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VENTIFACTS

 
VENTIFACTS

Page Type: Album

Object Title: VENTIFACTS

Image Type(s): Informational, Scenery

 

Page By: Romuald Kosina

Created/Edited: Jan 29, 2010 / Feb 15, 2010

Object ID: 592822

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Page Score: 82.48% - 15 Votes 

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Ventifacts are witnesses of local or very distant mountains…

 
Melting of...
 
 
Rapakivi...
 
 
Fragment of ...
 
 
Fragment of ...
 

Large continental glaciers covered in the past the surface of our planet. Also Central Europe was completely frozen by such a glacier stretched from the north and Scandinavia toward the south. Maximum of the last Pleistocene glaciation was about 19,000 years ago. Another short cold period occurred in Europe between 1550 and 1850 and is called the Little Ice Age. Huge mass of ice transported boulders and stones from the Scandinavian mountains, e.g. to Poland, and deposited them as erratics. These stones lying on an open surface were originally sculptured by wind-driven sand and crystals of ice or by directional activity of glacial waters carrying small debris of rocks. A stone surface exposed through a log time to these wind and water attacks has been eroded and polished. This phenomenon is called abrasion and is also common in deserts. The ventifacts in deserts are of local origin. After polishing this surface was outlined by distinct edges creating a facet. When the direction of wind or water has been changed, another side of the stone was smoothed. Finally, such stones originally shaped have several flat facets.
These stones are called ventifacts (in Latin ventus = wind) or dreikanters (a stone having most often three edges).
Sometimes their shape was so spectacular that they were used by our neolithic ancestors as stone tools. It is not easy today to distinguish some natural ventifacts from artefacts made by man.
Scattering of ventifacts in a glacial deposit is not random but characteristic for a given site. It is a result of the selective and accumulative role of glacial waters.
In this album the ventifacts, witnesses from the Scandinavian mountains, were collected in the western vicinity of Wrocław, my home city. They origin from the mother mountains composed of different rocks, igneus, sedimentary and metamorphic.
Some ventifacts were documented together with other the same stones for size comparison. The less visible edges on ventifacts are marked by lines.

I hope this album will increase our knowledge on mountains...

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