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

Biggest Beaver Dam Ever

The actual location of the world longest beaver dam (that is until someone find a longer one) is just south of Lake Claire, about 190 km to the NNE of Fort McMurray, inside Wood Buffalo National Park, Northern Alberta- Canada.
The dam has a length of about 850 meters and It has at least existed at this spot for over 15 years , aerial photo's show that this dam did not exist in 1975.

Fig.1.