Geotrail Nov 2019

Geoweek was organized from 18th to 23th November 2019 on the overall theme “Earth Science Matters”. As part of the Geoweek, a Geotrail was organized on 23rd November 2019.

Geotrail comprises of day long guided field trip to easily accessible outcrops, in and around Pune district, Western Maharashtra. As the entire area is covered by ~64-66 Mya Deccan Volcanics, the Geotrail is designed in such a way that it highlights the morphological features of the different lava flows, other physical volcanological features like lava tubes, lava caves, lava channels and various geomorphic features carved in the volcanics such as natural Arch/bridge, potholes etc.

The Geotrail 2019 included visits to some of the sites in the Deccan plateau region, northeast of Pune like Nighoj, Gulunchwadi, Wadgaon Darya & Kanherwadi. Twenty-one persons from different age groups participated in the Geotrail. Our first stop was along the Ane ghat road, close to Gulunchwadi. The ghat road exposes two basalt flows, intruded by a dyke. Adjacent to the roadside temple is a stairway that leads to the stream below, where we can see a natural arch. The stream- Ardhara Nala, a tributary of Kukadi river is fracture controlled. As a result of erosion along the fractures and groundwater sapping along the flow contacts the pathway of the stream was enlarged. Further downcutting, and rock fall from the roof, has given rise to the Natural Arch we see today.

We proceeded north to Mandohal Dam and from there, further northwest to Kanherwadi/or Masobajhap. The sinuous ridge like topography seen is an exhumed lava channel, much like a river of lava, that erupted 67-66 million years ago. One can see formation of lava channels in the recent eruptions in Hawaii and Iceland. Downslope it branches into distributaries. The rocks at the margins are reddish in colour, more fine grained and glassy. The iron in the matrix imparts the rick red color to the rock. Often the margins are fragmented, and the interspaces are filled with secondary minerals like scolecite, silica and calcite.

After a quick lunch at Karjule, we headed south to Daryabai Temple near Wadgaon Darya, where stalactite formation can be seen. From here we travelled to Nighoj, a place famous for giant potholes. The potholes are developed in the Kukadi river-bed. The flows exposed here are of compound pahoehoe type. Potholes of varying sizes and in different stages of formation can be seen. It is truly a mesmerizing site.

All good things come to an end… As the sun set, it was time for us to return to Pune with memories of the rocks, rivers and the giant potholes … testimony to the restless Earth and the wonderful world of nature.

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