of Richthofen - the so-called "Kalkstein von Cipit" - as gravity-displaced reef material that has slid down the steep outer slopes of the reefs, and became preserved in its original lithology and structure by the tight seal of shale and marl.

Bibliography:

AGASSIZ, A. (1903): Reports on the Scientific Results of the Expedition to the Tropical Pacific, the Marshall Islands. Mem. Mus. Comp. Zool. Harvard College 28: 271-329
DARWIN, C. (1837): On certain areas of elevation and subsidence in the Pacific and Indian oceans, as deduced from the study of coral formations. Proceedings of the Geological Society of London 2: 552-554
DARWIN, C. (1842): The Structure and Distribution of Coral Reefs. D. Appleton & Co., New York: 214
DARWIN, C. (1898): The Structure and Distribution of Coral Reefs. 3th edition, D. Appleton & Co., New York: 214
DARWIN, F. ed. (1887): The life and letters of Charles Darwin, including an autobiographical chapter, Volume 3. John Murray: London.
DOBBS, D. (2005) Reef Madness: Charles Darwin, Alexander Agassiz and the meaning of coral. Pantheon Books: New York
FISCHER, A.G. & GARRISON, R.E. (2009): The role of the Mediterranean region in the development of sedimentary geology: a historical overview. Sedimentology 56: 3-41
MOJSISOVIC, E.v. (1879): Die Dolomit-Riffe von Südtirol und Venetien: Beiträge zur Bildungsgeschichte der Alpen. Alfred Hölder, Vienna: 551
RISTVET, B.L. (1987): Geology and Geohydrology of Enewetak Atoll. In Devaney et al. (ed.), The Natural History of Enewetak AtollVol.1. The Ecosystem; Environments, Biotas, and Processes: U.S: Department of Energy: 37-56
SCHLAGER, W. & KEIM, L. (2009): Carbonate platforms in the Dolomites area of the Southern Alps - historic perspectives on progress in sedimentology. Sedimentology 56: 191-204

Online Resources:

BERGHAUS, H. (1892): Alpenländer geologische Karte nach v. Mojsisovics. Entw. v. Herm. Berghaus 1889, Ausg. 1890. Gest. v. A. Herrmann. Gotha: Justus Perthes (1892). Atlas der Geologie, Berghaus' Physikalischer Atlas. Justus Perthes, Gotha

Pompeii

How to teach historic events like the eruption of Mount Vesuvius in 79 A.D. ?
Why not mix history with a pop songs? Hot tip found on the Koprolitos - Blog.

Paleomammology: Body mass evolution

Fig.1. "Indricotherium" as imagined by Z. Burian in 1972 (found in SPINAR 1976).

The teeth of mammals are distinctive features; in most cases it is possible from a recovered single tooth to identify the family and often even the species. The size and kind of the tooth also helps to estimate the body weight and the life habits of its former owner.
A new database compiled with these estimated values, especially body masses, helped to reconstruct mammalian evolution since the end of the Cretaceous. The mass extinction that marks the Cretaceous-Palaeogene limit was the starting point for the increase in body mass of the mammals.
In a geological short time of 25 to 30 million years mammals increased their body weight, ranging between 3 grams to 15 kilograms during the Cretaceous, by a factor of thousand on all continents and in almost all mammalian lineages.
After the demise of large plant eating dinosaurs the newly available ecological niche was soon filled by the mammals and larger bodies were an evolutionary advantage for this replacement. Large animals lose energy in form of body-heat dispersion more slowly, have more room for large digestive organs, to handle the plants, and have fewer predators to fear. Predators on their own had to growth to catch such mighty preys.
However after this period with rapid growth stagnation took place, the largest land-mammal actually known are the herbivorous genus Paraceratherium (syn. Indricotherium), reaching 15-17 tons and living 37 million years ago in Asia, and Deinotherium, reaching 17 tons, and living 8-2 million years in Africa, marking both the acme of body size and weight of land dwelling mammals.

Fig.1. Examples of the largest and heaviest land mammals that ever lived, Paraceratherium (ca. 37-23 Ma ago), Deinotherium (8,5-2,7Ma) and the living African elephant (Loxodonta africana). The tallest on diagram, Paraceratherium, an extinct rhino relative, reached a mass of 15 tons, while Deinotherium, an extinct proboscidean, weighed as much as 17 tons. In comparison a modern elephant reaches 2 to 5 tons (figure credit Alison Boyer, Yale University).

After these giants the body mass of land mammals slightly decreased in the following periods. Comparing the fossil record to the geology and climate of the corresponding time, the research suggests also the factors that limited the evolutionary growth of mammals: the relatively warm climate delimited the dispersion of superfluous body heat, and the landmass delimited the available food resources.

Fig.2. The correlation between land size (resources) and body mass is well known, the maximum body size is determined by the number of territories that can fit into a given land area. As example the body masses of top endothermic and ectothermic carnivores and herbivores, as a function of Holocene area of landmass inhabited. Larger landmasses support larger top species, and that, for a given area of landmass, body masses decrease in the sequence (BURNESS et al. 2001).

Bibliography:

BURNESS, G.P.; DIAMOND, J. & FLANNERY, T. (2001): Dinosaurs, dragons, and dwarfs: The evolution of maximal body size. PNAS Vol. 98(25): 14518-14523
SMITH, F.A.; BOYER, A.G.; BROWN, J.H.; COSTA, D.P.; DAYAN, T. et al. (2010): The Evolution of Maximum Body Size of Terrestrial Mammals. Science 26 Vol.330 (6008): 1216-1219 DOI: 10.1126/science.1194830
SPINAR, Z.V. (1976): Quando l´uomo non c´era. Fratelli Fabbri Editori, Milano: 228

Online Resources:

SMITH, F.A. (2010): The evolution of giant mammals: Trajectory and constraints on body size over the Cenozoic. Paper No. 77-14 2010 GSA Denver Annual Meeting (31 October -3 November 2010)

24 November, 1859: New book discusses The Origin of Species

"It is no doubt the chief work of my life. It was from the first highly successful."
Darwin in his autobiography, 1876

The book On the Origin of Species, published on November 24, 1859, is an "abstract" without references, compiled by Charles Darwin from various preliminary copies.
In July 1837, only 1 year after his 5-year long voyage on the H.M.S.Beagle, the 28-year-old Darwin begun to write his first notebook on the Transmutation of Species. In October 1838 he read the book by book of Robert Malthus (1766-1834), which gave him an insight on the fierce competition acting in nature, and that slight differences along individuals could influence their destiny, and by accumulation trough time, such benevolent modifications would tend to generate new species.
In 1842 Darwin wrote out a sketch of his species theory in 35 pages, which in summer 1844 was enlarged to a work of 230 pages, both manuscripts were never finished and published posthumous. In the same year a popular book was anonymous published Vestiges of the Natural History of Creation (by the journalist Robert Chambers 1802-1871), which affirmed by observing the paleontological record that species could change over time. However the book contained wild speculations and various errors, and it was severely criticised by leading British naturalists.
This example enforced in Darwin the necessity to work on his naturalistic reputation (by studying barnacles) and also gave him the opportunity to work out review his theory and prepare to the possible criticism. He reassumed his work on the origin of species in September 1854, this time with a manuscript entitled Natural Selection-1854, it was later in the same year that a letter was delivered, coming from the distant island of Ternate in the Malay Archipelago.
Darwin realized that the sender, A.R. Wallace, who he had contacted in the past for information about animals and plants of South America, had developed a theory similar, if not identical to his own about the origin of species. Wallace's Ternate Essay and fragments from Darwin's private species manuscripts were read at the next meeting of the Linnaean Society of London and published in volume 3 of the Proceedings on August 20, 1858.
Darwin became urged to publish his theory; and so on November 24, 1859 On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life, bound in simple, green publishers´ cloth was published in 1250 copies.

Bibliography:

BROWNE. J. (2007): Darwin's Origin of Species: Books That Changed the World. Atlantic Monthly Press: 320
KUTSCHERA, U. (2009): Charles Darwin's Origin of Species, directional selection, and the evolutionary sciences today. Naturwissenschaften 96:1247-1263 DOI 10.1007/s00114-009-0603-0

How to become extinct - the Pleistocene lesson

The Funeral of Time

"Lo! trough a shadow valley,
March, with measured step and tread,
A long array of Phantoms wan
And pallid as the dead-
The white and waxen dead!
With a crown on every head
And a torch in every hand,
To fright the sheeted ghosts away,
That guard its portals night and day,
They seek the Shadow-Land."

HIRST, H.B. (1845): The coming of the Mammoth and other Poems. Phillips & Sampson, Boston.

The recognition of at least 5 major mass extinctions (excluding the recent one, where we well know the cause) in the history of life led to many speculations and hypothesis by naturalists - all sorts of geological and biological phenomena were cited as cause.
The best studied extinction events are the Permian-Triassic transition, when nearly 90% of higher life forms went extinct, the Cretaceous-Palaeogene transition, when as most recognized victims the non-avian dinosaurs disappeared, and the extinction of the Megafauna at the Pleistocene-Holocene transition.
Some of these hypotheses today sound strange: some where influenced by political and personal opinions of the respective authors, others claimed to explain all extinctions even if they dealt only with a particular event, others were very speculative and still expect acknowledgment.

Let's start with the most recent extinction event - here some theories, from intriguing to weird, which claim to explain the demise of the Mammoths and the Neanderthals at the end of the last glacial maximum.

Death from Hell - Volcanoes:

Could a catastrophic eruption modify the climate and bring death to the last survivors of a dying breed?

GOLOVANOVA, L.V.; DORONICHEV, V.B.; CLEGHORN, N.E.; KOULKOVA, M.A.; SAPELKO, T.V. & SHACKLEY, M.S. (2010): Significance of Ecological Factors in the Middle to Upper Paleolithic Transition. Current Anthropology 51 (5): 655-691 DOI: 10.1086/656185
RUBAN, D.A. (2009): A possible contribution of volcanism to the end-Pleistocene megafaunal etinction. Natura Nascosta 39:26-32

Collapse of the geomagnetic field:

Could the reversal of the geomagnetic field have deprived earth from its shield against dangerous UV-rays? A new papers proposes the increase of irridation as one of the factors contributing to the demise of the Neanderthal-man.

VALET, J.-P. & VALLADAS, H. (2010): The Laschamp-Mono lake geomagnetic events and the extinction of Neanderthal: a causal link or a coincidence? Quaternary Science Reviews Vol.29 (27-28): 3887-3893

Cosmic Impacts:

Was it a meteor or comet that devastated North America, and melted the ice-shield of Greenland, bringing a little ice-age to the globe? This hypothesis published in January 2009 raised a lot of media interest; however the idea was not supported by the chronology of the extinction of various species (ranging from various centuries to thousand of years) and later research could not replicate the discovery of impact evidence like nano-diamonds or microspheres in the sediments.

FIRESTONE et al. (2007): Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling. PNAS 105(52)

Racial demise:

The Austrian palaeontologists Othenio Abel (1875-1946) propose that the extinction of the cave bear was caused by the proliferation of a race of inferior individuals by lack of natural selection. Abel was a great palaeontologist, but with the establishment of the National Socialism in Germany he begun to sympathize with the racial pseudoscience promoted by the party, and this influenced also his hypothesis in palaeontology.

ABEL, O. & KYRLE, G. (1931): Die Drachenhöhle bei Mixnitz. Speläol. Monogr. VII - IX, Wien.
ABEL, O. (1932): La vie des animaux de l'epoque glaciare dans la Caverne des Dragons a Mixnitz, en Styrie. Terre et Vie 2: 3-24

Methane Massacre:

A research team of the University of New Mexico in Albuquerque adds a something different approach to the problem of climate change as extinction cause. SMITH et al. published a paper where they compared the production of methane of modern farm animals to extinct herbivores. Methane is a very effective green house gas. The research team observed in the geological record strong variations of the concentration of methane between the last glacial maximum, 18.000 years ago, and the Younger Dryas (13.000 years ago). Especially at the beginning of the temperature drop of the Younger Dryas the concentration of methane diminished considerable fast. The research team speculates that with the beginning extinction of large herbivores an important source of methane was removed from the climate system, destabilizing climate and environment end enforcing the extinction rate. The fast changes observed, faster than previously known variations, maybe are also related to human activity, disproving precedent research that excluded humans as triggers for the Pleistocene extinction.

SMITH, F.A.; ELLIOTT, S.M.. & YONS, K. (2010): Methane emissions from extinct megafauna. Nature Geoscience. Published online: 23. May 2010: doi:10.1038/ngeo877

Hyperdisease-hypothesis

In 2006 a research on the pathological malformations of the American Mastodon (Mammut americanum) and bison bones gave to the hypothesis developed in the fifties of a disease-related large mammal extinction new support. A large number of geographically and temporal separated individuals showed signs attributed to an infection by tuberculosis.
A recent example how lethal pathogens can be for an isolated population was observed on the Christmas Islands in the Indian Ocean. Human colonization and introduced black rats (Rattus rattus) in 1899 brougth as pathogen an unicellular parasitic protist (Trypanosoma) on the island. The endemic rat species (Rattus macleari) didn't possess a natural resistance against the introduced parasite, and the population suffered a rapid decline, in 1904 the species was considered extinct.

ROTHSCHILD, B.M. & LAUB, R. (2006): Hyperdisease in the late Pleistocene: validation of an early 20th century hypothesis. Naturwissenschaften 93:557-564
DOI 10.1007/s00114-006-0144-8
WYATT, K.B.; CAMPOS, P.F.; GILBERT, M.T.P.; KOLOKOTRONIS, S.-O.; HYNES, W.H., et al. (2008): Historical Mammal Extinction on Christmas Island (Indian Ocean) Correlates with Introduced Infectious Disease. PLoS ONE 3(11): e3602. doi:10.1371/journal.pone.0003602

The following environmental hypotheses identify climatic and subsequent environment change , and intrinsic response of the organisms, as the main causes of the mass extinction.

KOCH, P.L. & BARNOSKY, A.D. (2006): Late Quaternary Extinctions: State of the Debate. Annu. Rev. Ecol. Evol. Syst. 37: 215-250.

1. Habitat loss hypotheses

As climate changed, areas with adequate conditions to maintain megafauna either disappeared or became too small/fragmented to support populations

2. Mosaic-nutrient hypothesis

Climate change reduced growing season and plant diversity, and increased plant defenses, reducing herbivore carrying capacity and leading to extinction

3. Co-evolutionary disequilibrium

Disruption of extensive Pleistocene networks of resource partitioning by rapid glacial-interglacial transition led to extinction

4. Self-organized instability

Extinction results from a slight perturbation amplified into a catastrophe by dynamics intrinsic to complex, multicomponent ecosystems with interacting subunits

Human Overkill

The Overkill-hypotheses attribute the main extinction cause to human activity, especially hunt and habitat destruction, but also introduction of new animals and diseases.
In fact many animals got extinct when humans for the first time arrived on the respective continent; However often a large period of co-existence is observed, denying the idea of a direct "blitzkrieg" against endemic species. Archeological evidence for active and widespread hunting of large mammals like mammoths is rare, studied remains show that the most common prey were smaller animals, as the still existing bison or horse.

Fig.2. Chronology of the late Quaternary extinction, climate change, and human arrival on each continent. The timing of extinction for each genus was judged as robust or provisional based on previous publications that evaluated quality of dates. For humans, the earliest generally accepted arrival of Homo sapiens sapiens is indicated. Pre-sapiens hominins were present in Eurasia and Africa much earlier (KOCH et al 2006).

To be continued...

Supplementary Bibliography:

BUFFETAUT, E. (2004): La misteriosa fine dei dinosauri - Come le grandi estinzioni hanno modificato la vita sulla terra. Universale Storica Newton; Newton & Compton editori, Roma: 189
Introduction figure from HUTCHINSON, H.N. (1897): Extinct monsters: A popular account of some of the larger forms of ancient animal life. Chapman & Hall, ld. London.

On the Extinction of Species

The Dodo
by Hilaire Belloc

The Dodo used to walk around,
And take the sun and air.
The sun yet warms his native ground--
The Dodo is not there!

The voice which used to squawk and squeak
Is now for ever dumb--
Yet may you see his bones and beak
All in the Mu-se-um.

The possibility that species can disappear from a continent was realized 300 years ago, and only 100 years later the research by French naturalist Cuvier showed that species in fact can disappear completely - gone extinct forever.
Cuvier not only recognized extinction, but used the disappearance and appearance of fossils in the stratigraphic column of the Tertiary strata of France to divide the history of earth in various, successive faunas, every one destroyed by a revolution of the earth's surface (the chosen term to name these changes is clearly influenced by the French revolution of 1789-1799). After the catastrophic event earth got soon repopulated with new species of organisms - however this spontaneous, sudden generation wasn't addressed by Cuvier, there was a gap filled by a possible supernatural creation.
Geologist Charles Lyell, who tried to establish geology as serious science without such miraculous interference, tried to deny, and then minimize the role of these single extinction events in earth history. Lyell's hostility against extinction in general was also a consequence of his deny of organic progression (as most naturalists at these times), implying that organism, or even entire animal classes could go lost, lead to the conclusion that new species must somehow provided new, and without claiming for divine creation only a transmutation of species would be possible.
Lyell accepted a local extinction of species as consequences of climatic change, concurrence and human activity (like in the case of the Dodo), however these local extinctions were reversible, surviving animals could spread again from a refuge when the conditions were favourable again (…no species may be lost…page 193 LYELL 1842).
The apparent distinct succession of fossil faunas, so Lyell, was an artefact of former distribution of land and sea, the missing preservation of land-organisms in marine deposits and the general incompleteness of the geological record. Lyell could show that various sharp boundaries between marine and terrestrial strata, as proposed in Cuviers model of the Tertiary of France, were in fact separated by sediments deposited in lakes and rivers, there was no sudden change, but by slow rise the sea became first a swamp and later land. Also the "worldwide" limits of Cuvier ended in the Auvergne - there were no signs that this volcanic region was covered by sea in the Tertiary.
Cuvier´s Catastrophism soon became replaced by Lyell's Uniformitarianism.

Charles Darwin became strongly influenced by the geology of Lyell, observing at his first stop during the Voyage of the Beagle on the Cape Verde islands (January 16, 1832) sediments enclosed by lava flows and raised above the sea level, but with fossils similar to the shells in the sea nearby (implying no substantial change of acting natural forces and habitats over time), he applied the principles proposed by Lyell and became convinced of the slow, minute and gradual changes of earth surface.
When Darwin published his "On the Origin of Species", Catastrophism seemed long dead.
Darwin adopted his gradual change model of earth on the biological evolution of life; evolution did not need catastrophic events to explain extinction.
He stated that one of the main factors contributing to the evolution of organisms was perpetual concurrence in an overcrowded world, catastrophic events (like a drought) could occur, killing many individuals, but nevertheless this local and rare events were outstripped by the much more significant role of long-lasting, gradual natural selection, where the less adapted organism became extinct by the concurrence, and success of the modified variations.
As Lyell, Darwin considered the apparent sudden transitions of fossil faunas as an artefact of the imperfection of the geological record - in principle he denied mass extinctions as we today see it in the stratigraphic record.

But there were some theories about "evolution" and "extinction". Darwin and Wallace were both strongly influenced and based their definitive theory of 1859 also on thoughts and works of other naturalists; transmutation of species was a concept discussed at these times.
In 1831 the Scottish horticulturalist Patrick Matthew (1790-1874) published in an appendix of his book "Naval Timber and Arboriculture" a theory about transmutation in nature, which resembles the concept of variation, concurrence and selection adopted later by Darwin and Wallace:

"There is a natural law universal in nature, tending to render every reproductive being the best possibly suited to its condition…As the field of existence is limited and pre-occupied, it is only the hardier, more robust, better suited to circumstance individuals, who are able to struggle forward to maturity…"
(from RAMPINO 2010)

Matthew however, in explaining the forces that influenced this process, gave to catastrophic events a significant role, maintaining that mass extinctions were crucial to the process of evolution by eliminating concurrence, and enabling organism to radiate in the now "free world":

" ..all living things must have reduced existence so much, that an unoccupied field would be formed for new diverging ramifications of life... these remnants, in the course of time moulding and accommodating ... to the change in circumstances."
(from RAMPINO 2010)

When published, Matthew's book raised little interest, and even if both Darwin and Wallace later recognized his contribution, Matthew "evolutionary" interpretation of the geological record, with extinction events, became almost forgotten.

After "Origin of Species" the main interest of palaeontologists focused on the evolution of species, rather then their extinction.
Despite proclaiming to accept Darwin's evolution, many naturalists of the second half of the 19th century struggled with the idea of "random" natural selection (intended as a process without end destination, especially not the human species). This led to the concept of a sort of guided evolution, resembling much more the transmutation of Lamarck, where single species pass trough a development process, with generation, spreading, adaption and finally overspecializiation or degeneration, leading them to extinction. The aberrant ammonites of the Cretaceous sea and the gigantic dinosaurs were seen of such examples of overdevelopment.

Fig.2. "Aberrant" ammonites from NICHOLSON 1877, the caption of fig. 204. reads as follows: -a, Ptychoceras Emericianum, reduced-Lower Greensand; b, Baculites anceps, reduced-Chalk; c, Portion of the same, showing the folded edges of the septa; d, Crioceras cristatum, reduced-Gault; e, Scaphites œqualis, natural size-Chalk; f, Hamites rotundus, restored-Gault.

The idea of a distinct extinction event acting worldwide, and then forcing evolution, remained a neglected theory for the rest of the 19th century, and most of the 20th century, even when large scale geological changes, as for example an ice-age, were accepted in the scientific community.
Maybe the idea that terrestrial phenomena could endanger life on earth seemed to threatening? It was so that an extraterrestrial phenomenon brought the role of catastrophes in earth's evolution back to discussion.

A last question remains: what if Darwin had to explain to the Dodo what´s extinction about...

Bibliography:

BUFFETAUT, E. (2004): La misteriosa fine dei dinosauri - Come le grandi estinzioni hanno modificato la vita sulla terra. Universale Storica Newton; Newton & Compton editori, Roma: 189
DARWIN. C. (1872): On the Origin of Species by means of Natural Selection. 6th Edition. John Murray - London
LYELL, C. (1842): Principles of Geology: or, the Modern Changes of the Earth and its Inhabitants, considered as illustrative Geology. Volume III. Hillard, Gray & Co., Boston: 476
NICHOLSON, H.A.(1877): The ancient Life-history of the Earth - A comprehensive outline of the principles and leading facts of palaeontological science. William Blackwood and Sons, Edinburgh-London: 407
RAMPINO, M.R. (2010): Darwin's error? Patrick Matthew and the catastrophic nature of the geologic record. Historical Biology, 2010; DOI:10.1080/08912963.2010.523948
ROTHSCHILD, W. (1907): Extinct Birds. Hutchinson & Co. - London: 244 + 45 plates - Figure of Didus cuccullatus taken from this book

Online Resources:

New York University (09.11.2010): Scottish Horticulturalist Patrick Matthew Proposed More Accurate Theory of Gradual Evolution Before Charles Darwin Did, Geologist Argues. (Accessed 21.11.2010)

Ibexes as outstanding climbers and improvised geologists

The Alpine Ibexes (Capra ibex) living near the artificial reservoir in the Bremba-valley, situated at 2.142m above sea level in the Orobic Alps (Lombardy) in Italy, can be observed to gather around and then climb the steep wall of the dam, constructed by an electric company in 1933 to dam the river Brembo.

The animals are searching for the natural mineral deposit that this place can provide - rocks inserted on the concrete surface of the 50m high wall and containing precious minerals, at least from the prospect of an ibex.
The water from the reservoir is slowly percolating trough the wall and the rocks, and evaporating on the surface it deposits a layer of various salts and minerals. It's these natural resources that the animals are exploiting (and licking), and their outstanding climb-abilities and anatomical features enable them to reach even the most exposed point on the dam.

Fig.1. and 2. Even the young ibexes dare to climb the wall, following the example of older and experienced individuals. The hard hoofs of the animals enable them to balance on the projecting rock, and the soft pads act as excellent grip surface, Photos by Adriano Migliorati/Caters News/National Geographic Italia.

Fig.3. Two geologists (recognizable by the use of a hammer) examining a rock face in the Alps, accompanied by their guides: from the frontispiece of Natural-historical Alpine Travels (1830) by the Swiss geologist Franz Joseph Hugi (1796-1855). This illustrates the kind of fieldwork being undertaken by geologists in mountain regions (note the similarities to the previous pictures).

Bibliography:
MAINARDI, D. & BURGIO, F. (2010): Lo stambecco equilibrista. OASIS N°.190/ Ottobre-Novembre 2010: 20-21

Nyamuragira and Nyiragongo: History of two dangerous volcanoes

Many active, dormant and extinct African volcanoes are like the pearls of a necklace located along the Great Rift Valley, an active rift which almost splits Africa in half.

It's in the mid position of this rift-system, near lake Kivu, that the most active and dangerous African volcanoes can be found, the Nyiragongo (3.469m) and the Nyamuragira (3.085m). The Nyamuragira erupted between 1894 and 1979 for fifteen times (and is still active) forming large lava-streams (well recognizable on satellite imagines), however not affecing a densely populated area. In contrast the last eruption of the Nyiragongo in the Democratic Republic of Congo in January 2002 killed more than 100 people and caused great havoc in the nearby city of Goma - a foreseen catastrophe.

Fig.1. Igneous provinces of the Great Rift Valley (modified after U.S. Geological Survey, 2002).

The Nyiragongo, or mother of Gongo, after a spirit said to be living on the mountain, became famous for the lava lake in his 400m deep crater that persisted from 1927 until 1977. In 1958 an expedition by the Centre National Volcanologique Belge explored the lake, and after bypassing two platforms of solidified lava, the former surface of the lake, they analyzed the petrological composition of the peculiar basaltic lava, characterized by the presence of Leucite and Nepheline (minerals that from in lava with low silica-value) and measured a temperature of 1025-1095°C.

Fig.2. Simplified geological map with main lava-streams (name/year of formation from historic events) of the region of Nyamuragira (lava-deposits of this volcano yellow-orange) and Nyiragongo (blue-violet-red) projected on a satellite imagine (modified after PICHLER 2007, satellite imagine acquired in December 11, 2001 by NASA).

In 1964 the lava lake slowly begun to rise, and on January 10, 1977 a fissure opened on the flanks of the volcano. The very fluid lava reached a velocity of 15 to 60km/h, many villages were destroyed and on the street to the city of Goma the lava flow overtook and killed a group of peasants. The estimated number of victims ranges from a minimum of 72 to some hundred killed people.

After the eruption the volcanologist Maurice Krafft discovered in the solidified lava on the flanks of the Nyiragongo large hollows. After breaking apart some of them it was discovered that these hollows were the moulds of elephants and humans, killed and engulfed by the lava.

Fig.3. Mould and bones of an elephant, photo taken by Maurice Krafft after the eruption of 1977 (KRAFFT 1990, this image is taken from DECKER & DECKER 1992). The very fluid lava (with low silica content) killed and engulfed a small herd of elephants.

On June 21, 1982 a new lava lake begun to form in the crater and after three months it reached a level of 400m above the former ground. Until 2001 this new lake experienced various fluctuations, and between June and October 1982 the volcanic activity increased, despite this the eruption affected only the inside of the crater, until 2002.

In 2001 the high lake level aroused preoccupation, and it was expected that like before the flanks of the mountain would collapse - in January 2002 a new fissure opened near the old ones, diverging the lava in direction of the airport and the city of Goma.
The city was caught unprepared, and thousands of inhabitants fled in panic, it wasn't even attempted to diverge the lava flows by earth-dams.
The missing political awareness, the fail of mitigation measurements and the missing monitoring program of such a dangerous volcano, practically inexistent since 1985, led to this avoidably catastrophe, and is unfortunately a direct result of the chaotic political situation in this part of Africa.

Bibliography:

DECKER, R. & DECKER, B. (1992): Vulkane. W.H. Freeman & Company, New York - Oxford: 267
KRAFFT, M. (1990): Führer zu den Virunga-Vulkanen. Enke-Verlag, Stuttgart: 187
PICHLER, T. (2007): Vulkangebiete der Erde. Spektrum Akademischer Verlag, München: 261

Quantifying the importance of glaciers discharge for humans

Monitoring of glaciers worldwide has shown that almost all of them experienced considerable loss of volume in the last century, and especially the last decades. And for the next future there is no sudden turn to be expected.
This raised some concern, especially considering the role that glaciers have in the hydrologic circle of mountain ranges. Glaciers act as storage; they collect and hold back precipitation during winter, and release it during spring and summer, smoothing the average discharge of a catchment area.

Common scenario's stated that the melting of glaciers would diminish the amount of water for agriculture use, and also potable water, causing droughts that could influence up to 2 billion people (mainly Himalaya-area and China). However such statements are inferred often only by considering the human population in a certain catchment area, and thus overestimated.
The importance of glaciers for humans however depends on various climatic and geographic variables. Not only matters how much people live in a catchment area, but also when glaciers release the stored water in relation to the annual precipitation.

In the Himalaya the main discharge occurs during spring and summer, when anyway the monsoon brings great amounts of water. The impact of reduced glacier discharge in this example on humans is therefore low.

In contrast in the region of the Aral Sea the main precipitation peak is during winter, and the glaciers release the water during summer drought. Here the role of glaciers for local communities is essential.

These first results will help to put the discharge reduction in the correct regional scale, point out regions were this discharge shortage can became a major problem and where mitigation strategies must be considered in the future.

Fig.1. The map by KASER et al. 2010 (click to enlarge) summarizes the results for the various analysed catchment areas with glaciers, the grey bars represent the Population Impact Factor, a factor that encompass the amount and time when glaciers contribute to the demand of population in relation to the annual precipitation.
High grey bars shows that glaciers provide water when it is needed most, low bars shows that the discharge of glaciers occurs during wet periods, when their contribution is less important.

Bibliography:

KASER, G.; GROßHAUSER, M. & MARZEION, B. (2010): Contribution potential of glaciers to water availability in different climate regimes. PNAS November 8, 2010; Published online before print DOI: 10.1073/pnas.1008162107

Discovering the Lost World: The use of primordial prehistory in movies

The "Lost World" plays a major role in many movies featuring prehistoric monsters, movies that can be attributed to various genres, like fantasy, science-fiction or horror, but are tied together by this characteristic element.

The Lost World is not a coincidence in all these different movies, but a crucial part of a good story. First let's shortly consider what a Lost World can be, there are various variations of this story element, even if they all share some common properties.

The "Lost World" as isolated part of our world

The idea of survival of prehistoric monsters in isolated regions of the world was created in the appropriately named novel by Arthur Conan Doyle "The Lost World" in 1912. It's the classical Lost World, made to a movie in 1925 (The Lost World, U.S.A.), a remote region in the Amazonian forest, delimitated by steep cliffs and mountains, isolated from the rest of the world and so hidden, that even time forgot this land. This Lost World is used widely in later movies, with minor variations - remember the various "King Kong" (1933) versions (and copies), with remote islands or jungles, "The valley of Gwangi" (1969), with a lost valley, "The Land Unknown" (1957) and "Land that Time forgot" (1975) , also "The last Dinosaur" (1977) - where the prehistoric land is isolated by the ice of Antarctica from the rest of the world.
Jules Verne located his Lost World in the centre of the earth (1864 "A Journey to the Center of the Earth"), theme adopted by the novel based U.S. movie of 1959 "Journey to the Center of the Earth", and reused in "At The Earths Core" (1976).


An advantage of this kinds of Lost World is the apparent possibility to gather creatures of all kind of time periods, the classic dinosaur's encounters cave men situation.

Modern videogames (like the Turok series) locate the Lost World in outer space, some movies used distant planets, like "Planet Of The Dinosaurs" of 1978, or a comet, see for example "On a comet", a 1970 Czech film based on a novel by J. Verne, despite the improbability of the same (or very similar) evolutionary path like earth, here dinosaurs did not or did not yet go extinct.
The Russian film "Planeta Bur" ("Storm Planet", 1962) is about an expedition to Venus that discovers dinosaurs. The film exists in many recut versions, including "Voyage to the Prehistoric Planet" and "Voyage to the Planet of Prehistoric Women".
Also a plausible location (at least for a science-fiction movie) is a parallel dimensions or an alternative reality ("Adventures in Dinosaur City", 1992), where time and evolution developed other than by us.

The man made "Lost Word"

A modern, to the scientific advance adapted version of the isolated Lost World was introduced by the novel of Michael Crichton "Dino Park" (1990), where a remote, however inconspicuously Island is populated by genetically recreated dinosaurs. Here a Lost World is created artificially, theme readopted in the sequels ("Lost World" 1995 and "Jurassic Park III" 2001), however in the latter cases with elements that made it more naturally - the dinosaurs are left alone on the islands and begin to evolve.
Also a modern variation of the genetically created population is the time travel created population, where by time travel technology creatures of the past are brought to the present to live on a modern Lost World (used in the video games series "Dino Crisis" 1999). This new introduced element leads us to the next general versions of Lost Lands.

The "World lost in Time"

Here the Lost World is not so much a foreign element, because in fact it is located in its correct time.
However two possible subgenres can be differentiated, in the first we experience the adventures of time appropriated heroes, like dinosaurs or cave men, in the second one modern people use time travel technology to enter this world, like spatial barriers, here temporal barriers have to be overcome.
It must be said that the scientific and temporal accuracy of this Lost World mostly is reduced on a summarized, general past, where dinosaurs, mammoths and cave men, sometimes even ancient civilizations, live together.
One of the first examples of this kind is the U.S. production "Brute Force" in 1913, where also the dinosaur as bloodthirsty monster is introduced in the movie world, one of the most popular movies is "One Million Years B.C." (United Kingdom,1966). Other examples include "When Dinosaurs ruled the Earth" (1970) and "The Creatures the World forgot" (1971), and "Slave Girls" (!!) (1967) clearly shameless ripp-offs from the original.


The second subgenre is again more used in video games, where the heroes fight they way trough prehistory to return in their time, or vice versa like in "Journey to the Beginning of Time" (U.S./Czech production of 1955). An intriguing modification of this time-traveller approach is the post apocalyptic world in which extinct monsters got revived and clash with human survivors, like in the B(ad)-movie "Yor".

Bringing the "Lost Word" to our world

A modification of the Lost World theme is to let survive from the past only single elements, like an individual dinosaur entrapped in ice or remains (bones, tissue) of a prehistoric creature conserved in the sediments. The first idea was used in classic monster movies like "The Beast from 20,000 Fathoms" (U.S.A. 1953), "Godzilla" (Gojira, Japan 1954), "Dinosaurus!" (1960), the second idea, a prehistoric monster reborn by self-regenerating tissue from a borehole, is realized in a shlock masterpiece "Reptilicus" (Danish-U.S.A. production of 1961).


In all this variations the Lost World is an important element to tell the story, it's a stage were the drama is performed, but a particular one.
The Lost world is, said it simplified, a version of the haunted mansion, a classical element of a historic horror story. The Lost world itself is threatening, strange creatures lurk in it, animals but also men-eating plants, even elements of the landscape, like quick sand or rock fall, are deadly traps.

The spatial and temporal barriers, so often emphasized in these stories, have two effects, first they provide a rational explanation for this world, and why we never heard about it, second they act as point of no return, as slippery ground, once trespassed the wall that separated the humans of the reign of King Kong, the monsters get loose, the hero can't turn back and the story develops to its acme.
To make this world even more real for the spectator, by explaining it in a rational manner, to guide us trough this world is a scientist, who also knows the weak point of the monsters, and, if not self involved in the battle, helps our athletic hero to fight the beasts.

The jungle or caves of the Lost World confines not only the space where the story and hero acts, but gives at the same time the classical opponent (dinosaur, monster) both possibilities for a direct attack and hidden attacks - for example the dense vegetation of a jungle provides a lot of places to hide for the monster, from where it can suddenly jump out and attack. The danger in such a three-dimensional world can come from every directions, as example in many stories not only land dwelling dinosaurs attacks, but also flying pterodactyls.

Perpetual pressure is acting on the hero (and tension on the spectator), confining the space, with danger all around; the hero is entrapped and can't get help from outside.

The Lost world has another advantage in regard to other confined places (like a spaceship, see "Alien" 1979), the jungle can host a variety of creatures, various opponents can attack in short intervals, without appearing repetitive, in fact many bad monster movies after the first attack reduce the plot to a repeated repetition of the same attack techniques.

Another element in such stories is the use (or misuse) of evolution, which I will try to address in a second post.

Bibliography:

DALLA VECCHIA, F.M. & MARRA, A.C. (2006): Dinosauri di celluloide: una filmografia ragionata. PaleoItalia 15 Novembre 2006: 16-23
TRUBY, J. (2010): Horror, Fantasy and Science Fiction. Truby's Video & Audio Classes 2010