Thursday, December 28, 2017

Geology Excursion To Tamhini Ghat And Korlai - India West Coast

On December 16 and 17, I took part in an excursion to the village of Korlai. This place is about 150 km west of Pune. The trip was organized by Deep Dive India, a venture started by my cousin Shirish Kher. The idea is to offer participants an immersive experience into one or two specialized fields.  On offer for this trip was geology and archaeology. I was the designated geology expert. The accompanying archaeologist was Sachin Joshi, a researcher from Deccan College Pune.

It was a lot of fun!

The group was mostly made up of working professionals with an interest in nature. Many of them came to know of this trip from my Twitter feed.  We drove westwards along the Deccan Plateau. Then, we descended the Western Ghat escarpment along Tamhini Ghat.  On this section, we made several stops to survey the landforms and to examine lava flows. I also gave the  group an introduction to Deccan Volcanism. After crossing the coastal plain we ended up at the village of Korlai, where there was more geology on offer.

We stayed in a home stay in the village of Chaul, a few kilometers away from Korlai.

The next day, Sachin Joshi gave us a fascinating walk-through the Portuguese forts at Korlai and Revdanda. These two villages are on opposite banks of the Kundalika estuary. It is quite a beautiful location. The forts were established by the Portuguese in the 1520's,  a couple of decades after Vasco da Gama rounded the Cape of Good Hope and established trading contacts with rulers and merchants of the Indian west coast.

The satellite image below shows the backwaters of  Mulshi and Varasgaon dams on the edge of the plateau, Tamhini Ghat, the coastal plain and the locations of Korlai and Revdanda villages. The sinuous N-S trending white dotted line seen along the Tamhini Ghat just west of the backwaters is the Western Ghat escarpment.

..and here are more pictures from our trip.

I gave a brief preview of the trip and explained the physiography of our traverse which took us along the Deccan Plateau, down the escarpment and to the coast along a broad coastal plain.

Along the way at Tamhini Ghat, I stopped to point out a lava flow contact. You can see pipe vesicles at the base of the upper flow.

 In Tamhini Ghat, unrolling a satellite imagery, I explained the landforms and structure of the Western Ghat escarpment to geology enthusiasts young and younger!

 At Korlai coast the group is looking down at a dike.

I demonstrated the use of a Brunton compass at this dike.

And here is a view of some of the many dikes intruding the basalts along the west coast.

The rampart and walls of Korlai fort along the rocky coast. You can see a cannon protruding through an opening in the wall.

The group standing on the surface of a lava flow showing columnar jointing. You can make out the polygonal shape of basalt blocks.

Korlai village fishing fleet moored in a back bay with the open Arabian Sea to the right. View from top of Korlai fort.

A beautiful view of Revdanda Fort, built on a sand bar, with waves crashing on to the walls and ramparts.

A watchtower in Revdanda Fort

An entrance with icons of a saint and official markings carved on stone.

 Through a broken wall of Revdanda Fort, a view of the Kunadalika estuary. Korlai Fort is on the stretch of land seen on the opposite side of the river.

The group enjoying themselves, exploring the fractured basalts of the west coast.

A picturesque home in Revdanda village.

This was the first time I had taken a group out on an organized trip like this. I was a bit nervous to begin with. But the atmosphere was informal and the participants enthusiastic and curious. That led to many long and enjoyable discussions on geology and archaeology.

We will be doing a repeat trip along the same route in late January... more pics then.

Thursday, December 21, 2017

Lamarckism Continues To Cast A Shadow Over The Archaeological Survey Of India

A friend mentioned that she was planning to visit the famous rock shelters at Bhimbetka in Madhya Pradesh. These sandstone caves are famous for rock art and stone tools ranging in age from Paleolithic to more recent times. The site is looked after by the Archaeological Survey of India (ASI).

I remembered my own trip there over three years ago. Diving into my picture collection I  came up with this gem. This plaque was in front of a cave where Paleolithic stone tools had been found. It describes the grand story of human evolution.

Underlined in yellow is the explanation for the evolution of our dexterous hands. I am not highlighting the language but the very Lamarckian-sounding mechanism. If the claim is that hands capable of making sophisticated tools evolved just by continuous handling of stone, then this is evolution occurring through inheritance of acquired characteristics. Just like a blacksmith passing on his musculature to his children. This is not a viable mechanism of evolution. Physiological changes acquired due to a life experience are not passed on to progeny. Our gametes are sequestered from our somatic cells. I strongly suspect that a lot of people still conflate inheritance of acquired characters with natural selection.

The very first sentence "Millions of  years after Ramapithecus the species Australopethecus and its subspecies came into existence" is confusing too.  As is another plaque which shows the classic linear march of hominin evolution from a more primitive looking ape to modern humans. In it, Ramapithecus appears to be an early ancestor of humans.

Australopithecus (genus, not species), did appear millions of years after Ramapithecus, but there is no ancestor-descendant relationship between the two. Ramapithecus was initially identified as a Miocene ape and a possible ancestor of humans. Its range was the Himalaya foothills, leading to some excitement that the human family roots can be traced to the Indian subcontinent. More fossil finds have changed this early interpretation. Ramapithecus is not even considered a valid taxon anymore. The fossils named Ramapithecus are now subsumed under the genus Sivapithecus. This latter genus includes a great variety of Asian ape species. The lineage is more closely related to the ancestors of the Orangutan and not to living African apes and the hominin family.

This is just a poor show by the ASI. They need to urgently upgrade the information they are providing the public.

Wednesday, December 13, 2017

Remotely India: Structural Control On Drainage

 Remotely India #10

Check out this amazing example of fracture controlled stream flow. Follow blue arrows.

The stream originates on the steep west facing slopes of Tamhini Ghat (west of Pune) and flows a north westerly course in a NW-SE trending fracture, then makes an abrupt left turn and flows south west into a NE-SW trending fracture. It then exhibits a number of right angle turns. Finally, it turns sharply and flows north along a N-S trending fracture before joining the larger Kundalika river near Mhasewadi.

This area comprising the edge of the Deccan Volcanic Plateau and the coastal plain has been shattered by several fracture systems which formed due to tensile forces affecting the western margin of India during and post Deccan volcanism.

Take some time looking at this image above. You will see scores of small streams flowing along fractures and making sharp turns at fracture intersections. The geomorphology of this part of the Deccan Volcanic Province is a joy to explore.