Will democracy survive climate change? - A lesson from the past

Allegory of volcanism as bringer of fortune (fertile soils) and destruction, by artist Alexandre-Évariste Fragonard (1780-1850) after a draft by French naturalist Joseph Nicolas Nicollet (1786-1843).

In June 1783 a volcano in Iceland erupted. Volcanoes are nothing unusual in Iceland, but this eruption, later referred as Laki,  was different. For eight months volcanic ash and gases poisoned the atmosphere over Europe changing the climate for years to come. In Europe the exceptionally hot summer of 1783 was followed by long and harsh winters until 1788. Crop harvests were poor and bread, essential for the large and poor population on the continent, experienced a massive price increase.

Map showing the lava flows of Lakagigar, from Magnus Stephensen "Kort Beskrivelse: Vester-Skaptefields-Syssel paa Island" (1785). The lava from the fissures ended up covering an estimated 2,500 km² (965 sq mi) of land.
 

At the time France was characterized by a great inequality between the poor peasants and the upper class. The rich aristocracy and the corrupted clergy lived in an own world, distant from daily problems. The lower and middle class had no political power despite its important role in economy and the king was to weak to control the aristocracy. Poor harvests and war expenditures resulted in an economic crisis and famine spread. In human history hunger was always a powerful agent of change. Italian officials noted in 1648 during a widespread famine that “it was always better to die by the sword than to die of hunger.” Women revolted on the streets demanding bread. July 14, 1789 5,000 citizens of Paris stormed the Bastille. Years of chaos followed. French lawyer Maximilien Robespierre instituted an authoritarian regime, culminating in 1793 with the execution of king Ludwig XVI. followed by 16.000 other people only in Paris. In 1799 Napoleon Bonaparte promised to bring order in those chaotic times and in the end declared himself emperor - celebrated by the same people that just some years earlier battled an absolute monarch. Even if the French Revolution is often seen as starting point for the modern Europe, democracy was predated by tyranny.

Georg Heinrich Sieveking’s “Execution of Louis XVI” in 1793.
 

Today we observe similar tumultuous times and a changing climate. However this time the changing climate is not the result of a short-lived volcanic aftermath. The warming caused by the anthropogenic carbon-dioxide emissions  into earth´s atmosphere will continue for the next centuries. Some research has suggested that a warmer climate will fuel future conflicts. Droughts can cause water and food shortages in less industrialized nations. In 2010 drought in Russia and too wet weather in Europa caused a 20% loss of crops harvest, prices in response were raised on the international market by 40 to 70%, also due speculations. China, also suffering from a poor harvest, stocked crop, causing ulterior shortages.

The increased costs, widespread unemployment and misery lead to riots and demonstrations in many North African countries. The chaos lead in part to installments of  governments controlled by the military and in Syria (hit also by a drought from 2006 to 2010) the civil war is still going on. The civil wars in Africa and Near East caused mass migrations of refugees to the first world countries, Europe was not ready for the onrush, causing a political chaos. In response many right-winged parties, promising simple solutions like walls or travel bans, gained support in many European countries (U.K., France, Germany, Austria, Italy). Right-wing politics promised also simple solutions in the United States. The poor and middle class fears migration as this implies to share already limited resources. The rich class supports such fears as it distracts from the real causes (less than 3% of the population controls more than 50% of the global wealth).
Travel bans and suppressing research about climate change doesn´t solve problems but simply hides the truth. Already authoritarian systems like Russia or China seem also best fitted to deal with future climate change. Such systems can suppress disadvantageous news about climate change effects but also react faster to impending disasters. China, dealing with severe environmental problems due its rapid industrialization, planted millions of trees in governmental controlled projects or simply limited traffic in cities. Such projects would need more effort, time and especially support by citizens in democratic systems.
In times of supposed chaos, overwhelmed by the problems (real or faked), we demand for simple solutions, as authoritarian systems can quickly promise (if they really will hold the promise is another problem), but simple is not necessary the right way.

Non Sequitur by Wiley Miller

January 6, 1912: Happy Birthday Continental Drift!

January 6, 1912 the German meteorologist Alfred Wegener presented in a lecture entitled “Die Heraushebung der Großformen der Erdrinde (Kontinente und Ozeane) auf geophysikalischer Grundlage” (The uprising of large features of earth’s crust (Continents and Oceans) on geophysical basis) for the first time his hypothesis of the ancient supercontinent Pangaea, from which all modern continents split apart.
Three years later he will publish his book “Entstehung der Kontinente und Ozeane“, translated in the third edition and published in 1922 as “The origin of continents and oceans.”
 

Wegener didn’t propose something completely new; as he based his idea on earlier observations and suggestions, but his work started a fierce discussion in the scientific community.

  

In 1889 and 1909 the Italian musician and naturalist Roberto Mantovani published a hypothesis based on his observations on the volcanic island of Réunion: cracks forming during volcanic eruptions could separate even large parts of an island, could it then be possible that entire continents split apart? Mantovani collected various evidence and published maps to show the shape of the hypothetical former continents (Wegener will use these maps to support his idea), however he explained the driving force behind the breakup of former large continents by the slow expansion of the earth.
 

In 1908 the self-educated geologist Frank B. Taylor proposed that the crust of earth was influenced by tidal forces of the moon and the continents were pulled apart in some regions and pushed together in other areas, forming folds like a carpet. However the involved forces were to weak and his explanation wasn’t deemed plausible. The Austrian geologist Otto Ampferer speculated in 1906 that the Alps were formed by folding of the upper crust, as driving force he proposed magma sinking into the mantle and pulling pieces of crust downwards (!). This “Unterströmungstheorie (also Subfluenztheorie)” lacked however a convincing source of energy and couldn’t explain all aspects of the genesis of the Alps, as it implied only pulling and not compressive forces needed to form folds and faults.

Wegener became interested in the idea of a single continent in 1910 by observing an atlas and noting the coasts of the Africa and South American. Some time later he read a paleontological paper discussing the similarities of terrestrial fossils between separated continents.
 
Wegener continued to collect various published evidence to support his theory of a single continent:
- Like a puzzle also the outlines of continents (especially the continental shelves) seem to fit together.
- There are various geomorphologic and geological similarities along the coasts of South America-Africa and Europe-North America.
- Fossil of land vertebrates and plants can be found on different continents, separated today by large oceans.
- Fossil evidence of ancient climates, today without a recognizable pattern, will form climate zones when the continents are put together.

Wegner considered the prevailing explanation for the patterns in the fossil record as impossible: ancient land bridges that connected continents and habitats (like the Isthmus of Panama today) were composed of light continental granitic crust, such pieces of less dense rocks couldn’t simply sink into the much denser oceanic basalts and disappear without trace.

He will explain in 1911 his idea in a letter to his father-in-law, Professor Wladimir Peter Köppen:

“You consider my primordial continent to be a figment of my imagination, but it is only a question of the interpretation of observations. I came to the idea on the grounds of the matching coastlines, but the proof must come from the geological observations.
These compel us to infer, for example, a land connection between South America and Africa. This can be explained in two ways: the sinking of a connecting continent or separation. Previously, because of the unproven concept of permanence, people have considered only the former and have ignored the latter possibility. But the modern teaching of isostasy and more generally our current geophysical ideas oppose the sinking of a continent because it is lighter than the material on which it rests. Thus we are forced to consider the alternative interpretation. And if we now find many surprising simplifications and can begin at last to make real sense of an entire mass of geological data, why should we delay in throwing the old concept overboard?“

 

  

Wegener hypothesis of continental drift (a catchy phrase adopted mainly by the critics, as Wegener talks more general of “displacement theory“) was received with mixed feelings. Most geologists regarded it as cherry-picking of anecdotes from the literature. However some geologist with field experience, especially in Africa and South-America, became soon convinced of this possibility.

Like Taylor also Wegener could not explain the forces necessary to move the continents in the crust. Wegener imagined that continents - like gigantic ice floes - swim on and are surrounded by the much denser oceanic crust.  He proposed gravitational pull, tidal and centrifugal forces, but the English geophysicist Harold Jeffreys demonstrated that these forces are much too weak or if strong enough, had to stop first earth’s rotation.
 
Wegner himself reacted to the critics and tried to respond to them in various editions of his books, however with moderate success. The greatest problem remained the lack of direct evidence for the movements of continents and the needed explanation for the mechanism and also the large amount of energy needed to move and deform rocks. Most importantly Wegener considered his work as starting point and stimulus for other or even future scientists, a message that wasn’t fully understand at his time.

 

Fig.1. – 3. “Eppur si muove!” Reconstruction of the former supercontinent of Pangaea and the subsequent breakup in various smaller continents from the Carboniferous to the Quaternary. From WEGENER, A. (1929): Die Entstehung der Kontinente und Ozeane. 4th ed.

Wegener will die in 1930. His continental drift hypothesis is in many aspects erroneous: not the single continents move but entire plates of the crust and the driving force comes from within the planet, not from outside. However his most important legacy is to have introduced the idea of moving continents to the scientific community and the public (even Lovecraft will became inspired by Wegener’s writings) – decades later this legacy will influence a new kind of theory: Plate Tectonics.

Bibliography:

MILLER, R. & ATWATER, T. (1983): Continents in Collision. Time-life books, Amsterdam: 176
SCALERA, G. (2003): Roberto Mantovani an Italian defender of the continental drift and planetary expansion. From Scalera, G. and Jacob, K.-H. (eds.): Why expanding Earth? – A book in honour of O.C. Hilgenberg. INGV, Rome: 71-74

How the Study of Plants revealed the Variability of Climate

The news of the resuscitated "Ice Age plant", regenerated from 30.000 year old tissue conserved in permafrost, is an intriguing discovery that will help to better understand the evolution of ecosystems during one of the most dramatic epochs of earth history - the Pleistocene-Holocene transition some 10.000 years ago, characterized by strong climatic oscillations from glacial to interglacial conditions.

Already the study of fossil plants played an important role in the reconstruction of the environment and the climate of this period.  The German explorer Alexander von Humboldt (1769-1859) was one of the first naturalists to scientifically discuss the distribution of plants related to environmental factors like temperature, rainfall, latitude, height and soil - one of the most famous results of this work is the depiction of the vegetation belts of the Andes.

Fig.1. Vegetation zonation in the Andes, from the "Berghaus-Atlas", a supplement to Humboldt´s work "Kosmos", published in 1645-1862.

Based on these observations it became clear that the fossil remains of plants can be used to reconstruct the environmental factors during the lifetime of these plants.
In 1876 the Norwegian botanist Axel Gudbrand Blytt (1843-1898) published a book on his observations about the distribution of the Ice Age flora on the Scandinavian Peninsula. He recognized various plant communities - defined as Arctic, Subarctic, Boreal, Atlantic, Subboreal and Subatlantic - and suggested, based also on layers of peat where he observed the same plant communities in a certain order, that these communities were the results of various climate driven migrations waves on the peninsula. For Blytt especially the change of dry and wet periods controlled the distribution and migration of plants. These supposed changes could also explain the discoveries of layers with tree stumps in peats all over Europe, grown there when the climate was more favourable for trees. 

Fig.2. Blytt´s map of the distribution of plant communities in Norway, from BLYTT 1876.

The Swedish geologist Lennart von Post (1884-1951) used particular plant remains to infer past climatic oscillations. Flowering plants produce pollen grains covered by a chemically very stable substance named Sporopollenin, therefore pollen grains usually are well preserved in soils and sediments. The structures, like spikes or pores, on the surface of pollen grains are species-specific and can be used to determine from which plant-species the pollen was produced. Von Post counted and identified many hundred of pollen grains found in specific depth-intervals of sediment cores and plotted the relative percentage of every species in a diagram. He found that there was a succession of different plants; cold periods during an Ice Age were dominated by pollen from trees adapted to cold and humid conditions, like birch or pine. During warmer periods the pollen of these species disappeared and new tree species, like oak and fir, appeared in the pollen diagram. When the landscape finally became occupied by humans the amount of tree pollen decreases, as the forest is replaced with fields of grass or crop and the pollen of these plants dominate in the sediment core. 

The study of pollen, or palynology, is still today an important tool that helps to reconstruct local environment and climatic changes, the stratigraphy of recent deposits, human impact on the landscape, the rise and fall of civilizations and is even used to solve criminal cases.

Bibliography:

BLYTT, A. (1876): Essay on the Immigration of the Norwegian Flora during Alternating Rainy and Dry Periods. Alb. Cammermeyer, Christiana, Oslo, Norway: 89
HILGEN, F.J. (2010): Astronomical dating in the 19th century. Earth-Science Reviews 98: 65-80
POST, V. L. (1944): The Prospect for Pollen Analysis in the Study of the Earth´s Climate History. New Phytologist Vol. 45: 198-203

The End of the Mayan World

According to the popcorn-movie "2012" (2009) the end of the world will come due increased solar activity that will overheat earth and cause catastrophic volcanic and tectonic storms on December 21, 2012. This premise is so dumb that even NASA declared "2012" as the most "absurd science-fiction movie" of all times, not only because the science is so bad, but the movie exploits also the fear mongering story of the supposed end of the Mayan calendar, first proposed by artist and author José Argüelles in 1987. Almost all of the supposed end of the world tale is nonsense, the various proposed mechanism to explain the destruction of the planet, like solar eruptions, pole shift or the impact of an invisible planet, are unrealistic, as it is unrealistic to claim that the end of a arbitrary time period has any significance for earth.

Fig.1. The goddess Chakchell, with her terrifying snake headdress, is flooding earth with the waters coming from the jar of the gods. She is helped in this task by the dark god of the underworld, with an owl as symbol of his power, and the divine crocodile - even the holy hieroglyphs are crying and the world will soon drown (after the "Codex Dresdensis", ca. 1200-1250, plate 47 "The flood").

However in the last years the Maya Civilization arouse the interest not only of crackpots, but also serious historians and even climate scientists. This ancient society possessed advanced knowledge of astronomy, mathematics and architecture, but 1.200 years ago (750-950 A.D.) the various city-states on the Yucatan peninsula suffered a sudden collapse. Various hypotheses tried to explain this demise: internal warfare, foreign invasions, diseases, overpopulation in combination with environmental degradation and climate change.
The Yucatan peninsula is characterized by a heterogenic spatial distribution of precipitation and seasonal droughts, especially during the beginning of the year (January- May). The climate is influenced by the position of the Intertropical Convergence Zone (ITCZ), wind systems that shift position due the seasons and bring moisture to the land. The Maya had to deal with these variations and in response build large artificial reservoirs. The limestone of the Yucatan peninsula is highly permeable and the groundwater is almost inaccessible, if not by naturally occurring caves or cenotes, and there are virtually no rivers.
It was in these cenotes that geologists of the University of Florida collected sediment cores and discovered in the isotope variations of shells a pronounced drought period between 800 and 1000 A.D., coincident with the collapse of Classic Maya civilization. A even more detailed reconstruction of the climate of the region was possibly by the research done on sediments from the Cariaco Basin, a basin with limited deep water mixing and anoxic conditions on the ground (and therefore perfect sedimentation conditions) offshore Venezuela. Depending from the position of the ITCZ fossil-rich or clastic-rich layers are deposited, so by studying and counting these layers the former variation of the ITCZ and the amount of precipitation can be estimated.
Also this record shows a climate shift and cyclic multi-year droughts from 910 to 760 A.D.

According to the proposed scenario a population at the margin of environmental sustainability experienced repeated droughts and a demise of agricultural production. The various city-states, chronically involved in wars for power and sacrifice victims, consumed the last reserves in a desperate struggle for survive.

However like in the case of Easter Island considering both evidence from natural sciences and historical and cultural circumstances the scenario could become more complicated. The Mayan Civilization was characterized by religious violence and war was less aimed to destroy the enemy than to catch (and sacrifice) the political elite. This society had also survived previous droughts or phases of increased soil erosion, when in A.D. 550-830 the population reached high densities. The power became concentrated in few city-states, which struggled for power and replaced small military expeditions with great wars. The crumbling central government could no longer guarantee the safety of peasants, when the society was further weakened by climate changes.

In the end the city-states were replaced by a most decentralized kind of society, whit the descendants still living today.

Bibliography:

ANSELMETTI, F.S.; HODELL, D.A.; ARIZTEGUI, D.; BRENNER, M. & ROSENMEIER, M.F. (2007): Quantification of soil erosion rates related to ancient Maya deforestation. Geology Vol. 35(10): 915-918
GILL, R.B. (2000): The Great Maya Droughts - Water, Life, and Death. Univ. New Mexico Press: 464
PETERON, L.C. & HAUG, G.H. (2005): Climate and the Collapse of Maya Civilization. American Scientist, Vol. 93: 322-329

At the Mountains of Madness

December 14, was the 100 years anniversary of the first expedition to reach the geographic South Pole in the middle of the continent of Antarctica. Until then only segments of the coasts were known and partially mapped.  

Fig.1. The dog Chris inspecting a grammophone during the Scott Expedition in Antarctica  (photo by Herbert George Ponting, 1911).

It is no wonder that such an unknown land influenced the imagination of many writers and later film directors. 

"At the Mountains of Madness" is a science-fiction/horror story by the American writer H. P. Lovecraft (1890-1937), written in February/March 1931 and originally published in three parts in the February, March and April 1936 issues of the pulp-magazine "Astounding Stories" (also one of the first pulp- and horror fiction magazines ever to be published).
The story is written in a first-person perspective by geologist William Dyer, a professor from Miskatonic University, which led a geological expedition to Antarctica in "1930".
The expedition discovers first strange fossils, eons of years older then all other signs of life on our planet, and finally a mountain range, much higher and darker then ever imagined. But after a carefully investigation along the borders of the mountains and the discovery of even more strange fossils, contact get lost with a part of the team and the narrator makes his way to discover what happened at the Mountains of Madness.
Lovecraft incorporates in his story many scientific observations made at the time, especially the discovery of fossils. Little was known about the geology of Antarctica; rock exposures comprise only 1-3% of the land area and are limited to isolated coastal regions and to the peaks of the Transantarctic Mountains, crossed for the first time by the Ernest Shackleton-expedition in 1908. Only in 1928-1930 the Richard Evelyn Byrd-expedition collected the first fossils.
Still today sites with fossils are rare spots; from Antarctica we know some dinosaur species, synapsid species, a plesiosaur, Eocene mammals and a terror bird - however plant remains are by far the most common fossils and especially these plants proofed that Antarctica was once a tropical paradise.
Lovecraft describes the fictional discovery of a cave that acted as sediment trap for millions of years:

"Washed down from unknown jungles of Mesozoic tree ferns and fungi, and forests of Tertiary cycads, fan palms, and primitive angiosperms, this osseous medley contained representatives of more Cretaceous, Eocene, and other animal species than the greatest paleontologist could have counted or classified in a year."

Also other authors located a tropical Lost World near the Antarctic continent. Edgar Rice Burroughs (1875-1950) published in 1918 the first part of a science-fiction book in the "Blue Book Magazine": "The Land That Time Forgot". Here a primordial world populated by tropical forests and of course dinosaurs is located on the island of Caprona, a land mass near Antarctica, first reported by the (fictitious) Italian explorer Caproni in 1721. The tale inspired two movies: "The Land That Time Forgot"(1975) and "The People That Time Forgot"(1977).

Fig.3. Cover art for first combined edition (1924) of The Land That Time Forgot.

The Younger Dryas impact hypothesis

The cause(s) that led to the extinction of most of the larger mammals that roamed the Pleistocene world are still today unknown. Many different hypotheses were proposed, from human overkill to climate change, but more unusual was an idea largely publicized in 2007.

Geophysical studies presented in spring 2007 suggested that perhaps an extraterrestrial bolide vaporized in the Earth's atmosphere caused the extinction of the North American Megafauna some 13.000 years ago.
In 2009 this hypothesis seemed to be further confirmed by subsequent findings. This and other interdisciplinary research presented various sedimentological features found in peat layers at nine excavated sites of the North American continent and one site in Belgium and thought to be associated with impacts of meteorites on earth.

Fig.1. Profiles of sites in North America with proposed sedimentological evidences for an impact event some 12.900 years ago. The diagrams show the concentration of magnetic particles, microspheres, particles of coal and glass and some elements rare in the earth's crust but common in meteorites (such as iridium, chromium and nickel). The highest values are apparently found in a distinct single thin layer, after FIRESTONE et al. 2007.

1) An increased concentration of iridium, a rare element in earth's crust but common in meteorites.

2) Metallic particles and grains, also carbon microspheres concentrated in a thin layer, interpreted as remains of the impacted meteorite and the recrystallized molten rocks of the bolide and crust.

Fig.2. and 3. The metallic micrometeorites with a diameter between 100 to 150 µm found in one of the profiles (Blackwater Draw) showed a high content of titanium and nickel typical for extraterrestrial material (FIRESTONE et al. 2007), also shown the carbon microspheres interpretated as the remains of the molten and recrystallized bolide.

3) A particular and rare modification of carbon - Lonsdaleite - in shape of microscopic nanodiamonds with a hexagonal crystalline structure formed only under very high pressure as experienced during an impact.

4) Another exotic modification of carbon, the Buckminsterfullerene or buckyballs, a modification of carbon that supposedly can be created only under great heat conditions.

5) Dark layers of peat or sediments rich in organic matter were interpreted as the remains of burned vegetation by megafires ignited by the heat of the impact.

6) Recovered Pleistocene bones of mammoth and bison showed features that were interpreted as direct effects of the explosion - small, 2 to 3 mm in diameter, holes in the bones with a burned halo and penetrated magnetic particles with a high content of iron and nickel of unusual isotopic composition.

To explain the lack of the most compelling evidence - the impact crater- it was suggested that the bolide exploded above or on the Laurentide ice shield, leaving behind no visible trace.
7) An alternative suggestion positioned a debris field in the Carolina Bay area along the south-eastern coast of the United States. The Carolina Bays include thousands of circular to elliptical depressions across the coastal plain of still unknown origin (some authors suggested even spawning fish).

The most intriguing conclusion of the Younger Dryas impact hypothesis: The heat released and the shock waves of the impact caused the extinction of the North American Megafauna and the annihilation of the Clovis-culture possibly in two ways, by directly killing animals and igniting large scale firestorms and in a second moment by the partial melting of the ice shield of North America and Greenland. The large amounts of fresh water released in the Atlantic Ocean caused an arrestment or a slowdown of the warm Gulf Stream, starting a 1.500 years long climatic reversal recognized especially in Europe as Younger Dryas stadial (12.900-11.600 cal BP), an important phase of cooling recognized in glacier advances and vegetation shift.

Fig.4. The isotopic values as proxy of climate recovered in ice cores from Greenland show a distinct phase of climatic reversal between 12.900 and 11.600 years ago. The sudden beginning of this period named Younger Dryas stadial is still poorly understand, the influence of changing patterns of the marine currents in the Atlantic at the end of the Pleistocene are the most suggested and likely triggers of such an abrupt climate change (Greenland Ice Core Chronology 2005 released 10. March 2006).

The hypothesis experienced a positive and large attention in the popular media but got mixed reception from earth scientists during it´s official presentation in May 2007 at the congress of the American Geophysical Union.
The meteorite idea was however not completely new and already published in 2001 and in 2006 even in a own book - however with some pseudoscientific implications like glacial landscapes with drumlins or the North American Great Lakes as the direct results of the impact.

Also focusing only on the research published in 2007 soon problems arouse. For example the methods used to identify some of the most compelling impact evidence, like the nanodiamonds, were questioned because the results of the analyses were explainable also by other, more earthly, materials.
More important - the impact hypothesis could only explain a local decline and extinction event for the American continent in a very short interval, maybe in few decades or centuries. However dated fossils seem not to support a unique and sudden extinction as proposed by this and many other catastrophist hypotheses. In a survey on 4.532 archaeological sites in Europe and Siberia and 1.177 dated remains of mammoth and mastodons in Europe, Siberia and North America the dates scatter between 45.000 to 12.000 years.
Estimating the development of the population of single species there seems to be various phases of increase and decline in numbers of individuals. The woolly mammoth for example reaches a population maximum some 16.000 to 15.500 years ago, this phase is followed by a slow decline 14.500 to 13.500 years ago, however isolated populations survived on islands and in northern regions of Asia even until historic times.

Apart of these general critics in 2011 a paper By PINTER et al. focused explicit on the single evidences as presented in 2007 and subsequent years and concluded that most of the claims can not be reproduced and the few reproduced evidences are not unequivocally related to an impact of an extraterrestrial bolide:

1) The iridium concentration was not measured in the bulk sediment but on single fragments or spherules thought to be of impact origin - this could falsify the apparent peak in the stratigraphic column. On some studied sites the concentration of iridium in the supposed Dryas interval was also surprisingly low. Despite the methodological error, these contradicting results are imputable to diagenetic alteration of the sediments and the iridium concentration is more likely of terrestrial origin.
More notable subsequent research failed to reproduce the single iridium peak.

2) Some of the carbon spherules resulted to be fungal spores or coprolites of arthropods. Subsequent research could not reproduce a peak or concentration of micrometeorites in a single layer, but the particles resulted to be distributed homogenous in the stratigraphic column, as more likely explained by the common background sedimentation from the interplanetary space occurring during geological times.

3) The supposed nanodiamonds resulted by further and more detailed investigations to be amorphous to polycrystalline carbon aggregates as produced during common wildfires, the presence of the particular carbon modification Lonsdaleite could not unequivocally proven in the sediments.

4) The presence of buckyballs was questioned because of methodological problems already in the original research and later investigations could not reproduce the results. Despite the dubious presence of the fullerenes, it is known that small amounts of this carbon modification can be produced by common wildfires, so even if buckyballs will be found, these are not unequivocally evidence of an impact.

5) Sediments rich of organic matter are not necessary produced by wildfires; common depositional environments like swamps can also produce thick layers with encoaled plant remains. Some proposed impact-related dark layers, supposedly rich of organic matter, resulted even to be coloured not by organic remains but by minerals. There is today no unequivocally evidence that the layers are connected to any wildfires after an impact.

6) Some of the bones with the supposed fragments of the bolide resulted to be older by nearly 20.000 years than the previously specified impact date. The fragments in the bones were not reanalyzed after the first claims and doubts arouse of the proposed origin.
It seems unlikely that such minuscule and fragile particles could penetrate earth's atmosphere and still impact on such a hard material as are the bones. In alternative it is well possible that the discovered particles are more likely diagenetic iron concentrations.

7) The explanation of the Carolina Bays as debris field is not supported by any discovery of extraterrestrial material in the area; also relative dating efforts showed that these depressions were formed probably during a long time interval. So if these features still remain mysterious an impact origin seems the most unlikely cause of origin.
Even radiocarbon ages achieved by the impact supporters showed significant fluctuations in the ages of formation, ranging from 6.500 to 700 years ago. This lead to the excuse that "the impacting object was ejected by a recent near-Earth supernova in which case carbon [was] enriched" modifying the radiocarbon age of the sediments.
Realizing the improbability and problems of such claims the Carolina Bays were rejected as evidence by most impact proponents.

The Younger Dryas Impact Hypothesis was adopted mainly by non earth-sciences related researchers and especially the mass media, who dedicated to the scenario even various TV-shows. Even if it was stated that some of the results were preliminary, it is still surprising how catastrophic theories are accepted uncritically by popular media.
However three years later it seems that most of the proposed evidence for the Younger Dryas Impact Hypothesis could not be reproduced by other teams and were evidence is available there are terrestrial, non impact related, interpretations possible.

Bibliography:

BECKER (2007): Abstract: The End Pleistocene Extinction Event - What Caused It? Eos Trans. AGU, Abstract PP41A-03
BECKER (2007): Ice Age Impact. mp3 (4MB). (Interview by the Canadian Broadcast)
FIRESTONE, R.B.; WEST, A.; KENNETT, J.P.; BECKER, L.; BUNCH, T.E. et al. (2007): Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling. Proceedings of the National Academy of Sciences of the United States of America 104(41): 16016-16021
KENNETT, D.J.; KENNETT, J.P.; WEST, A.; WEST, G.J.; BUNCH, T.E. et al . (2009): Shock-synthesized hexagonal diamonds in Younger Dryas boundary sediments. Proceedings of the National Academy of Sciences of the United States of America 106: 12623-12638
KERR, R.A. (2007): Mammoth-Killer Impact Gets Mixed Reception From Earth Scientists. Science 316: 1264-1265
KERR, R.A. (2008): PLANETARY IMPACTS: Did the Mammoth Slayer Leave a Diamond Calling Card? Science Vol.323 : 26
LEVY, S. (2006): Clashing with Titans. BioScience Vol. 56(4) : 292-298
PINTER, N.; SCOTT, A.C.; DAULTON, T.L.; PODOLL, A.; KOEBERL, C.; ANDERSON, R.S.; ISHMAN, S.E. (2011): The Younger Dryas impact hypothesis: A requiem. Earth Science Reviews. Article in Press
UGAN, A. & BYERS, D. (2007): Geographic and temporal trends in proboscidean and human radiocarbon histories during the late Pleistocene. Quaternary Science Reviews.26: 3017-3440

Online Resources:

MORRISON, D. (2010): Did a Cosmic Impact Kill the Mammoths? (Accessed on 23.04.2011)

Blue Marble: 22.000 years of changing earth

"Within a few millennia our ice may be gone, but if we shall have paid a fearful price for its going. Ice at its maximum extent is disastrous, but no ice is worse. The best stage is the halfway one, where we are this blessed moment, but like others it too unstable and will not stay put. We know where we are and which way we are going, but which way we shall be going a little later we do not know."
William Jackson Humphreys (1862-1949), meteorological Physicist.

The project Blue Marble 3000 is a simulation by Adrian Meyer and Karl Rege from the Zurich University of Applied Sciences of the environment changes experienced by earth from the last Ice Age some 21.000 years ago in the past to the Anthropocene some 1.000 years in the future. The simulation is based mostly on freely accessible data of temperature, vegetation, satellite photos and topography:

10.000 to 8.000 years ago the melting ice caps frees huge amounts of water and a dramatic rise of the global sea level follows, in Europe the northern plains of the Mammoth tundra became inundated and the British islands are separated from the European mainland.
6.000 years ago nearly all of the continents of Europe and North America became free of the ice.
By changing atmospheric current patterns more moisture arrives to North Africa, the Sahara is a vast savannah with periodic large lakes until 4.000 years ago, then again a shift in the currents transform this rich environment in one of the largest deserts on earth today.
These environments remains stable for nearly further 4.000 years, then an acceleration of the retreat of the ice caps is visible. The temporal scale changes now from 500 years steps to 50 years steps to emphasize a new epoch - the Anthropocene has begun.

The Iceman story

"I remembered the effect that the view of the tremendous and ever-moving glacier had produced upon my mind when I first saw it. It had then filled me with a sublime ecstasy that gave wings to the soul, and allowed it to soar from the obscure world to light and joy. The sight of the awful and majestic in nature had indeed always the effect of solemnising my mind, and causing me to forget the passing cares of life. I determined to go without a guide, for I was well acquainted with the path, and the presence of another would destroy the solitary grandeur of the scene."

Mary W. Shelley "Frankenstein" (1813)

It was a fast and lonesome death, wounded by an arrow in the back, the man bleed to death within minutes. The body was left on the site of the murder, maybe the aggressors assumed that scavengers and time would erase all of the evidences, but in the cold and dry climate the body begun to desiccate and large scavengers didn't venture in this desolate realm, only some flies were able to deposits their eggs on the body but they weren't able to destroy it.
During the next winter snow accumulated in the gully where the body laid and in the next decades and centuries the snow transformed slowly into ice, protecting and preserving the mortal remains.

Fig.1. The small snowfield on the middle of this photography is covering again the gully in which the body of "Ötzi" was discovered.

Time passed, then in the late summer of 1991 - exact 20 years ago- two German tourists, Helmut and Erika Simon, accidentally discovered the body emerging from the ice, the marked ablation during the summer (helped by sunny weather and the deposition of Saharan dust on the glacier ice, that absorbed much solar radiation) of the small glacier near the Similaun Hut, in the Ötztaler Tyrolean Alps, brought the corpse back to the surface.
The prehistoric mummified corpse - soon known worldwide as "Ötzi" the Iceman - together with its unique set of artefacts, provided a unique opportunity for the research of the cultural development of a bronze-age culture, this corpse is the highest prehistoric find (ca. 3.280m a.s.l.) in the Alps.

But the body and artefacts provided also insights on the glacier dimensions during the little known phases of the warmest parts of the Holocene in Europe. This phase is practically undocumented by glacial sediments, eroded by later glacial advances, and is only recognizable by proxy data like changes in pollen diagrams or dating organic materials, over- or underlying glacial or proglacial deposits.

During the last glacial maximum some 18.000 years ago the entire area was completely ice-covered, only narrow and steep arêtes and horns protruded from the ice. In the area of the Similaun Hut sharp trim lines in a height varying from 3.060m to 3.400m divide the uppermost frost-shattered crests from the lower slopes, smoothed by glacial erosion. The trim line can also recognized locally as marked weathering line that separates different oxidized surfaces (the bed rock consists of Fe-rich gneiss and schist).
A second trim line is marked by an abrupt change in lichen diameter (from 100mm above to 40mm below) and density. The dating by lichenometry attributes this glaciers to the Little Ice Age (LIA, ca. 1.600-1.850), which generally corresponds to the maximum Holocene glacier expansion.
The mummy itself was dated by radiocarbon dating to 4.500+-30 and 4.580+-30 yr B.P., which corresponds to a calibrated age of 5.300-5.050 yr B.P. The relatively sudden burial of the corpse in a more or less permanent snow and ice cover indicates a significant climatic change that induced glacier expansion at the beginning of the Neoglaciation in the second half of the Holocene.
This supposed change of the glaciers was supported also by some soil horizons found in depression between 3.000 and 3.215m a.s.l. and dated to 5.615+-55 yr B.P. (6.450-6.300 cal yr B.P.) and 3.885+-60 yr B.P. (4.416-4.158 cal yr B.P.). Similar recent soils needed at least 5 to 12 centuries for its development, suggesting that the climatic conditions on the site were for a long time relative favourable for biological and chemical activity.

The Iceman and his site so reveal that between 9.000 and 5.000 yr B.P. the mountain glaciers were smaller than in the second half of the Holocene. About 6.400 cal yr B.P. and for several centuries after, an ice-free peripheral belt allowed the accumulation of organic matter and developments of relatively thick soils. Between 5.300 to 5.050 cal yr B.P. ago a rapid climatic change took place, producing a persistent snow cover and the expansion of glaciers, which conserved the body until again the glaciers begun to retreat.
And the recent retreat of the glaciers still continues, in 1970 the glacier that revealed the mummy was part of the much greater Niederjoch Glacier, a composite alpine glacier that descends northward in the Nieder-Valley, but only in the last 5 years the Niederjoch-glacier lost 60-100m length.

Fig.2. The "Similaun" as highest peak (3.597m a.s.l.) with his two main glaciers, the "Similaun" in foreground, and the "Niederjoch" in background. Until ca. 1970 the glaciers flowed together, but the glacier retreat in the last years was notable.

Fig.3. Location (black circle) of the site of the bronze-age mummy in the Ötztaler Alps. Blue areas represents the glacier extends in 2003, the red line the glacier extends during the Little Ice Age (ca. 1600-1850), blue, green and yellow the main glacier-stages during the Pleistocene-Holocene transition.

The environment in which the Iceman lived was characterised by a rich biodiversity, he could use and in fact used an astonishing variety of plants found in his living space.
Both the axe shaft and the long bow were found in the vicinity of the corpse and were made of yew (Taxus baccata), a resistant and elastic wood typ. The quiver for the arrows was made of caprine skin and was stiffened with the elastic wood of the hazel tree (Corylus avellana). The 14 arrows were made of the hard wood of the wayfaring tree (Viburnum lantana). One is repaired, the front end being restored with dogwood (Cornus). The dagger handle is also made by hard wood from a piece of ash (Fraxinus excelsior). Its sheath was knotted from the bark of basswood (Tilia). He carried also two containers made of birch (Betula) bark, in one were found charcoal pieces wrapped in Norway maple (Acer platanoides) leaves.
Several wood species could be identified from the charcoal remains, probably spruce (Picea/Larix-type), pine (Pinus mugo-type), green alder (Alnus viridis), some Pomoideae which were probably Juneberry (cf. Amelanchier ovalis), dwarf willow (Salix reticulata-type) and elm (Ulmus).
A sort of backpack was constructed from a thick branch of hazel (Corylus avellana) bent into a U-shape, together with two coarsely-worked laths of larch (Larix decidua).

The majority of wood species found with the Iceman grow in the montane regions (valley bottoms to 1.800 m), although some subalpine (1.800-2.500 m) and alpine (above 2.500 m) conifer species are also represented. Their ecological requirements point to the transition zone between thermophilic mixed-oak forest communities (Quercetalia pubescenti-petreae) and the montane spruce forest (Piceetum montanum). Norwegian maple (A. platanoides), European yew (T. baccata), ash (Fraxinus sp.), lime (Tilia sp.) and elm (Ulmus sp.) allow to infer a humid habitat with a mineral rich, free-draining soil and a mild winter climate.
All that is similar to the present-day conditions in the woodlands found on the slopes and in gorges in the lower Schnalstal and Vinschgau in South Tyrol, where it is assumed he lived.

So the botanical evidence seems to confirm a climate comparable to modern conditions, and implies a glacial extent similar, if not slightly minor to the present. This has very important influence on the reconstruction of past, and modern climatic and glacial development, and at last the actual discussion about climatic change.

Bibliography:

BARONI, C. & OROMBELLI, G. (1996): Short paper - the alpine "Iceman" and Holocene Climatic Change. Quaternary Research 46: 78-83
MAGNY, M. & HAAS, J.N. (2004): Rapid Communication - A major widespread climatic change around 5300 cal. yr BP at the time of the Alpine Iceman. Journal of Quaternary Science 19(5): 423-430
OEGGL, K. (2009): The significance of the Tyrolean Iceman for the archaeobotany of Central Europe. Veget. Hist. Archaeobot. 18:1-11

AW#31 - Talus Thoughts

Jim Lehane on The Geology P.A.G.E. is asking the question "What geological concept or idea did you hear about that you had no notion of before (and likely surprised you in some way)."

Well I will admit that there is a problem that I come across only in geologically recent times and still puzzles me.

"Beautiful is what we see,
More beautiful is what we understand,
Most beautiful is what we do not comprehend."
Nicolaus Steno, 1673

Can a pile of rubble have e name and be studied? Apparently yes - a Talus (term used in North America, borrowed from the architecture of fortresses)) or Scree (English) can be defined as landform composed of rock debris accumulated by mass-wasting processes - or as pile of rubble. But despite this simple explanation, their humble origin, being often neglected during lectures or considered only disturbing in mapping the bedrock lithology, talus slopes are complex geomorphologic features still holding many secrets (not only to me).
These landforms occur in a wide range of environments, but most predominantly where the climate enforces on steep rock walls or cliffs physical weathering and mass-wasting. If the supplied rubble is enough, the subsequent weathering and removal rate low, a characteristic, thick cone or slope of rock debris can form. Rockfall is one important factor to form a talus; however depending on the catchment are other mass-wasting processes can act on the morphology of the talus, large rock avalanches can occur, debris flows, avalanches and dry grain flows also transport material on the developing slope.
These various processes can alter the form, the composition and the grain size found on the talus - so it is not easy (if possible) to foresee the inner matrix by only observing the surface. In most cases the coarse openwork surface texture is merely a veneer. Talus deposits consist of debris with a wide range of sizes, like a sieve, fine material accumulates in the voids in the deeper parts of the talus. Interestingly for me such a similar phenomenon has been observed also in rock glaciers and landslide deposits - I therefore experienced that is it tricky to map such features as simple aquifers.


Fig.1 and 2. More regular Talus slope / Talus aprons in the upper photo and cataclinal (bedding and slope coincide) slope with various Talus cones and modification by debris flows in the Dolomites.

Fig.3. Example of talus deposits reworked by debris flows (with the typical levees on the sides of the channel) in the Central Alps, area characterized by schists and metasediments. Physical and chemical erosion in such rocks is generally stronger, talus deposits tend therefore to be fine grained and covered by soil and vegetation.
Talus deposits are mainly results of mass-wasting processes, if fluvial ("wet") processes play also or a dominant role the term Talus fans is used.

The overall morphology of a talus slope depends also on the form of the cliffs supplying the debris. Straight plain cliffs will produce a straight sheet talus (Talus slope / Talus aprons), cliffs with channels or gorges will canalize the debris and Talus cones will form. It is mostly that both forms will occur in narrow spatial and temporal succession, a regular cliff will develop channels with ongoing erosion and faults can disrupt the regular conformation of a cliff.
Many talus slope profiles show at least segments with an inclination of 33-35°, a common value for rubble, however considering the entire slope there are significant variations. Mapped talus slopes show that the upper part has an angle of 32-37°, up to 40°, the medial part approaches the value of 33°, the lower part displays low angles and a basal concavity. The segmentation of the profile is in accordance to a change in the facies.
This shape is explained in part by various processes acting along the profile, in the upper part transport and deposition of debris, in the lower part mainly deposition. There is also a change in the grain size caused by "fall sorting": large boulders with their large momentum and energy proceed until the toe of the slope, also the roughness increases downhill, where older large boulders can stop the run of the new arriving boulder. The degree of sorting depends on the slope length, cliff height and the size and shape of dominant particles. This is an important effect of talus slope to be considered when defying a zone of danger or planning mitigation efforts.

Talus slopes in periglacial environments are again peculiar in some characteristics. A snow patch on the base of the slope and subsequent sliding of debris above this surface can produce a distinct ridge, termed protalus rampart or nivation ridge. Covering of snow by such debris is thought to produce an ice-rock mixture that can begin to creep following gravitational pull, a protalus lobe (often unfortunately also referred as protalus rampart), considered by me as one possible variation of rock glaciers.
When the ice melts out, unlike glaciers these lobes can not recede and became fossilised.

Fig.4. Complex talus deposits in the Antersac-Valley, Dolomites. The basal vegetation covered protalus rampart is a relict of a colder climate in a periglacial environment, probably during the aftermath of the last glacial period (18.000-12.000 years ago). Rockfall from the steep cliffs and canalized by a gully provide further debris, forming a talus cone, however the vegetation cover shows that the activity on it today is low. Most recent modifications are erosion of the upper part and secondary mobilization of material by various debris flows.

The coarse debris forming the talus can become preserved, and there is ongoing research to use these deposits to interfere the climate of the past. The presence of a Talus as such is not specific related to climate or environment, however the processes (avalanches, debris flows, grain flows) forming or modifying the Talus are depending on the climate.
Another possibility, despite recognizing the characteristic forms of ice-rock bearing talus slopes, is to try to calculate the accumulation of debris, and so the rate of weathering of the cliff. Assuming that a cold and wet climate increases debris production the ages of talus deposits can provide ages of such climatic phases. In talus slopes composed of carbonate rocks it is also possible to date directly the cement or the matrix formed between large boulders. Measuring the oxygen or carbon isotopes it is possible to recover direct climatic values.


These are only some considerations of many. Talus slopes are wonderful complex landforms, and being common in the region I work, they still continue to fascinate and intrigue me.

Bibliography:

LUCKMAN, B.H. (2006): Talus Slopes. In (ed): ELIAS, SA: Encyclopedia of quaternary science. Elsevier: 2242-2248

Climate research in the geologic past

Fig.1. Global map as published by Lyell in his "Principles of Geology" (8th edition 1850) to illustrate the past climatic changes.

The climate of a region, as experienced by daily observations of a cool morning and hot midday, was for very long time considered simply the result of the height of the sun above the horizon. This idea forced a very simple view of the distribution of climates on Earth, to the poles temperature dropped, to the equator it raised, forming so large parallel climatic belts. Such a static view of the Earth also didn’t need or even allow climate changes in the past or in the future time.
With the establishment of the deep geological time by the first geologists and naturalists it became clear that not only the distribution of sea and land changed over time, but so did climate.

Read on how Lyell explained climate change by shifting "pseudo"-continents over the globe in the post at the American Scientific Guest Blog.

An introduction to Quaternary Entomology

"One may not doubt that somehow, good
Shall come of water and of mud"
"Heaven" by R.C. Brooke (1913)

Beetles are the most diverse group of organisms on earth today. Despite this success they are geologically young, first fossils appear in the Cretaceous and only in the following Cainozoic the group experiences a rapid diversification and radiation. During the last 2 million years of the Quaternary beetles remained relatively stable and didn't experience significant changes or extinction events.
The study of fossil remains of beetles in Quaternary sediments provided both for geology as for biology interesting results.
The fossils provided insights into modern faunas, development as species longevity and population dynamics. In geology beetles are well suited to study the palaeoenvironment of quaternary sediments - their body is highly sclerotized and parts of the exoskeleton can be preserved in organic deposits.

Fig.1. The most sclerotized parts of beetles, like head, thorax and the cover wings (elytra) have the greatest prospect to become preserved in sediments (from BUCKLAND 2000).

Early research on fossil insects of the ice ages was carried out mostly not by professional entomologists, but by geologists, archaeologists or naturalists. This caused a proliferation of new described species with evocative names as Helophorus pleistocenicus (LOMNICKI 1894), Olophrum interglacialie (MJÖBERG 1904) or Lathrobium antiquatum (SCUDDER 1900).
Modern work by entomologists revealed in most cases that the supposedly extinct species are identifiable as modern ones, for example from five Helophorus species described in the early 19th century in the Pleistocene sediments of the Borislav site (Ukraine) as new, today no one remains, and all the specimens were collocated in four extant species.
In 1877 Samuel H. Scudder, entomologist and palaeontologist at the U.S. Geological Survey, published a first paper about fossil insects from the Late Quaternary deposits at Scarborough (Ontario) - he will subsequently dedicate the next 20 years of his life to the research of such remains all over North America.
Scudder following the tradition of the time was a very prolific species seeker, he described more than 1.144 insect species, however already in his lifetime he was criticised for many of these nominations, especially the use of very fragmentary or bad preserved specimen as immortalized in the name he gave to some of them, like Bembidion fragmentum.

Fig.2. Fossil beetles identified by Scudder from the Scarborough Formation, illustrated by Henry Blake in Scudder (1900). (A) Bembidion expletum, (B) Badister antecursor, (C) Pterostichus depletus, (D) Patrobus decessus, (E) Bembidion damnosum, and (F) Patrobus frigidus (from ELIAS 2010).

It was the Swedish entomologist Carl H. Lindroth (1905-1979) who reformed the field of paleoentomology.
By studying taphonomic processes affecting the preservation of insects and by establishing the most useful taxonomic characters, as for example the cuticular microsculpture (microscopic lines and meshes covering the surface of the exoskeleton), he introduced a serious taxonomic comparison between fossil and extant species, clarifying that most beetle species survived unaltered the last 2 million years.

The first work to use insect species to reconstruct a paleoenvironment was carried out by STROBEL & PIGORNI in 1864 on an archaeological site in northern Italy, many other paleontological studies followed in the next decades in Europe.

Fig.3. A tiny fragment of chitin emerging in situ from turf, found in the sediments of a former pond in the central Alps.

In 1955 the English geologist Russell Coope began to study the Upton Warren site near Birmingham (U.K.), searching for fossil mammal bones. The sediments were extraordinary rich of shiny, small fragments of chitin and insect bodies, so Coope tried to delve into this to him completely unknown subject. Patiently he compared the recovered remains with the collection of bugs hosted in the Natural history collections of Birmingham.
Coope was one of the first to compare fossils to recent species, without assuming from the beginning that all Pleistocene insects are extinct species. He published his results of the site of Upton Warren and others in 1959 and 1961.
Today his output counts more than 200 papers, even after retirement he continues his research and his contributions in paleoentomology provided the establishment, diffusion and acceptance of Quaternary entomology in the scientific community and geologists from the 1970 onwards.

Bibliography:

BUCKLAND, P. (2000): An introduction to Palaeoentomology in Archaeology and The BUGS Database Management System. Institutionen för arkeologi och samiska studier, Umea universitet: 62
ELIAS, S.A. (ed.) (2010): Advances in Quaternary Entomology. Developments in Quaternary Science 12: 288
SCUDDER, S.H. (1900): Canadian fossil insects. Geological Survey of Canada, Publication No. 710, Contributions to Canadian Palaeontology 2 (2):67-92
STROBEL, P. & PIGORNI, L. (1864): Le terremare e le palafitte del Parmense, seconda relazione. Atti della Societa italiana di Scienze Naturali, Milano 7: 36-37