Featured Research

from universities, journals, and other organizations

Turkey's Lake Van Provides Precise Insights Into Eurasia's Climate History

March 15, 2007
University of Bonn
The mud at the bottom of Turkey's Lake Van stores information about the climate of the last 500,000 years. Millimeter-thin layers with embedded pollen reveal climate information with a year by year-resolution.

Grains of pollen sink to the bottom on the lake each summer and provide information on the climate of the region. The pollen of yarrow appears prickly and is easy to identify.
Credit: Prof. Dr. Thomas Litt, University of Bonn

The bottom of Turkey's Lake Van is covered by a layer of mud several hundreds of metres deep. For climatologists this unprepossessing slime is worth its weight in gold: summer by summer pollen has been deposited from times long past. From it they can detect right down to a specific year what climatic conditions prevailed at the time of the Neanderthals, for example. These archives may go back as much as half a million years.

Related Articles

An international team of researchers headed by the University of Bonn now wants to tap this treasure. Preliminary investigations have been a complete success: the researchers were able to prove that the climate has occasionally changed quite suddenly -- sometimes within ten or twenty years.

Every summer an inch-thick layer of lime -- calcium carbonate -- trickles down to find its final resting place at the bottom of Lake Van. Day by day during this period millions and millions of pollen grains float down to the depths. Together with lime they form a light-coloured layer of sediment, what is known as the summer sediment.

In winter the continual 'snowdrift' beneath the surface changes its colour: now clay is the main ingredient in the sediment, which is deposited as a dark brown winter sediment on top of the pollen-lime mix. At a depth of 400 metres no storm or waves disturb this process.

These 'annual rings' in the sediment can be traced back for hundreds of thousands of years. 'In some places the layer of sediment is up to 400 metres thick,' the Bonn palaeontologist Professor Thomas Litt explains. 'There are about 20,000 annual strata to every 10 metres,' he calculates. 'We presume that the bottom of Lake Van stores the climate history of the last 800,000 years -- an incomparable treasure house of data which we want to tap for at least the last 500,000 years.'

250 metres of sediment = 500,000 years' worth of climate archives

Professor Litt is the spokesman of an international consortium of scientists that wants to get stuck into a thorny problem: using high tech equipment they want to cut drill cores as thick as a man's arm out of the lakebed sediment from a big floating platform -- not an easy task at depths of 380 metres. The researchers want to drill down to a sediment depth of 250 metres.

For this they have applied for funding by the International Continental Drilling Programme (ICDP). This would be the first time that an ICDP drilling was headed by a German. The prospects of this happening are not bad. A preliminary application was assessed as very good by the ICDP Executive Committee -- above all thanks to a successful preliminary investigation which the researchers had carried out at Lake Van in 2004. The German Research Council (Deutsche Forschungsgemeinschaft, DFG) financed this. It has just extended the project for two more years.

The sediment promises to deliver a host of exciting results. For example vulcanologists can determine exactly when volcanoes near the lake erupted. In this case there will suddenly be a black layer of ash between the annual layers. 'With our test drill we counted 15 outbreaks in the past 20,000 years,' Prof. Litt says. 'The composition of the ash even reveals which nearby volcano it originates from.'

Chubby-cheeked pollen

Even earthquakes in this area of high geological activity are painstakingly stored in these archives. What is the most interesting aspect for Thomas Litt, however, is the biological filling contained in the summer layers, especially.

The microscopically small pollen tells the palaeobotanist what sorts of things used to flourish on the shores of the lake. In a piece of sediment the size of a sugar cube up to 200,000 grains of pollen can be trapped. Under the microscope the fine dust reveals a very special kind of beauty. The pollen of yarrow is as prickly as a hedgehog, the pollen of pine with its air sacs resembles the chubby-cheeked face of a hamster, 'and look at the olive tree,' Professor Litt enthuses, 'it's also got a very nice pollen grain.'

The researcher normally recognises at once what genus or species the finds belong to -- even when they are several thousands of years old, since the exine, the outer coat of the grain, successfully resists the ravages of time. 'The material is extremely resistant to environmental influences and even withstands strong acids or bases,' Professor Litt explains.

Using hydrofluoric acid or potassium hydroxide he dissolves the pollen grains from the sediment samples; the grains prove to be completely impervious to such rough treatment. Under the microscope the botanists then assess how much pollen of which species is present in the layer in question. 'At interesting points we take every centimetre of material from the drill cores; in this way we achieve a chronological resolution of a few years.'

The pollen permits pretty precise statements to be made about temperature and average amount of precipitation for the period covered by the finds, as every species makes different demands on its environment. 'If we find pollen in a specimen from different species, whose demands on its habitat are known, we can make a plausibility statement about the nature of the climate of the time,' he adds. 'Lake Van promises to provide unique insights into the development of the climate in Eurasia -- and thus for assessing the current warm period.'

Story Source:

The above story is based on materials provided by University of Bonn. Note: Materials may be edited for content and length.

Cite This Page:

University of Bonn. "Turkey's Lake Van Provides Precise Insights Into Eurasia's Climate History." ScienceDaily. ScienceDaily, 15 March 2007. <www.sciencedaily.com/releases/2007/03/070314110552.htm>.
University of Bonn. (2007, March 15). Turkey's Lake Van Provides Precise Insights Into Eurasia's Climate History. ScienceDaily. Retrieved April 17, 2015 from www.sciencedaily.com/releases/2007/03/070314110552.htm
University of Bonn. "Turkey's Lake Van Provides Precise Insights Into Eurasia's Climate History." ScienceDaily. www.sciencedaily.com/releases/2007/03/070314110552.htm (accessed April 17, 2015).

Share This

More From ScienceDaily

More Fossils & Ruins News

Friday, April 17, 2015

Featured Research

from universities, journals, and other organizations

Featured Videos

from AP, Reuters, AFP, and other news services

Cleaners Find Ancient Peru Mummy

Cleaners Find Ancient Peru Mummy

Reuters - News Video Online (Apr. 15, 2015) Cleaners in Peru stumble across an ancient mummy mysteriously dumped near rubbish in the pre-Incan city of Chan Chan. Rough cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
388 Unidentified Pearl Harbor Victims To Be Exhumed, ID'd

388 Unidentified Pearl Harbor Victims To Be Exhumed, ID'd

Newsy (Apr. 15, 2015) The Department of Defense is exhuming the unidentified remains of 388 servicemen who died on board the USS Oklahoma in 1941. Video provided by Newsy
Powered by NewsLook.com
Manuscript by Nazi Code Breaker Alan Turing Sells for $1 Million

Manuscript by Nazi Code Breaker Alan Turing Sells for $1 Million

Reuters - Light News Video Online (Apr. 13, 2015) Alan Turing&apos;s notebook containing the foundations of mathematics and computer science sells at auction for $1,025,000 (USD). Roselle Chen reports. Video provided by Reuters
Powered by NewsLook.com
Replica Cave Showcases Artistry of Stone Age Man

Replica Cave Showcases Artistry of Stone Age Man

AFP (Apr. 10, 2015) A replica of a cave in the Ardeche, in southern France will be opened Friday to give visitors the chance to see cave paintings produced around 36,000 years ago. Duration: 01:05 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.


Breaking News:

Strange & Offbeat Stories

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News


Free Subscriptions

Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile

Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?

Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins