The discovery of the periglacial realm

The term periglacial was introduced by the Polish geologist Walery von Lozinsk in 1910 and 1911 to describe the particular mechanical weathering he had observed in sandstones of the Gorgany Range in the southern Carpathian Mountains - today the reactions of the permafrost to changing temperatures is one of the major fields of research. Read more about the periglacial realm on the American Scientific Blog.

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.

Glacier outburst floods threat

Glaciers can influence societies in their catchment area in different ways, they act as a water storage for dry summers, but glaciers can also trigger geological catastrophes and endanger people.

Glacier outburst floods (GOF) refer to the rapid and sudden discharge of water from within a glacier or from an ice-dammed lake, within minutes to hours a flood wave occurs possibly damaging infrastructures and killing people kilometres away from the glacier which initiated the disaster. In the Alps and North America most outburst floods occur in summertime when during melt-season large quantities of water can accumulate inside the glacier or as ice-dammed lake.

In the Andes and the Himalaya also a second type of floods is common, outbursts from moraine-dammed lakes, referred as glacial lake outburst flood (GLOF).
The area between the moraine and the retreating glacier can be filled with the melt-water, and as the glacier continues to shrink the lake continues to grow. Various processes can lead to the failure of a moraine dam, waves and currents of the lake can erode the dam, ice contained in the dam can melt, the detritus forming the dam can settle with time and so lowering the effective height of the dam.

Fig.1. Laguna Paron (4.140m a.s.l. Cordillera Blanca - Peru, foto from Wikipedia) in 2009, a lake dammed by the debris-mantled glacier Hatunraju with a capacity of 75 million cubic metres before the lake level was lowered by 20 meters artificially by tunnelling through bedrock on the left of the moraine dam. The lake is surrounded by moraines 250m high. It is unknown how stable the moraine of Hatunraju is, if this dam fails a flood of around 50 million cubic metres could sweep downstream and severely damage the town of Caraz, 16 kilometres away.
The worst glacial lake outburst in historic time was caused by the failure of such a moraine-dam in Peru. December 3. 1941 the town of Huaraz was partially destroyed by a flood that killed 60.000 people.

Floods resulting from moraine-dam failure have been increasing in frequency in the Himalaya over the past 70 years or so, although in terms of loss of life they have been by accident much less disastrous then in the Andes.
One of the best-documented outburst floods in Nepal took place on 4. August 1985 when the terminus of the Langmoche Glacier in the Khumbu Himal collapsed into Dig Tsho glacial lake (Video), creating a displacement wave hat overtopped the moraine dam and triggered its collapse. Estimated 10 million cubic metres of water were released - the wave destroyed a power plant and five people were killed and eroded and destabilized the valley floor for 90 kilometres downstream.

This case triggered major research projects of potential dangerous glaciers and glacial lakes, until 2004 more then 20 potentially dangerous lakes in Nepal and 24 in Bhutan were identified, one of the most impressive and dangerous case was lake Tsho Rolpa (4.450m a.s.l.), fed by the Trakarding Glacier. By 2002 the lake was 3,5 kilometres long, 0,5 kilometres width and 135m deep, with an estimated volume of 110 million cubic metres. The moraine damming the lake up was 150m high, with a core of decaying ice.
Emergency measures were initiated with the installation of an early-warning system to detect downstream travelling a flood-wave and later by the construction of an artificial spillway, lowering the lake by 4 metres.
However these are considered only temporary solutions, as a lowering of the lake level by at lest 15 to 20 metres is necessary to prevent spillover or failure of the dam crest, a costly procedure in this region.

This last case shows also the financial problems facing poor countries, often disaster prevention or mitigation are limited by the available resources, and considering the continuing glacier retreat expected in the next decades the increase of problematic lakes (both in number and volume) will by of major concern in the future.

Fig.2. The glacierized Himalayan border region of Bhutan (bottom) and Tibet (top) seen in a satellite image. From the crest of the mountain range clean glaciers flow northwards onto the Tibetan Plateau, while debris-mantled glaciers flow south into densely forested valleys.
At bottom right are a series of moraine-dammed lakes and incipient lakes, formed by the rapid coalescence of supraglacial ponds. The large lake at the very right is lake Luggye Tsho. A breach of the dam in 1994 led to severe flooding and loss of life up to 200 kilometres downstream. (ASTER-image by NASA, 08 June 2006).

Bibliography:

HAMBREY, M. & ALEAN, J.(2004): Glaciers. 2nd ed. Cambridge University Press: 377
HORSTMANN, B. (2004): Glacial Lake Outburst Floods in Nepal and Switzerland. New Threats Due to Climatic Change. Germanwatch - Bundesministerium für wirtschaftliche Zusammenarbeit und Entwicklung.
KALTENBORN, B. P., NELLEMANN, C., VISTNESS, I. I. (Eds) (2010): High mountain glaciers and climate change - Challenges to human livelihoods and adaptation. United Nations Environment Programme, GRID-Arendal.

Modeling Glacier Change 2000-2100

According to a simulation by researchers of the University of Alaska (RADIC, V. & HOCK, R.) and based on various scenarios of precipitation change and a temperature increase, with a mean value of ca. 2°C, as predicted by most climate models, until the year 2100 the 120.000 glaciers located (mainly) in middle latitudes will experience a massive loss of 21% of the actual ice volume.

Observing the reactions of more than 300 glaciers to the climatic change in the period of 1963 to 2004 the models were extrapolated to simulate a significant increase in temperature and slight increase in precipitation and the effects of these variables on the mass balance of the glaciers.
The projections show in the 19 chosen glacierized regions different glacier retreat values, depending from factors like elevation, surface properties and effective temperature rise in the region.
According to the proposed scenarios, mountain ranges in temperate climatic zones will experience the most massive volume change, in the European Alps glacier will loss up to 75% of the actual ice volume, similar values to the New Zealand Alps with 72% and the Caucasus.
In contrast mountain ranges with a high average altitude, like in Asia or the Andes, will experience much lower loss percentages, with an average value of 20%.

I discussed a previous research dealing with possible effects of such glacier retreat on human society in this post.

Fig.1. Regional twenty-first-century glacier volume change expressed in per cent from initial volume in year 2000, the results are presented for 19 regions based on temperature and precipitation projections from the ten applied climatic models, after RADIC & HOCK 2011.

Fig.2. Example of glacier retreat in the Alps in the past 100 years: The Waxegg-glacier in the Zillertaler Alps at the border between Austria and Italy ca. 1900-1903 and 2006. Historic image from ROTHPLETZ, A. & PLATZ, E. (1903): Alpine Majestäten und ihre Gefolge - Die Gebirgswelt der Erde in Bildern, 268 Ansichten aus der Gebirgswelt.
For the history of glacier monitor projects see this post.

Bibliography:

RADIC, V. & HOCK, R. (2011): Regionally differentiated contribution of mountain glaciers and ice caps to future sea-level rise. Nature Geoscience doi:10.1038/ngeo1052

Cool Science at Scientific American

Since antiquity snow-covered peaks have been ignored, avoided or even feared by men - up here apparently there was nothing to be gained.
But in search of adventure and knowledge during the 19th century mountains and glaciers became more and more visited by mountaineers, naturalists and even queens - and today the science of glaciers demonstrate urgently how the climate and our interference is changing the world.

Thanks to Bora Zivkovic and the editors of Scientific American I was allowed to present A Short History of Glacier Science at the journal´s Guest Blog.

Fig.1. Queen Margherita of Italy (second from left) and company climbing the Monte Rosa (4.420m) in the Italian-Swiss Alps in the year 1893. The Queen was determined to inaugurate in person a weather station on the summit on the mountain (from BAILEY 1983).

Bibliography:

BAILEY, R.H. (1983): Glacier. Time-Life Books, Amsterdam: 176

The discovery of the ruins of ice

"It has already been said, that no small part of the present work refers to the nature and phenomena of glaciers. It may be well, therefore, before proceeding to details, to explain a little the state of our present knowledge respecting these great ice-masses, which are objects of a kind to interest even those who know them only from description, whilst those who have actually witnessed their wonderfully striking and grand characteristics can hardly need an inducement to enter into some inquiry respecting their nature and origin."

James, D. Forbes (1900): "Travels Trough the Alps." [page 17]

Fig.1. C. Wolf and M. Descourtis "La Grosse Pierre Sur Le Glacier de Vorderaar Canton de Berne Province d'Oberhasli", Amsterdam 1785.

Today worldwide glaciers were studied and monitored as climate proxies, and the recent measurements show that almost all of them are retreating fast. The story about glaciers, their influence on the landscape and their possible use to reconstruct and monitor climate is an intriguing one, with many triumphs, setbacks and changes of mind.

For centuries, if not even millennia, the high altitude belt of mountain ranges were a region visited and travelled by man, however also haunted and forbidding places. The glaciers, masses of ice enclosing peaks and extending their tongues into valleys, were considered the residence of mountain spirits, then during the medieval times the prison of damned souls (the Italian poet Dante Alighieri 1265-1321 imagined the centre of hell as a frozen wasteland) and the playground of demons, who from time to time send avalanches and debris flows into the valley.
Despite these myths there was some early insights of what glaciers actually really are made, the Greek historian and geographer Strabo (63 - 23) describes a voyages trough the Alps during the reign of Augustus and mentions

"…there is no protection against the large quantities of snow falling, and that form the most superficial layers of a glacier…[]. It's a common knowledge that a glacier is composed by many different layers lying horizontally, as the snow when falling and accumulating becomes hard and crystallises...[]."

However the knowledge got lost, and was only rediscovered during the Renaissance. Leonardo da Vinci´s (1452-1519) is considered one of the greatest Renaissance-geniuses, he studied anatomy, biology and geology, however regarding the glaciers of the Alps his ideas were somehow confused, the thought glaciers were formed by not melted hail accumulating through the summer. But soon the study of nature experiences an incredible raise, and glaciers find place in various descriptions of travelling scholars.

Between 1538 and 1548 glaciers were labelled (even if not depicted) with the term "Gletscher" on topographic maps of Switzerland. In his account on the Swiss land the Theologian Josias Simler in 1574 describes the Rhone-glacier.
The first historic depiction of a glacier is considered the watercolour-paint of the Vernagtferner in the Ötztaler Alps from 1601. The Vernagtferner was a glacier that repeatedly dammed up the Rofen-lake (named after the Rofen-valley), which outbursts caused heavy damage and loss of property, particularly in the years 1600, 1678, 1680, 1773, 1845, 1847 and 1848.
In 1642 the Swiss editor Matthaeus Merian the Older in his "Topographie Helvetiae, Rhaetiae et Valesiae" published various copper engravings of glaciers, and in 1706 Johann Heinrich Hottinger is interested to explain the motion of "the mountains of ice" in his "Descriptio Montium Glacialium Helveticorum."
Johann Jakob Scheuchzer, visiting in the year 1705 the Rhône Glacier, published his observations of the "true nature of the springs of the river Rhône" in the opus "Itinera per Helvetiae alpinas regiones facta annis 1702-1711", and confirms the idea that glaciers are formed by the accumulation of snow and they move and flow.

Fig.2. The description of the Rhone glacier according to Scheuchzer´s "Itinera per Helvetiae alpinas regiones facta annis 1702-1711", the engraving shows the "false springs at the mountain Furca" (M, N, O - left and right of the picture) and the "true springs" (J, K, L) coming from the snout of the "great glacier" (A-F), surrounded by the "small glacier" (G, H).

The increasing interest to study glaciers in the Alps is also encouraged by enthusiastic travel reports; in his "Voyage pittoresque aux glaciers" the A.C. Bordier of 1773 describes the Bosson glacier as a "huge marble ruins of a devastated city".
The naturalist Horace Benedict de Saussure (1740-1799) is fascinated by the mountains of his homeland, he climbed mountains around Geneva since 1758, and after 1760 he travelled more than 14 times trough the Alps (considering the possibilities in this time an extraordinary achievement). Between 1767 to 1779 the first volume of his "Voyages dans les Alpes" is published, were he reassumes his observations and theories about the visited glaciers, he recognized moraines and large boulders as the debris accumulated by the glacier tongue and proposes to map them to interfere the former extent of glaciers. Despite this exact statement, de Saussure failed to connect large boulders found in the foreland of the mountains to the glaciers of the Alps. He assumed that these rocks were transported on their recent locations by an immense flood. That seemed to explain why most of the boulders found scattered around the plains of Germany came in first place from the regions of Scandinavia, where the same lithology where found in the crystalline continental basement, like Precambrian metamorphic rocks and paleozoic sediments. The theory worked lesser to explain the foreland Alpine rocks - to transport boulders from the Alps the flood at least had to reach 1000 of meters.
The idea of a flood as the explanation for "glacial" deposits became largely accepted, it seemed to fit the description of the biblical flood; even Lyell and Darwin assumed that huge erratic boulders were transported by swimming ice drafts on top of a flood wave.
That glaciers could propagate far out of their valleys was however not an unusual idea for local inhabitants, who observed and experienced the growth and recess of glaciers. In academic circle this approach was a little more difficult.
A contest thought to demonstrate the former extension of Swiss glaciers initiated by the Swiss pastor Jakob Samuel Wyttenbach in 1781 (maybe inspired be the advance of the Alpine glacier in 1770) didn't arise any interest.

"Could it be proven to ourselves on the available documentation that both by the progress of our ice mountains as by our misbehaviour once for pasture most suitable land is currently covered by ice…[]"

There were only careful speculations considering a former expansion of glacier: the geologists James Hutton (1726-1797) and his friend John Playfair (1748-1819) speculated about glaciations of the northern hemisphere. In 1826 a publication by the Danish mineralogist and mountain climber Jens Esmark (1763-1839) was translated into English, in this paper Jesmark discussed the possibilities that glaciers where much greater in the past then today. J.D. Forbes and Robert Jameson (who were the geology professors of Charles Darwin at Edinburgh University, Darwin in his autobiography of 1876 remembers "The sole effect they produced on me was the determination never as long as I lived to read a book on Geology or in any way to study the science.") discussed glacial theories during their lectures. And even Buckland, who still in 1831 argued "northern region of the earth seems to have undergone successive changes from heat to cold", in 1837 was converted to Lyell's uniformatism and considered that sudden changes, like an ice age and glacier expansion, simply don't happen in geology.

In 1815 Jean Pierre Perraudin, a chamois hunter in the Val de Bagnes, told to the engineer Ignatz Venetz his theory that the glaciers once covered the entire valley, and Venetz mapped features that made him even recognize that once the entire Swiss was covered by ice. Vernetz´s lecture on the assembly of the Swiss association for natural history in 1829 found little interest, only Jean de Charpentier, director of the salt mine in the city of Bex (Western Swiss), who 14 years earlier had meet and discussed with Perraudin, this time accepted and got interested in this theory.
He begun a detailed mapping project, and in 1834 Charpentier presented again before the Swiss association the results of his investigations, but the flood theory had still much supporter. One of the critics in the public was a former student of Charpentier, named Jean Louis Rodolphe Agassiz, respected palaeontologist by the establishment. Charpentier invited Agassiz to visit the city of Bex and surrounding mountains, and to observe glaciers.
In the following year (1837) Agassiz held an enthusiastic lecture about glaciers, ice ages and ice shields, and in 1840 published a detailed study of modern glaciers, their deposits and their spurs in his "Etudes sur les glaciers."
Agassiz experienced the same scepticism as many other ice-age proponents before.

"I think that you should concentrate your moral and also your pecuniary strength upon this beautiful work on fossil fishes .... In accepting considerable sums from England, you have, so to speak, contracted obligations to be met only by completing a work which will be at once a monument to your own glory and a landmark in the history of science ...[ ]...No more ice, not much of echinoderms, plenty of fish..."
Alexander von Humboldt in a letter to Agassiz on 2. December 1837

However Agassiz had good connections to the most important geologist of his time. Soon he could persuade William Buckland and later Charles Lyell. After that the most respected geologist gets convinced, the rest, as always, is history:

"advice - never try & persuade ye world of a new theory - persuade 2 or 3 of ye tip top men - & ye rest will go with ye stream, as Dr B. did with Sir H. Davy and Dr. Wollaston in case of Kirkdale Cave"
Edward Jackson, about an advice given by his professor Buckland in 1832

Fig.3. Reconstruction of the glacier that filled the valley of St. Amarin (southern Vosges, France), probably the first tentative reconstruction of an ice age glacier - from COLLOMB (1847): "Preuves de l´existence d´anciens glaciers dans les vallées des Vosges."

Agassiz research on the Unteraar-glacier established the foundations of glaciology; he recorded the dimension of the glacier, his velocity and even ventured inside the glacier by passing trough a glacial mill. Soon after 1850 the measurements methods introduced by Agassiz were carried out on various glaciers of the Alps and repeated nearly every year.

Fig.4. The Hintereis-glacier (in the centre of the picture), Hochjoch-glacier (left) and the Kesselwand- glacier, drawing by Schmetzer 1891, the Hintereis-glacier is one of the glacier with the longest active monitoring program, values about his length change reach back to 1848, since then the glacier lost 3km of his tongue.
"Aus den tiroler Alpen: Der Abschluß des Oetzthales mit dem Hochjochgletscher (links), dem Hintereisferner (in der Mitte) und dem Kesselwandferner (rechts oben). Nach der Natur gezeichnet von K. Schmetzer (1891)."

These records showed various fluctuations, but from 1850 onward a general trend of recession of glaciers in the Alps is observable. This trend has experienced a strong increase in the last 50 years, causing concern for the fast change in the landscape, the destabilisation of the rock walls once supported by the melting glaciers and the alteration of the discharge and hydrology of mountain ranges.

Fig.5. Temperature rise in the Alps and length loss of the glaciers of the Ötztaler Alps (western Austria) in the period 1900-2010. The valley glaciers with their tongues extending in the valleys showed the strongest retreat and degradation of the studied Austrian glaciers.

Geology and Cyclicity: Milankovitch´s idea

"I do not think that's my duty to teach to the ignorant the most basic things, and I have never forced anyone to accept my theory, on so far nobody could expose something."

Milutin Milankovitch in 1950

Milutin Milankovitch (1879 - 1958) was born in a relatively wealthy Serbian family, so it was almost a kind of obligation for him to archive a higher education degree and later take over the family business. So he studied agriculture, but following a passion for natural sciences he went to Vienna, where he in 1904 concluded his studies as an engineer.
Five years later he returned to Belgrad where he found employment as professor for mathematical studies at the University. Like Croll he was in search of a scientific problem worth his efforts, and in 1911, sharing some presumably good wine with a friend, he decided to develop a mathematical theory to explain climate changes on the planets of the solar system.

He studied the work of Croll, recognized his previous achievements but also noted his insufficient data. Milankovitch also consulted the work of the German mathematician Ludwig Pilgrim, who in 1904 published exact calculations of the orbital eccentricity, earth's obliquity and the rotation of the axis of earth (change of the perihelion). Pilgrim also tried to correlate the eccentricity with the occurrence of ice ages.
Between 1912 and the beginning of World War I Milankovitch published some preliminary abstracts of his developing theory, concluding that all three factors, in contrast to previous authors, are important to explain earth's climate. At the beginning of the War, Milankovitch was arrested as Serbian officer and imprisoned in his hometown Daly, but fortunately he was carrying with him his work, and so even in the first night as prisoner he continued to work. "When after midnight I looked around in the room, I needed some time to realize where I was. The small room seemed to me like an accommodation for one night during my voyage in the Universe."
Soon after he was released and travelled back to Belgrad, where he continued his work during the entire War and published some ideas about the climate of Mars and Venus.

Finally he published his theory in 1920 "Mathematische Theorie der durch Sonneneinstrahlung ausgelösten Wärmephänomene" (Mathematical theory of thermal phenomena caused by solar radiation).

Fig.1. Variations in the Earth's orbital parameters:
1. Eccentricity: the shape of the orbit around the sun.
2. Changes in obliquity: changes in the angle that Earth's axis makes with the plane of Earth's orbit.
3. Precession: the change in the direction of the Earth's axis of rotation, i.e., the axis of rotation behaves like the spin axis of a top that is winding down; hence it traces a circle on the celestial sphere over a period of time.
Together, the periods of these orbital motions have become known as Milankovitch cycles. These parameters influence the amount of solar energy on earth´s surface, especially during summer of the northern hemisphere (55°-65°N).

In his theory he postulated:
- Glaciations are caused by variations of astronomical parameters
- The parameters influence the amount of solar energy on earth´s surface, especially during summer of the northern hemisphere (55°-65°N)
- It is possible to calculate these changes, and so calculate the climate in the past.

The German meteorologists Wladimir Köppen and Alfred Wegener supported the new theory, and noted the apparent coincidence of the calculated curve with the by Penck and Brückner postulated four European glaciations.

Fig. 2. Figure from KÖPPEN & WEGENER 1924, where they correlated the calculated cycles to the know ice ages at that time.

Fig.3. Outcrop of the Trubi-Formation at Capo Spartivento (South-Italy), a succession of Globigerina-marls from the Pliocene-Pleistocene transition. The regular stripes are caused by organic rich layers, thought to be caused by changes in the biological productivity in response of changes of the astronomical parameters - the Milankovitch cycles.

References:

CHORLTON, W. (ed) (1985): Ice Ages (Planet Earth). Time-Life Books: 176
KÖPPEN, W. & WEGENER, A. (1924): Die Klimate der geologischen Vorzeit. Borntraeger, Berlin: 256

Resources:

NASA Earth Observatory: Milutin Milankovitch (1879 - 1958). Accessed 26.06.2010

Geology and Cyclicity

1842, 5 years after Agassiz's "Discourse of Neuchatel", the French mathematician Joseph Alphonse Adhémar elaborated a hypothesis to explain a cyclic occurring of ice ages. He calculated the variations of the "direction" and declination of earth axis and the "movements" of earth around the sun during the geological past.
These cyclic factors influence the time and the energy density of solar radiation that reach earth from sun, causing cyclic climatic change. Adhémar proposed that in a period of 11.000 years the hemisphere that experiences a longer winter, resulting from these three astronomical factors, would develop in an ice age.
But in 1852 Alexander von Humboldt noted that Adhémar didn't consider an important factor in his calculations, even if one hemisphere experience lower radiation, the opposite hemisphere experience an increase, so in the end the total sum remains more or less identical.

Nevertheless the idea of the French mathematician was intriguing, and would influence later researchers.

In 1833, James Croll (1821-1890), son of a poor stonecutter of Perthshire, purchased a copy of the "Penny Magazine", a magazine for children education. He was fascinated and began extensively to read, and some time later acquired he's first books dealing with natural science; "At first I was totally confused, but then the beauty and simplicity of the ideas provided me with delight and surprise, and I began seriously to study the matter."

Croll had no easy living in the next 20 years; he travelled the country, most time working as casual labourer, and in 1850 managed (for a brief time) the only Scottish pub were no alcohol was allowed.
He then found work as a maintenance supervisor of the Andersonian College in Glasgow, where he had access to the library and the hosted scientific works, a knowledge resource that he grateful exploited.
"At that time, the question of what could have triggered the ice age was much discussed among geologists. So in the spring of 1864, I directed my attention to this topic."
From 1864, Croll corresponded with Sir Charles Lyell, on links between ice ages and variations in the Earth's orbit. This led to a position in the Edinburgh office of the Geological Survey of Scotland, as keeper of maps and correspondence, where the director, Sir Archibald Geikie, encouraged his research. He also corresponded with Charles Darwin on erosion by rivers.

Croll, based on observations of the astronom Urbain Jean Josef Leverrier, used in his calculations an important factor that Adhémar did not know, the "movements" of the perihelion and aphelion on earth's ecliptic (precession of the equinoxes). He published his research in the book "Climate and Time, in Their Geological Relations" in 1875.

Fig.1. Glacial and interglacial conditions when eccentricity is at its superior limit, from CROLL1875, frontispiece (from FLEMING 2006).

Fig.2. Variations in the earth's orbit for three million years before 1800 A.D. and one million years after it, from CROLL 1875, following p. 312 (from FLEMING 2006).

Geikie wrote about the work of Croll: "The astronomical theory seems to me the best solution to the present ice age riddle. It bears in it all the decisive factors for the occurrence of alternating cold and warm periods, and accounts for the peculiar character of glacial and interglacial climates."

But there was a problem, even if dating methods at these times were only approximate, geological evidences supported a very young age of glacial deposits, but after Croll´s theory the last glacial period had ended 80.000 years ago. When Croll died, highly respected, geologists considered his theory wrong.
Geikie resumed: "It may well be, that with certain modifications of his views; one day we will solve the secret. But for now we must be continue to work and wait."

The modifications as hoped by Geikie will come only years later, and a glass wine will be the first step to solve the problem of the cyclicity of glacial periods: Geology and Cyclicity: Milankovitch´s idea.

Fig.3. Orbitally forced cyclic sedimentation in the Trubi Formation of Zanclean age at Scala dei Turchi, in the Rossello composite section (Sicily), that represents the template for the Pliocene Series.

Fig.4. Orbitally forced cyclic sedimentation as expressed in the uppermost part of the Trubi Formation and in the overlying Monte Narbone Formation at Punta Piccola (Sicily), where the Piacenzian GSSP has been defined.

References:

CHORLTON, W. (ed) (1985): Ice Ages (Planet Earth). Time-Life Books: 176
CROLL, J. (1875): Climate and Time, in their Geological Relations. A theory of secular changes of the Earth's Climate. D. Appleton and Company, New York: 630
FLEMING, J.R. (2006): James Croll in Context: The Encounter between Climate Dynamics and Geology in the Second Half of the Nineteenth Century. History of Meterology 3: 43 - 54

Megafauna Methane collapse

There are lots of hypothesis dealing with the extinction of the Pleistocene Megafauna. Now 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.

References

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

The hard life of being geologist - An introduction

150 years ago the practical work of geologists in the field was considerable different to modern standards (at least in Europe), there were differences in the equipment, but also differences in the circumstances of exploring and mapping the area of interest.
These differences begins even how to reach a specific area, today with cars most regions are accessible, 100 years ago geologists used when possible the first established train connections, but most localities were only to approach with carriages or by walking.
Because these voyages were expensive, geologist used to save time and money and after arrival in the designated study area stayed in the field for months during the entire summer. To map a larger area, most time early geologists established a base camp where heavy equipment was stored. From this base camp they started in the field, sometimes for days, sleeping in farms, cottages or under the sky.

It was a very physical work, for example the Austrian geologist Marcus Vinzenz Lipold mapped in 1853 in only one day the area surrounding the Großglockner (3.797m), and starting from the village of Ferleiten (1.151m), reached the Erzherzog-Johann-Hütte (3.454m), and finally descended back to the village of Heiligenblut (1.188m) - a heigth difference of 2.700m and a linear distance of 28 kilometres.

Every geologist of the Austrian Geological Survey carried during field exploration the standard equipment: maps and a plate to draw on with a tripod, two barometers, pocket-compass, a common telescope and a telescope with incorporated compass, psychrometer (a tool to determinate the humidity of air), thermometer and a camera obscura (an ancestor of modern digital cameras). To these tools we have to add hammers of various sizes and a portable drill.

Fig.1. "Geognosts" around 1800.

The equipment underscores the broad "uses" for geologists. Because natural science wasn't yet so specialized as today, and geology itself not so clearly delimited against other scientific fields, from a geologist it was also demanded that he possess know-how in meteorology, palaeontology, mineralogy, archaeology, botany and ethnology.
The geologist Johann Czjzek in 1850 describes the requests to be a geologist: "To every geologist mister Wilh. Haidinger, as head of the department, recommended these instructions; not only to carry out their geological tasks, but also to collect a broad variety of minerals, rocks, fossils and measurements, if these are related to science and regional and cultural studies, especially physical, geographical, historic, archaeological and ethnographic data, which connect the fossil world with the beginnings of our own history."

Fig.2. Some of the most famous geologists of the Geological Survey of Vienna (ca. 1860).

I will post these contributions parallel on a specific created blog: History of Geology.

References

GSTÖTTNER, M. (1999): Ausrüstung und Leben der frühen Geologen im Gelände. In: Geologische Bundesanstalt (ed.), Die Geologische Bundesanstalt in Wien - 150 Jahre Geologie im Dienste Österreichs (1849-1999). Böhlau Verlag. Wien.

Mount St. Helens: 30 years of posteruption glacier development

Fig.1. Glaciers in the crater of Mount Saint Helens. The Crater Glacier is shaped in a horseshoe around the new domes that have developed in the crater. The west lobe of the glacier is visible in the bottom right and two more rock glaciers can be seen to the left of the east lobe (from Wikipedia).

On May 18. 1980 Mount St. Helens landslided/exploded and lost up to 400m in height, and the geoblogosphere is celebrating the event, so must I, not necessarily focusing strictly on the gone mountain, but with a glacier related post.

With the explosion, most of the glaciers surrounding the 2.950m high peak got annihilated. The ice was in part disintegrated or melted and provided huge amounts of water for the lahars, a part of the ice detritus also got embedded in the hot volcanic ash and evaporating suddenly, exploded and created a cratered landscape.

Fig.2. Mount St. Helens before the May 18, 1980, eruption, showing location and aerial extent of glaciers (modified from Brugman and Post, 1981), from SCHILLING et al. 2004.

Prior to the eruption, 13 small glaciers with a combined surface area of about 5km2 existed on the volcano. From these glaciers the Loowit and Leschi glacier were completely destroyed, and the other glaciers suffered major mass lost.

5 years after the eruption first permanents snow patches were observed in the area between the central dome and the remaining crater walls, these patches in the following years continued to grow, feed by abundant precipitations during wintertime, avalanches and the shadow of the steep walls and protection by isolating rock detritus. In 1996 a small glacier was born, and many names were proposed for it: Amphitheatre Glacier, Crater Glacier, Tulutson Glacier, Spirit Glacier and Tamanawas Glacier, finally it was decided that the youngest glacier of the United States should be named Crater Glacier.

Fig.3. Extent of ice on Mount St. Helens. Area in white shows location and extent of glaciers as of September 2001. Glacier area, inside the crater, is about 1 km2, whereas the glacier area outside the crater is 0.52 km2, from SCHILLING et al. 2004.

Crater Glacier after 20 years of growing is today the largest of the remaining glaciers on Mount St. Helens, with an area of 1km2, thickness of 200m and a volume of 120 million m3.

The fast development and young age of various small rock glaciers inside the crater is also very intriguing.

References:

SCHILLING, S.P.; CARRARA, P.E.; THOMPSON, R.A. & IWATSUBO, E.Y. (2004): Posteruption glacier development within the crater of Mount St. Helens, Washington, USA. Quaternary Research 61: 325-329

They say that reading rocks is hard to do...

Ever wonder how to tell if a rock layer is right-side-up or turned by mountain building? Dr. Richard Alley has the answers !

Te Pito Te Henua: Botanical Investigations from the navel of the world

The collapse of the civilisation on Easter Island, or Rapa Nui in the native language, became very popular with the film "Rapa Nui" (1994) and the book of the American biologist Jared Diamond "Collapse - How societies choose to fail or survive" (2005). After the proposed reconstruction in both film and book, human population growth and overexploitation of natural resources, especially clearing of forest, caused soil degradation and resulted in diminished agriculture production, not able any more to feed the population. In the resulting famine and civil wars one of the highest developed cultures in the Pacific Ocean collapsed.

Fig.2. Map of Easter Island, or Rapa Nui / Te Pito Te Henua (Navel of the world) with the mentioned localities (after THOMSON 1891).

This scenario is based primarily on the discovery during an archaeology expedition prior to 1961 of unknown palm-like pollen in sediments, on an island today lacking completely any native tree species. In subsequent years further cores were analysed for pollen, also root imprints in soil and subfossil nuts found in caves supported the claim that the island was covered by a forest in past times.

Fig.3. Rongorongo, the unique "scripture" of Rapa Nui is still a mystery. The displayed symbol is interpreted to represent or be inspired by a palm tree (after THOMSON 1891).

Today Rapa Nui is covered by meadows (90%), planted Eucalyptus trees (5%), shrublands (4%) dominated by invasive plant species and pioneer and urban vegetation (1%).

Until today the number of studied cores to reconstruct the paleoecology of the island is limited, and most were analyzed with a very coarse resolution and present mayor sedimentary gaps, so many doubts remain how fast and when Rapa Nui lost entirely it´s forests.
According to recent palynological studies the island experienced a cold and dry climate until the end of the last glacial maximum ca. 12.000 years BP, then during the moister climate of the Holocene the forest expanded and persisted until the arrival of Humans AD 800 to 1200. Deforestation then presumably took place between these ages and the arrival of Europeans in 1800 AD.

There exist two major categories of hypothesis to explain the massive destruction of plant live and lose of species diversity on the island. Some hypothesis, summarized in the book "Collapse", impute deforestation to direct and indirect human behaviour, clearing of the forest until the last tree and/or introducing invasive plant or animal species, that concurring with native species caused their extinction. Other hypothesis, more speculative, deal with a possible massive impact of past climate changes.

Fig.4. Pictures of the three volcanic craters with continuous cores used for pollen analysis. A) Rano Aroi, B) Rano Kao and C) Rano Raraku (photos by V. Rull from RULL et al. 2010).

Sediment records of the island past can be obtain from the swamps and lakes situated in the larger craters of the volcanic island, because larger sediment traps are more likely to hold thicker and undisturbed sediments. Rano Aroi crater holds a bog with an outflow and connections to the groundwater table. Rano Raraku and Rano Kao craters hold permanent lakes without outflows and are disconnected from the main groundwater bodies by impermeable lacustrine sediments.

The count of pollen grains in sediment recovered from a core of the lake Ranu Raraku shows a replacement of palm-dominated by grass-dominated pollen assemblages in the sedimentary record as of 1200 AD.

Fig.5. Percentage pollen diagram from Rano Raraku compared to charcoal concentration in the analyzed sediment. The calibrated C14 ages show a major gap in sedimentation between 800 and 4.000BP. The decline of palm pollen and increase in charcoal (a proxy for anthropogenic induced fires) happens shortly after this presumed gap (from MANN et al. 2008).

Unfortunately interpretation of pollen diagrams can be very tricky.
Pollen sum curves do reflect a relative change in pollen production, which not necessarily reflect the absolute number of palm trees in the surrounding. Depending on the tree species, and if it is pollinated by animals or by wind, different species can produce very different quantities of pollen. To correct this error a calibration factor must be known.

The tree species that produced the pollen on Rapa Nui is unknown. Pollen-morphological similarities exist to widespread species on pacific islands like Pritchardia, Cocos (coconut) and Jubaea chilensis (wine palm). But sparse macroremains, like the damaged nuts, seems to discard all mentioned species (assuming that all known remains like roots, pollen and nuts represent only one species), and are more similar to the nuts of Juania australis, an endemic palm species on the Juan Fernández Islands.
Based on these remains finally the extinct species Paschalococos disperta, with dubious systematic affinities to recent tree species, was established. So the pollen calibration factor for the extinct species can not more obtained.

The pollen signal conserved in the bog also depends strongly from the location of trees in the catchment. Few trees very near the shore of a lake can give stronger signals that many trees located in great distance.

On Easter Island the sedimentological records shows a prominent gap in the last centuries and millennia, maybe as result of a major drought and dry out of the studied lakes, unfortunately just in the time where the strongest human impact is postulated.
In the end pollen records can give only approximately ages of vegetation changes occurring between 1900 and 600 years BP, but not the extent and cause of such changes.

The number of former palm trees on the island was estimated by density of root imprints to 16 million, covering up to 70% of the surface. But these numbers are in contrast to the small amount of charcoal or wood fragments recovered until now on the island., It is however possible that the missing wood-debris and charcoal was eroded, transported and deposited in the surrounding ocean.

Considering the mentioned problems arising from the reconstruction of the former vegetation by means of pollenanalysis, the observed pollen data can also be explained by the presence of sparse forest patches or small numbers of trees growing near the shores of the studied lakes or on steep slopes, until finally the arrival of Europeans and their cattle and goats finished off the last survivors.

The intriguing questions remains, did the former inhabitants lumber completely the island's dense subtropical forest to still their megalomaniac hunger for bigger and bigger moai, and finally caused their own demise, or was Rapa Nui since the beginning of human colonization a sensible and tree poor ecosystem, and climatic causes like a drought combined with human impact caused an inexorable collapse?
The available botanical data still don't allow an exclusion of one or the other scenario.

References:

THOMSON, W.J. (1891): Te Pito Te Henua, or Easter Island. Report of the National Museum 1888-89, Smithonian Institution. Washington
RULL, V.; CANELLAS-BOLTA, N.; SAEZ, A.; GIRALT, S.; PLA, S. & MARGALEF, O. (2010): Paleoecology of Easter Island: Evidence and uncertainties. Earth-Science Reviews 99:50-60 doi:10.1016/j.earscirev.2010.02.003
MANN, D.: EDWARDS, J.; CHASE, J.; BECK, W.; REANIER, R.; MASS, M.; FINNEY, B. & LORET, J. (2008): Drought, vegetation change, and human history on Rapa Nui (Isla de Pascua, Easter Island). Quaternary Research 69:16-28 doi:10.1016/j.yqres.2007.10.009 Fulltext (pdf)

Introductory Picture from Wikipedia

The first geological map depicting loess (1865)

Loess is silt dominated sediment with minor amounts of sand and clay. This homogenous particle distribution is a result of the formation of the up to hundred of meters thick massive deposit; it's a terrestrial, windblown sediment, most time with homogenous bright, yellowish colour. Primary sedimentary structures in loess are subtle, so the true origin of this sediment was for a very long time unclear. Lyell in his first editions of Geology books interpreted loess as fluviatile loam.*

Loess covers a significant amount of the Earth's land surface, perhaps as much as 10%. Because of its widespread distribution, texture and mineralogy, it forms some of the world's most important agricultural soils.
There exist two main models to explain the formation and distribution of loess. The classical hypothesis interpret it as primarily glacial eroded and reworked material, from where the finer fractions become subsequently selective transported and accumulated by wind. The second model explain the main source of the windblown material to coming from deserts or arid areas, not necessarily related to glaciers, as a result of dry climate conditions during glacial periods.

Fig.1. Carl Maria PAUL, Guido STACHE and in the middle Franz Ritter VON HAUER, the author of the first loess map of Central Europe.

The geologist Franz Ritter von Hauer was the second Director of the Geological Survey in Vienna (1866-1885). One of his main contributions to Quaternary science was the geology textbook of the former Austro-Hungarian Monarchy, which provided a resource to access recent developments in geology and notably loess research to many scientists. In the middle of the 19th century he also coordinated the geological mapping of the monarchy, initiated mainly for economical reasons to record the mining activities and map future potential mineralogical resources.
Even if quaternary sediments were not the primary interest of the project, Hauer tried to establish a first approach to mapping and classification of these deposits.

Fig.2. The second edition of the General Geological General Map of the Austro-Hungarian Monarchy compiled by von Hauer (Archive of the Austrian Federal Geological Survey) compare to Fig.4. for the loess formation (mainly yellow and ligth green coloured area), from GAUDENYI & JOVANOVIC 2010.

Fig.3. Enlargement of the map in Fig.2.

The General Geological Map of the Austro-Hungarian Monarchy presented in 1865, and produced between 1850 and 1856, was one of the most comprehensive and complete geological map of Central Europe during that period of time.

The Quaternary formations were subdivided in two groups: Pleistocene and Holocene formations. The Pleistocene formations identified as "Dilluvial" included predominantly fluvial gravels and sand, but also loess. The Holocene formations were denominated "Alluvial" and included peat, lime tuff, quicksand and other formations summarized only as "Alluvial formations".
Loess was mentioned exclusively as a Pleistocene ("Dilluvial") formation and the distribution clearly outlined, even if, for lack of detailed knowledge, the definition differs from the modern understanding of loess . In the Austrian geological map for example, the loess formation in some areas also included "loess-like" sediments, as for example colluvial deposits.

Nevertheless it was one of the first maps which documented the extent of loess deposits in Europe and West Asia.

Fig.4. Modern map of loess distribution, from HAASE et al. 2007.

*The Student's Elements of Geology (1870): "In some parts of the valley of the Rhine the accumulation of similar loam, called in Germany "loess," has taken place on an enormous scale [several hundred feet thick]. Its colour is yellowish-grey, and very homogeneous; and Professor Bischoff has ascertained, by analysis, that it agrees in composition with the mud of the Nile. Although for the most part unstratified, it betrays in some places marks of stratification, especially where it contains calcareous concretions, or in its lower part where it rests on subjacent gravel and sand which alternate with each other near the junction. Although this loam of the Rhine is unsolidified, it usually terminates where it has been undermined by running water in a vertical cliff, from the face of which shells of terrestrial, freshwater and amphibious mollusks project in relief. These shells do not imply the permanent sojourn of a body of freshwater on the spot, for the most aquatic of them, the Succinea, inhabits marshes and wet grassy meadows."

REFERENCES:

GAUDENYI, T. & JOVANOVIC, M. (2010): Franz Ritter von Hauer's work and one of the first loess map of Central Europe. Quaternary International. 10.1016/j.quaint.2010.04.008
HAASE, D., FINK, J., HAASE, G., RUSKE, R., PECSI, M., RICHTER, H., ALTERMANN, M., JÄGER, K. D. (2007): Loess in Europe - its spatial distribution based on a European Loess Map, scale 1:2,500,000. Quaternary Science Reviews 26 (9-10), 1301-1312