Lonar Crater

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Lonar crater lake is a nearly circular in shape . Its the only lake in the world formed by meteorite impact in basaltic rock. The impact is said to have come from the east side . Its ages is estimated to be older than 500 000 years .Earlier it was thought to be have been a volcanic crater but with more studies it was confirmed meteoric impact crater , like presence of maskelynite which got converted from feldspar , presence of Tectites ie pieces of molten silica ,etc.

Lonar crater is analyzed into five distinct zones :

1.The outermost Ejecta Blanket.
The ejecta topography, with a circum-rim syncline and accumulation of material at the flow terminus, is similar to layered ejecta structures on Mars(or the moon ). The basaltic layer at the impact site is approximately 400 m thick .
2. The crater rim
The rim portion has average rim height of 40 m and its rise from the ground is noticeable .The rim also protects the lake from routine winds and thus give rise to local micro weather system .
3. The slopes of the crater
It has a sharp 75 degree slope at the beginning and also confirmed to the topology of impact crater ( versus volcanic crater).It then gradually tapers to 25 to 5 degrees .
4. The crater basin, excluding lake
The Lonar Crater has an average diameter of 1.8 km and depth of 150m .Studies say that the depth earlier must have been in the range of 230 – 245 m .The mud sarounding the lake is also alkaline in nature and one can find various rock formation in this region which are unique due to the meteoric impact effect .
5. The crater lake
The circular depression in the center is a saline water lake with mean diameter of 1.2 km ,maximum depth of 5.50 meters. The lake is 137m below the crater rim. The lake water is saline and alkaline in nature The pH of water keeps fluctuating with weather .Its generally higher in summer and less in rainy season :) . The pH also varies from shore to center ,where it is in the range of 10.5 to 11 .Salinity of lake is due to dissolved carbonates (hence people refer to it as saline soda lake) .The salinity has been decreased from 300 ppt in 1958 to mere 100 ppt today . Even now you can wash your gold rings into the lake water and see the effect for yourself (however it will damage your ring as well as ecology of the lake ).

The lake water is home of many unique biological ecosystems and is matter of continuous study . Scientists have confirmed existence of nitrogen fixing ,methane eating bacteria in this water .The lake proposed to be a ‘Ramsar Site’ in India. There is another small pond like lake called amber lake in vicinity which said to have been formed from another small meteor portion but its on verge of getting extinct .

Also see

http://www.lpi.usra.edu/meetings/lpsc2007/pdf/2316.pdf

http://earthobservatory.nasa.gov/IOTD/view.php?id=8654

http://www.wondermondo.com/Best/World/ImpressiveImpactCraters.htm

http://www.china.org.cn/top10/2013-02/17/content_27978524.htm

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