Travel Shot: Columnar basalts on Rajasthan State Highway 19A

It is about a quarter past 9 on that November morning of 2016, and we (my friend Niti and I) are on our way to visit the Buddhist rock-cut caves at Kolvi from Jhalawar, Rajasthan. A brief halt at Bhawani Mandi for a breakfast of poha, jalebi and tea later, we are more that half way into the 2 hour drive to the caves on Rajasthan State Highway 19A.

The view from the car window is of a largely flat countryside lit up in the wintry sunlight. We pass village settlements, farmlands, a river crossing… all in all very peaceful and idyllic.

Suddenly Niti asks, “What’s that?”

I’m seated behind the driver and have to twist to look at what she is pointing at on her side of the road.

And as soon as see it, I tell the driver, “Stop. The. Car. NOW.”

Manoj, our driver, not only stops the car, but reverses it so that we can get a better look. At any other time, I would have chided him for reversing on a highway, but at that point in time all I could do was to wait impatiently for him to stop and the jump out of the car to get a better look.

“What are we looking at?” asks Niti.

“This, my friend, is what is known as columnar jointing in rocks,” I say. And add with a touch of drama, “There aren’t many sites like this; I know of only two in India.”

Travel, Kolvi, Rajasthan State Highway no. 19 A, Columna Basalts, Columnar jointing, Travelling Geologists, Igneous rock, Geological Structure, Igneous structure. Deccan Basalts, Magma Chamber
The view from Rajasthan State Highway 19A

The road is at an elevation and there’s a short, but steep, descent to get down for a closer look. My first good look at the exposure reveals that it extends on both sides for as far I can see.

Travel, Kolvi, Rajasthan State Highway no. 19 A, Columna Basalts, Columnar jointing, Travelling Geologists, Igneous rock, Geological Structure, Igneous structure. Deccan Basalts, Magma ChamberA board announces that the land is owned by a quarrying company. Going by the number of broken columns everywhere and the area covered by them, the quarrying must have been going on for quite a long time. There is, however, no quarrying activity — in fact, there is no one around — happening then, so I take my time to have a good look around.

The first thing I do is to confirm if the rock is a basalt. A fresh exposure of a fine-grained, dark, almost black coloured, rock — behind the bleached, light coloured exposure — confirms my guess.

Travel, Kolvi, Rajasthan State Highway no. 19 A, Columna Basalts, Columnar jointing, Travelling Geologists, Igneous rock, Geological Structure, Igneous structure. Deccan Basalts, Magma Chamber
Remnants of quarried ‘waste’ lie in the foreground, even as the rock columns in the background wait for their turn to be extracted.

As I walk around site, I recall my undergrad classes in Geology on jointing patterns and fractures in rocks.

Columnar joints are a specific type of joint pattern found in basaltic lava flows that create parallel, prismatic or hexagonal columns as a result of differential cooling. As the basalt cools rapidly from the outside toward the centre, this causes cracks to form, commonly, in a hexagonal pattern, creating columns of basalts that can range from a few inches to several feet in diameter as well as a few feet to tens of feet in height.

Travel, Kolvi, Rajasthan State Highway no. 19 A, Columna Basalts, Columnar jointing, Travelling Geologists, Igneous rock, Geological Structure, Igneous structure. Deccan Basalts, Magma Chamber
These columnar basalts are massive; just look at the cow on the top left for scale. Also note the hexagonal shape of the columns

I wonder about the origin of these columnar basalts. Are they part of the original spread of the Deccan Basalts or are they an unconnected assemblage of rocks?

I also wonder if there are local stories and folk tales around these columnar basalts as it is in Ireland where they are believed to have been made by giants.

I wonder about the little orange shrine built on the site. Was it built by the quarry workers or is it an older shrine?

Travel, Kolvi, Rajasthan State Highway no. 19 A, Columna Basalts, Columnar jointing, Travelling Geologists, Igneous rock, Geological Structure, Igneous structure. Deccan Basalts, Magma Chamber
The orange painted shrine makes for a rather dramatic pop of colour against the soaring columns of basalt.

I also wonder at the sheer luck, and the chance sighting of these rocks were, especially considering how uncommon their occurrence is. Three cheers to Niti, and her sharp eyes.

I felt blessed that day. 🙂


Notes:

  1. I know of two other sites in India where columnar basalts can be seen — Gilbert Hill in Mumbai and St. Mary’s Island, off the Karnataka Coast near Malpe. The former is on the verge of disappearing, thanks to quarrying and encroachment, while I had the latter place to myself when I visited St. Mary’s Island in November 1998. I believe that it is buzzing with tourists today.
  2. I have not found yet found any substantial information on these columnar basalts, and when I do, I will update the information here.

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4 thoughts on “Travel Shot: Columnar basalts on Rajasthan State Highway 19A

  1. Wow! Never had heard of basalt, leave alone columnar basalt. And really impressed with your knowledge of rocks – for remembering all those lessons all those years later 🙂

    Liked by 1 person

    1. Look out of your window, Zephyr and the hills that you see in the distance are made up of basalt. The rocks that you see on your way to Pune are Basalt.

      How can I forget my Geology lessons, Zephyr. They are a large part of who I am today. 🙂

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