Botany for geologists: Lichenometry

Maybe one of the first naturalists to adopt botany on a geological dating problem was the English ambassador in Naples: Lord William Hamilton (1730-1803). Hamilton used the density and kind of vegetation cover to interfere the age of lava flows of Vesuvius.

Today a similar approach is used in lichenometry.
The idea to use the growth of lichens as simply and in field applicable method for relative dating of surfaces was first proposed by the botanist Knut Faegri in the 1930s, and in the 1950s developed further by the Austrian botanist Roland Beschel. During lichenological research on cemeteries he noted that on older gravestones larger lichens can be found. Many of the observed species where also found on rocks exposed by receding glaciers, Beschel realized that lichens could be used to relative date the glacial extensions in the Alps during the Holocene.
Despite the first promising results of lichenometry by botanists and geographers, geologists discovered the use of lichens in alpine or arctic environments only in the decade between 1960 and 1970, since then lichenometry was and is used as a simple field method to date moraines, rockfall deposits, debris flows, denudated rockwalls, escarpments and raised beaches.

Lichens are a symbiotic live community between algae and fungi. The microscopic alga furnishes nutrients for the fungus, the macroscopic visible fungus provide moisture and shelter for the alga. This partnership enables the two partners to colonize habitats, which the single organism couldn't possibly colonize by itself, and in fact as pioneer species lichens colonize an extraordinary variety of habitats and surfaces: Lichens can be found on debris and rock walls to an elevation of 7400m a.s.l., they grow on stems and branches of trees from the tropical to temperate forests, they can be found on rocks in the polar and equatorial deserts, and they colonize the boulders on shores of the sea.

The characteristic growth form or thallus of a lichen species is determinated by the fungus. Lichens growth forms can be divided into three groups based on the shape of the thallus:

- the fruiticose type consists of small tubules and/or branches,

Fig.1. Different Cladonia types.

- the foliose type shows a leaf-like thallus,

Fig.2. Umbilicaria sp.

- and the crustose type develops a flattened thallus overgrowing a surface.

Fig.3. A lichen community on crystalline rock - with a prominent specimen of Rhizocarpon geographicum agg.

This last group comprises the most common members of the lichens, and can be found extensively on almost all hard surfaces, like rocks, tree bark and artificial surfaces from buildings and gravestones. Most species however show a preference for a specific substrate, there are for examples differences in the species richness and assemblage found on carbonate and siliceous rocks.

Considering that lichens like all organisms tend to grow and reproduce it is possible observing lichens to relative date a surface. Given similar rocks and climatic conditions, the larger the lichen colony, or denser or richer the lichen assemblage on the surface, the longer will be the time passed since the growth surface becomes exposed and colonized.
Estimating the absolute age of a material from the lichen growing on its exposed surface first requires the determination of the relationship between observed diameter and age of the individual lichen. After measuring lichens on surfaces of known age, for example by studying surfaces on historic buildings, gravestones or already dated geomorphic features, it is possible to determinate the growth rate and plot a growth curve that relates lichen diameters or surface area to time.
Finally it is possible to compare measurements of lichens on a surface of unknown age with the established grow rate, determinate the age of the thallus and interfering a minimal age for the overgrown surface.

Fig.4. Radially grown specimen of Brodoa intestiniformis.

The colonization and growth of a lichen proceeds in four different phases:

1) Surface got exposed and after a while colonized, this ecesis denominated period is not directly determinable with the lichenometric method, however filed-observations of freshly exposed rocks after glacier retreat shows a lag time of 5 to 100 years, depending on the environmental conditions

2) rapid, logarithmic growth of the thallus

3) the growth rate diminishes, and proceeds in a linear manner

4) When lichens grow old, the growth rate gradually declines until death.

Not all lichen species develop a long-lasting phase with relative constant growth; these species can not be used in lichenometry, also the growth rate depends directly from the studied species and the environmental conditions - the growth is influenced by local, and regional environmental factors, such as temperature, moisture, nutrients, day length and snow cover (the latter factors influencing directly photosynthesis of the algae).
To obtain comparable results in an ongoing study it is necessary to measure thalli of the same lichen species under similar conditions, for example choosing a specific species on similar exposed surfaces of stable boulders.
The photosynthetic productivity in lichens is very low compared to "higher" plants, less than 25% comparing the same photosynthetic active areas between lichens and common plants. This low productivity implies a low growth rate, but also an increased longevity. Some lichen species (like Rhizocarpon geographicum) are estimated to reach (under favourable conditions like in the cold and dry conditions of western Greenland) an age of 5.000 to 9.000 years, the theoretical upper limits of lichenometry. However because lichens colonies eventually grow together, and can no longer be measured individually, lichen as a dating tool are used in a range less than 500 years. Under optimal circumstances lichenometry can provide age accuracy with a margin of error of less than 5 years over the past 200 years.

There are also different approaches, how to measure the single lichens specimens.
One of the simplest and fastest methods is to measure the axis of the five largest individual specimen, more elaborated methods increase the number of measurements or vary the measured parameters, like the diameter of an inscribed circle, the surface area, or the outline length of the lichen. Statistic approaches of the data obtained by these different methods showed that they not influence to much the results; therefore the first mentioned method is one of the most popular and most used.

Lichenometry is considered a useful method applicable in an easy and quick way in the field; however there are limitations and some considerations must be mentioned.
For the fundamental principle of the method, the growth rate of a lichen species, it is necessary to find appropriate lichen colonized surfaces of known age. The surface and the single specimens that will be measured and dated must also fullfil some requirements. Not all surfaces are equal, snow cover, sunshine exposure can vary, selected boulders can be instable and their changes of position can influence the growth of lichens.
The large scale climatic factors must be considered during the selection of survey sites, different climatic conditions can it make impossible to use the same growth rate for different valleys, even if geographically they are adjacent.
Despite the restricted numbers of species used in lichenometry, the method at least implies a basic knowledge of the lichen species and their classification. Some lichen species are very similar on a macroscopic scale and differ only slightly in colour or general growth pattern, also the colour of some species tends to change with age.
Despite the omnipresence of lichens, they are often neglected by non-botanists (and even botanists), good books on the matter for non specialists are rare, and important information's are often not divulged. For example one of the most used and well known lichen species by earth scientists, R. geographicum, according to botanist in fact is not a species, but an aggregate of different groups, with slightly different properties, resulting in possible implications on lichenometry not yet fully considered.

Despite these last considerations, lichenometry has proven to be an inexpensive, widely adaptable, and invaluable tool for use in estimating surface ages in lichen-dominated landscapes also for the geologist.

References:

McCARTHY, D.P. (2006): Lichenometry. 1399 - 1404 In (ed): ELIAS, S.A. (2006): Encyclopedia of quaternary science. Elsevier.
WALKER, M. (2005): Quaternary dating methods. Wiley Press: 304

August 21, 1986: The Lake Nyos catastrophe

The 21. August 1986 was market day in the village of Lower Nyos (Cameroon), from the surrounding mountains many herdsmen brought their livestock to do business with the local farmers. In the evening, at 21.30 p.m. most of the peasants and their guests were sleeping and didn’t notice the sound of an explosion coming from Lake Nyos, two kilometres distant to the village.

The few survivors report that their family members were eating, in the very next moment suddenly tumbled on the floor, death. A woman awaking the next morning found their five children dead in their hut. In Nyos that evening 1.700 people died. Rescue troops that arrived in the valley some days later reported of a sinisterly scene, villages with huts and gardens untouched, but everywhere bodies of humans and animals, there weren’t even insects on the corpses.The unseen killer was a 50m high cloud composed of 1,6 million tons of carbon dioxide, erupted from Lake Nyos and denser then the surrounding air following the valley for 27 kilometres, killing more then 1.700 people and 3.000 animals.

Fig.1. Lake Nyos as seen some days after the catastrophic release of carbon dioxide. It is thought that the violent degassing mobilized the lake sediments from the bottom and huge waves eroded part of the steep shores, bringing sediments in suspension and colouring the lake brown. On the border are various landslide scarps visible, it is possible that a landslide triggered the degassing of the lake (photo credit LOCKWOOD 1986).

Fig.2. Carcasses of animals as found some days later after the catastrophe, the bodies showed no injuries, the animals were asphyxiated by the carbon dioxide erupted from the lake (photo credit LOCKWOOD 1986).

This deadly phenomenon is explained by the geological position of Lake Nyos, situated in a volcanic caldera.
Calderas possess steep walls and cliffs delimiting it, so that if the Caldera becomes filled with water, the resulting lake is relatively deep. Because of their depth, these lakes show a strong temperature gradient between superficial and bottom water layers, resulting in different water densities. In temperate zones during summer the warmer and lighter water remains at the surface, preventing deep reaching currents and a mixing of the different layers. During spring and autumn the surface water cools, and sinks to the bottom. However in the tropics the constant warm climate during the entire year prevents this cooling, so that the bottom water becomes impoverished in oxygen and enriched in gasses emanating from the volcanic ground, mainly carbon dioxide, or created from the decomposition of organic material, mainly methane, for many years. This poisoned zone is called Monimolimnion. In a depth of 200m the water can so accumulate ten times more carbon dioxide then on the surface.

It’s not definitively known what finally triggered the lethal eruption of Nyos, it was speculated that an earthquake or submerged volcanic eruption disturbed the water stratification in the lake, enabling the accumulated carbon dioxide to escape its wet prison.
The days before August 21 were rainy; it is also possible that the rainfall cooled the superficial water layers so much, that an intermixing with the denser and poisonous water occurred.
A fourth possibility, supported by the observations of various landslide scarps on the shores of the lakes, is that a landslide triggered by the rainfall felt in the lake, disrupting the layering of the water column, and so eliminating the “cap” that prevented the carbon dioxide bubbling out from the gas rich bottom water.

The particular settings necessary for poisonous lakes, resulting from their geographic, climatic and geological circumstances, is known for only three lakes. Lake Nyos and Lake Manoun located in Cameroon, and Lake Kivu located at the border of Ruanda and Congo.
On August 15 1984 an explosion, probably caused by the release of gases, at Lake Manoun killed 37 people.

At Kivu, with his densely populated shores, the concentration of lethal gases, in part of volcanic, in part of bacterial origin, in a depth of 500m is extraordinarily. If an event like at Nyos happened, the live of hundred of thousands of people would be threatened. To prevent a natural and presumably catastrophic degassing of the lakes, in the last years the lakes are intensively monitored and the bottom water is brought to the surface under controlled conditions by tubes, where it can degas.

References:

DECKER, R. & DECKER, B. (1991): Mountains of Fire: The Nature of Volcanoes. Cambridge University Press. Cambridge: 243

Online Ressources:

LOCKWOOD, J. (1986): Oku Volcanic Field (Accessed 19.08.2010)

August 20, 1890: 120 years Lovecraftian Geology

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

The short extract is the introduction of "At the Mountains of Madness", a horror story by the American writer H. P. Lovecraft (born on 20. August 1890 in Providence) written in February/March 1931 and originally serialized in the February, March and April 1936 issues of Astounding Stories (one of the first pulp- and horror fiction magazines).

The story follows the tradition of the Cthulu-mythos - anyways presenting a more science (-fiction) approach to explain the rise and fall of the ancient god, and especially the elder ones. The story is written in first-person perspective by the geologist William Dyer, a professor from Miskatonic University (one of the institutions that possess a copy of the forbidden Necronomicon).

A geological Antarctica-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 the Himalaya in the remotest corner of this frozen world. But after a carefully investigation at the borders of the mountain range of more strange fossils, contact get lost with the team, and the narrator makes his way to discover what happened at the Mountains of Madness.

Lovecraft had a lifelong interest in the exploration of the Antarctic continent. The biographer S. T. Joshi notes, that "Lovecraft had been fascinated with the Antarctic continent since he was at least 12 years old, when he had written several small treatises on early Antarctic explorers.”

By the 1920s Antarctica was one of the last unexplored regions of the earth, where large stretches of territory had never seen the tread of human feet. Contemporary maps of the continent show a number of provocative blanks, and Lovecraft – as a writer- could exercise his imagination in filling them in. In fact the first expedition of Richard Evelyn Byrd took place in 1928-1930, the period just before the novella was written, and Lovecraft mentioned the explorer repeatedly in his letters, remarking at one point on "geologists of the Byrd expedition having found many fossils indicating a tropical past".

Lovecraft's was not only a passionate autodidact in geology, but also in American classic literature. Most obvious literary source for At the Mountains of Madness is Edgar Allan Poe's lone novel, The Narrative of Arthur Gordon Pym of Nantucket, whose concluding section is set in Antarctica. Lovecraft twice cites Poe's "disturbing and enigmatic" story in his text, and explicitly borrows the mysterious phrase "Tekeli-li" from Poe's work. Also, a graduate student, seeing at the arrival of the expedition on the McMurdo-Sund the active volcano Mt. Erebus, cites poetry by E.A. Poe to describe the scenery.

Many of the first Lovecraft's stories involve features that appear to be supernatural, such as monsters, demons and the occult, without clear explanation from where they come, or what they are. However, Mountains appears to explain the origins of such elements like the occult symbols or to "gods" such as Cthulhu in rational terms, by terrifying scientific facts - like the fossils, or inscriptions found on cyclopic walls of a sunken city. Mountains explains many elements of the "Cthulhu Mythos" and the origin of the crinoid-like very, very old elder ones .

Lovecraft with this story not only presents a weird tale, but also insights of the geological conceptions nearby 120 years ago - worth to be known by ever geologist to dare to approach the outer limits of geomadness.

Indonesia's Last Glacier

One of the strangest regions with glaciers can be found on the equatorial island of Indonesia, here on the mountain range of Pegunungan Maoke, emerging from the tropical jungle and with peaks reaching heights of 4.884m (Carstensz-Peak, conquered only in 1962 in the Puncak Jaya massif) still ice fields persists, but they are continuous shrinking.

Fig.1. Index map of Irian Jaya showing the location of the highest mountains, figure from ALLISON & PETERSON 2000.

A research team under the auspice of Dr. Lonnie Thompson, specialized on glaciers of the equatorial region, is actually trying to take as much ice cores as possible from the last persisting ice fields of the Carstensz-Peak.
All the “glaciers”, a terminus to be adopted only if the ice shows an active movement, otherwise the correct term is “ice fields”, have experienced a pronounced retreat in the last century, and the predominant rainy weather of the last years on the mountains is melting rapidly the remaining ice and warming the bedrock. So in 2003 the ice field of the 4.760m high Puncak-Mandala and the ice field of Puncak Trikora (4.730m) disappeared, and the last remaining glaciers of the oceanic realm, the North Wall Firn, the Meren Glacier, and Carstensz Glacier surrounding the Carstensz-Peak, experienced massive volume and surface loss (less then one square kilometre persists) and got fragmented in various inactive parts.

Fig.2. Oblique aerial photograph looking east at several of the glaciers on Puncak Jaya in 1936. Left to right: Northwall Firn, Meren Glacier, and Carstensz Glacier. Photograph from ALLISON & PETERSON 2000.

Fig.3. Oblique aerial photograph looking east at the glaciers in 1972. Photograph acquired during the Carstensz Glaciers Expeditions (CGE). Compare with figure 2. Photograph from ALLISON & PETERSON 2000.

The researchers were able to recuperate two 30m long ice cores which show an annual layering and will be studied to determinate the climatic variability of the region.

The ice-archive on the mountains of Indonesia's Papua Province are an important stratigraphic record for the climate at the border of the Pacific Ocean, one of the largest basins were thermic energy is stored in the sea or released to the atmosphere, influencing the climate on the whole planet.

Online Resources:

ALLISON, I & PETERSON, J.A. (28.04.2000): Satellite Image Atlas of glaciers of the World - GLACIERS OF IRIAN JAYA, INDONESIA. (Accessed 19.08.2010)
Ice Core Paleoclimatology Research Group (Accessed 19.08.2010)

Geology history in caricatures: A Coprolitic Vision

Approach, approach, ingenuous youth,

And learn this fundamental truth:
The noble science of Geology
is founded firmly in Coprology
P.B. Dunacn quoted in BUCKLAND, F. 1883

Cartoon drawn and published in the EARTH magazine by Callan Bentley, used here with kindly permission (thanks)

This post is a tentative submission to "The Carnal Carnival!"

Coprolites, from the Greek "kopros" and "litos", roughly translated into dung stone, can be regarded as a variety of ichnofossils (trace fossils), defined more precisely as fossilized, large biodepositional structures, documenting the presence, behaviour and physiology of an animal (PEMBERTON& FREY 1991).

The scientific term was introduced by the notorious eccentric, but also ingenious British Reverend William Buckland (1784-1856).
Buckland's interest in animal faeces arose from his studies on cave deposits and intermixed organic remains. In various caves that he visited, he noted scattered bones and white deposits, which he interpreted to be hyenas’ droppings preserved on the cave floor. To verify this hypothesis, he actually fed a spotted hyena from a travelling menagerie with ox bones, and on the next day compared the gnawed bones and the new available droppings with the old coprolites, concluding that there was "no difference between them, except in point of age" (BUCKLAND 1823).

Despite the modern approach and the astounding result - Buckland could demonstrate that the bone accumulations of caves where not caused by a biblical flood, the still proposed explanation of the time - his friend the chemist William Wollaston, who accepted to analyse the droppings (resulting of phosphatic composition, similar to the fossil ones) confessed to Buckland:

"though such matters may be instructive and therefore to a certain degree interesting, it may as well for you and me not to have the reputation of too frequently and to minutely examining faecal products."

In May 1829 Buckland began to write down the research on coprolites in some preliminary papers, in his final draft of the work published in 1835 he included his cave experiences and the research on the fossil faeces of Ichthyosaurus from the Lyme Regis area in Dorset, region he visited guided by the famous amateur fossil collector Mary Anning. Curious to note that until the study of Buckland the faeces fossils found at Lyme Regis were regarded as fossil fir cones.

“It has long been known to the collectors of fossils at Lyme Regis, that among the many curious remains in the lias of that shore, there are numerous bodies which have been called Bezoar stones, from their external resemblance to the concretions in the gall-bladder of the Bezoar goat, once so celebrated in medicine: I used to imagine them to be recent concretions of clay, such as are continually formed by the waves from clay on the present beach; but I have now before me sufficient evidence to show that they are coeval with the lias, and afford another example of the same curious and unexpected class of fossils with the album graecum which I first discovered in 1822 in the cave of Kirkdale, being the petrified faeces of Saurian animals, whose bones are so numerous in the same strata with themselves.” (BUCKLAND 1835)

Buckland, observing the narrow spatial context between the bones of the Ichthyosaurs, hyenas and the excrements coins even one of the first Ichnogenera, letting no doubt what he is referring at:

“I propose to assign the name Ichthyosauro-coprus to the fossil faeces which are thus evidently derived from ichthyosauri.” (BUCKLAND 1835)

“I need only refer to the account given in my Reliquiae Diluvianae, of the faeces of hyaenas in the Cave of Kirkdale, and to the large quantities of the same substance that have subsequently been discovered at Torquay and Maidstone, an din the Cave of Lunel, to show how frequent is the occurrence of Hyaeno-coprus in diluvial mud and gravel.” (BUCKLAND 1835)

Buckland adopted also in the liassic case his actualistic - comparative method to infer a possible behaviour of the extinct animals:

"Dispersed irregularly and abundantly throughout these petrified faeces are the scales, and occasionally the teeth and bones, of fishes, that seem to have passed undigested trough the bodies of the Saurians, just as the enamel of teeth and sometimes fragments of bone are found undigested both in recent and fossil album graecum of hyenas..[]..The bones are chiefly vertebrae of fishes and of small Ichthyosauri;...[]..still are sufficiently numerous to show that these monsters of the ancient deep, like many of their successors in our modern oceans, may have devoured the small and weaker individuals of their own species." (BUCKLAND 1835).

"The author concludes that he has established generally the curious fact, that, in formations of all ages, from the carboniferous limestone to the diluvium, the faeces of terrestrial and aquatic carnivorous animals have been preserved; and proposes to include them all under the generic name of Coprolite." (BUCKLAND 1835).

Fig.1. Copy of the plate illustrating coprolites of Tertiary Strata, from BUCKLAND 1835. Buckland fashioned a large collection of coprolites from the Lias of Lyme Regis, but also from Carboniferous and Tertiary strata. Some examples in this plate however are artificial ones, fabricated by Buckland to prove his argument. The ingenious Buckland filled the intestine of sharks and dog-fishes with cement, and later sectioned the animals to recover the resulting cast and compare them to the fossil ones.

Despite his scientific approach to the matter, Buckland (like in many other subjects) never take it and his research to serious. His Son, Frank Buckland, remembers:

"Some of these coprolites have been turned to purpose of art, under the name of "Beetle-stones". Dr. Buckland had a table in his drawing-room that was made entirely with these coprolites; . . and which was often much admired by persons who had not the least idea of what they were looking at." (BUCKLAND, F.T. 1883)

It’s seems obvious that contemporaries would make fun of this dedication to the art of coprology - and one of the most fitting cartoons regarding Bucklands’ passion comes from the geologist, and good friend of Buckland, Henry De la Beche.

Fig.2. De la Beche caricature "A Coprolitic Vision", lithograph print ca. 1829, image from here.

"Although he appreciated the value of his friend's scientific insights, De la Beche could not resist the temptation to caricature this "Coprolitic Vision". he produced a lithograph (ca. 1829) showing the "Reverend Professor of Mineralogy and the Geology in the University of Oxford", dressed in gown and mortar-board, and standing on a flat rock at the opening of a long cavern shaped like the nave of a cathedral. The columns supporting the roof where bloated spiral-shaped bezoars, and Buckland, with a geological hammer in his right hand, as it were conducts a service attended by animals - a deer, a bear, hyenas, a leopard, crocodiles, ichthyosaurs and pterodactyls. Every member of the choir and congregation are shown in the act of defecating. There are even large cylindrical shapes on the rock in the foreground, and one beneath Buckland's own legs." (McCartney 1977)

References:

BUCKLAND, F.T. (1883): Curiosities of Natural history. Second Series. Richard Bentley and Sons. London: 360
BUCKLAND, W. (1823): Reliquiae Diluvianae; or Observations on the Organic Remains Contained in caves, Fissures, and Diluvial Gravel, and on Other geological Phenomena, Attesting the Action of an Universal Deluge. John Murray. London: 303
BUCKLAND, W. (1829): Additional remarks on coprolites and fossil sepia. Proceedings of the Geological Society of London 11: 142-143
BUCKLAND, W. (1835): On the discovery of coprolites, or fossil faeces, in the Lias at Lyme Regis, and in other formations. Transactions of the Geological Society of London, second series 3: 223-236
McCARTNEY, P.J. (1977): Henry De la Beche: Observations on an Observer. Friends of the National Museum of Wales. Cardiff: 77
PEMBERTON, S.G. & FREY, R.W. (1991): History of Ichnology: William Buckland and his "Coprolitic Vision". Ichnos 1: 317-325

Earthquake reported on the Aeolian Islands

This afternoon at 14.54 MET the Italian Aeolian Islands were shacked by an earthquake of an estimated 4.5 magnitude after Richter. According to preliminary press releases of the Italian Institute for Geophysics and Volcanology the hypocenter of the earthquakes is situated 6 kilometres east of the island of Lipari, in a depth of 19,1 kilometres. The trembles were averted on the islands of Vulcano, Lipari, Salina and on the coast of Sicily in the cities of Palermo, Catania and of Messina.

Fig.1. Map of the Aeolian Islands (after Wikipedia).

The earthquake triggered some landslides at Lipari, rock fall on the flanks of the mountain of Vulcano and on Salina. In the village of Lipari minor damages are reported and parts of the beach of the island were closed for reasons of safety. Minor rock falls occured on Lipari also two days later (17.08.2010).

The actual information's releases are contradictory. In a first communication 7-4 injured persons on Lipari, resulting from accidents by rock falls- and landslides, were reported, this information was later withdrawn, only one emergency call and damages on buildings and roads are confirmed, there are no casualties (16.08.2010).
This seismic event is not unusual for the area, in fact the region is characterized by frequent, but deep located earthquakes with a small magnitude (ca. 2-3) produced by the subduction of the Ionian plate under the Tyrrhenian plate.

Fig.2. Simplified sketch of the tectonic setting (red lines) of Southern Italy, the Tyrrhenian Sea is moving south, pulled by the receding subduction zone south of the Ionian Sea. Meanwhile Sicily is pushed relative to the Tyrrhenian Sea to the north, in the junction zones eartquakes can generate and volcanism develop.

Stronger earthquakes are much more rare, seismic events with a magnitude of 4 are documented 3 times in the last 4 years (27.02.2006 / 18.08.2007 / 27.10.2008), the strongest earthquake recorded on the Aeolian island occurred on April 15, 1978 with a magnitude of 6.1, the epicentre was located some 30 kilometres more to the south compared to the actual one.

The actual earthquake caused more scare then damage; it was sensed so distinct because of the minor depth of the hypocenter compared to the usual events in the region. Monitoring is still ongoing, and there is the possibility of minor aftershocks in the next days (a minor shake of 2.3 occured Monday evening 16.08.2010).

Online Resources:

Istituto Nazionale di geofisica e Vulcanologia (accessed 16.08.2010)
Video (in Italian) about the seismicity in Italy between 20.07-03.08 (accessed 16.08.2010)

Creationism debate in the year 3001

Prof. Hubert J. Farnsworth defends evolution in the 31th century against creationism claims of the 20th century, and after realising there are still gaps before Darwinius masillae he decides to go find himself the missing missing-link.



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