Geoheritage: karst landscapes
St Mary's Island. Credits: Dilshad Roshan, CC BY-SA, Wikimedia Commons.
Geoheritage encompasses geological features that provide clues about the evolution of the Earth and its inhabitants.
These can include geographical features like glaciers, islands, deserts, volcanic landscapes (eg. Yellowstone National Park, USA), etc. Or geological formations such as wave-carved caves or arches, limestone formations, fault lines, or volcanoes (eg. Toba caldera/Anak Krakatau, Indonesia). Or fossil formations where ancient creatures are preserved between layers of sedimentary rocks (eg. The Jurassic Coast, UK).
By this definition, geoheritage can foster: Scientific interest - as sites that further our understanding of past regimes of landscape evolution, tectonic activity, river migrations, to identify mineral resources, groundwater and other water sources, or as records of human or industrial history. For this scientific, cultural and aesthetic value, such sites deserve to be recognized and conserved. Educational interest - these sites serve as windows into our past, and can be used to educate the public and raise awareness about the past and present processes that shaped the Earth. Geotourism - these sites can help inform the wider public of our patrimony, and its relevance to modern society, while enabling sites to become financially viable and sustainable as tourist destinations.
For those who are interested in knowing more, a couple of months ago, I was invited to deliver a talk on the conservation of landforms, through the lens of geology. In school, we often learned to see landforms (like islands, mountains, plateaux, caves, valleys, lakes, volcanoes, to name a few) as isolated features and defined and labelled them as distinct units of a landscape. Yet landforms are not mere monuments, they provide clues to the past processes that shaped landscapes, and can offer insights into how the present processes work too. Landforms are the remnants, the clues to the Earth's past, and to truly appreciate them, we must conserve them as 'geoheritage' sites, not in museums or as artefacts, but as an integral part of today's landscape.
Geoheritage: significance, recognition & conservation Devayani Khare Nature Conservation Foundation (Oct 2021)
The talk covers a few examples of geoheritage in India, through the lens of biogeography, geology, and human history. The examples include the fossil-rich site of the Pranhita-Godavari basin, the laterite outcrops of Maharashtra and Goa, and the inselberg formations across India. The talk also explores questions like: can geoheritage sites be viewed at a landscape level? What insights can they offer for landscape conservation?
THE INDIAN CONTEXT: HERITAGE V/S GEOHERITAGE
Most people know of the UNESCO World Heritage List, where sites of cultural or natural significance have been inscribed and protected. In India, there are 40 sites listed at present, with several more on the tentative list.
Yet UNESCO has another classification for geological sites - Global GeoParks. There are 169 GeoParks in 44 countries at present, yet none in India.
A recent list published by the Geological Survey of India (GSI) lists 40 sites of geological importance, and an additional list of 26 sites as National Geological Monuments - some of which can be contenders for the UNESCO GeoParks tag. At present, few of these sites are protected or acknowledged, or bear interpretation signs. The nation is more keen on building (expensive!) statues celebrating Independence history of a few decades, when we could be preserving the narratives of millennia instead.
* Note: the revised list of 40 + 26 sites is not openly available, it was referred to in a Current Science article in July 2021, and is based on a conference status paper. The outdated list is available here, and a map with broad classifications of the geological sites can be accessed here.
Karst formations are created by the dissolution of rocks like limestone, dolomite or gypsum by subterranean drainage systems. These underground rivers create a network of stalactites and stalagmites, caves or sinkholes - depressions that form suddenly and can swallow up cars/buildings.
* Fun fact: Remember the rabbit hole that leads Alice to Wonderland? Seems it was inspired by a sinkhole! Can't guarantee we'd have similar adventures of we went down one of them though! Karst landscapes are often dramatic, with numerous distinct features: disappearing rivers, reappearing springs, runnels (small gutters) foibes (inverted funnel shaped sinkholes), abimes (steep vertical shafts) and may sometimes result in towers (eg. Lunan Stone Forest, China) or eggbox-like formations. Even staggering cliffs and caves, if the limestone occurs near the coast - like at the Diu coastline near Gujarat. In karst caves, the variety of features is often referred to as speleothems. The same root speleo can be found in speleology - the study and science of caves and karst landscapes, and spelunking - the practice or hobby of cave exploring. (The word spelunking could almost be the wet, rhythmic drip one hears so often in these subterranean caves!) The reason I've covered karst landscapes is because they are found in many parts of the country - chances are, there's one close to you! While the formation of most karstscapes is similar, each have unique speleothems that can help measure climate and environmental change over millennia, and host an incredible endemic or rare biodiversity.
Mawsmai cave, Meghalaya: Meghalaya has some of India's longest karst systems, with over 1,300 caves in the Khasi hills. The Mawsmai cave, located 3 kilometres to the south of Sohra/Cherrapunji, is the most-visited, and well-illuminated of the caves in the areas, created by percolating rainwater. What's incredible about Mawsmai, is that it is located within a sacred grove and is thereby, protected by the local community - a great example of how community championing of landscapes can be key to long-term conservation. Kailash cave, Chhattisgarh: located in the Bastar district, the Kailash cave is among other limestone caves in the thickly forested area, known for its staggering speleothems. The discovery of Mesolithic (~7000 years old, dated via Uranium/Thorium method) tools indicates that these caves were in use for millennia. Recent research in the nearby Kutumsar cave, lead to the discovery of rich, unique biodiversity - indicating that these caves could have good ecological potential. Borra Guhalu, Andhra Pradesh: located in Ananthagiri hills in Vishakhapatnam district, Borra Guhalu is another fine example of karstification. Rich in speleothems like stalactites, stalagmites, pillars, and flowstones (curtain-like formations), these caves bear evidence of micro-organisms that might have helped shape these subterranean features. Middle Paleolithic (~30-50,000 years ago) implements also indicate the age of the caves and provides archaeological evidence of early humans.
Naida caves , Diu. Credits: Dr.kpsingh111 via Wikimedia Commons
Diu seacliffs, Daman & Diu: geologically, the Diu island is comprised of shell limestones, formed by prehistoric marine creatures that inhabited the shallow waters. The shell limestone occurs in the form of parabolic dunes, ridges, or sheets that dip towards the sea, and can be seen at Dwarka, Okha, Mangrol, Veraval, Porbandar, and Diu. This is India's finest example of cliff formations in limestone, with features like tidal notches (indentations that mark tide levels), shore platforms (elevated structures), surf benches, as well as vugs or rock cavities lined with minerals, sinkholes, and solution channels - an elongated, water-carved channel. As the limestone was carved since the time of the Portuguese, several abandoned quarries serve as exposures for the geo-enthusiasts!
Here's a list of other limestone landscapes:
Baratang island, Andaman & Nicobar islands - more coastal limestone features!
Krem Puri, Meghalaya - vying for position as India's longest cave.
Belum caves, Andhra Pradesh - with Buddhist & Jain relics.
Patal Bhuvneshwar, Uttarakhand - interesting stories about the Pandavas & the Mahabharata abound.
Wadgaon Darya & Vambori Ghat, Maharashtra - for an alternate variety of limestone, known as tufa, with fossil leaf impressions.
Pachmarhi, Madhya Pradesh - more Bhasmasur & Shiva myths abound.