Shrinking Panchachuli Glacier

Over the past few years I have been regularly visiting the Panchachuli Glacier in the Kumaon Himalaya. Accompanying me are a group of geology enthusiasts from all walks of life. This is an outreach effort I have undertaken in collaboration with Deep Dive India. 

Every time I make it a point to walk to the glacier snout where the river Dhauliganga emerges from an ice cave. Every time my experience of approaching the glacial terminus is different. The Panchachuli Glacier is a shape shifter. I have to walk a little longer each time to reach the snout, negotiating the changing configuration of rubble mounds and streams.

I thought I would document the retreat of the snout over time using field photos from my visits beginning year 2017 and supplemented by Google Earth imagery going back to the year 2000. I won't keep you in suspense. The glacier snout has retreated by about 1 kilometer in the last 25 years. That is by 40 meters per year. But the rate has varied, with an acceleration in the past 8 years.

Let's begin with a synoptic view of the glacial valley.

 

The walk begins at village Dantu. It is about 6 kilometers to the present position of the snout. The red lines are edges of old lateral moraines. They are stable features and are easily recognizable in the satellite images. They are my fixed marker posts against which I will track the changing position of the snout. Distance to the snout in all images is estimated from marker post A. 

Year 2000- Google Earth Imagery.

Notice the curvilinear cracks (white arrow) near the snout. The glacier retreats by slices of ices cleaving off these cracks. Between the two marker posts is a smaller glacial valley. Semicircular depressions and ponds have formed on the glacier surface due to thawing of the ice. The distance to the snout from A is about 1.3 kilometers.

Year 2012- Google Earth Imagery.

Distance to the snout from marker post A is 840 meters indicating a retreat of 460 meters in 12 years, averaging about 38 meters per year. The smaller valley still has a fair amount of ice accumulation.   

Year 2017- Field Photo.

This was taken during my first visit from a high vantage point along the trail to "Zero Point", a popular trekking spot along an old lateral moraine. 

Year 2017- Google Earth Imagery.

Between 2012 and 2017, the snout has retreated a further 120 meters, an average retreat of about 26 meters per year. The frontal part of the smaller side glacier is now showing signs of collapse. Pronounced curvilinear cracks have appeared and glacier retreat has left behind rubble mounds producing an uneven topography at the front.

Year 2023- Field Photo.

Taken from close to the 2017 vantage point. 

Year 2023- Google Earth Imagery.

The snout is now just 280 meters from marker post A. This implies a retreat of about 430 meters between the years 2017 to 2023. The average rate of retreat is an astonishing 71 meters per year. There are signs of significant changes around the glacial terminus. The snout is now up-valley of marker post B. The smaller valley between the marker posts is almost completely ice free. A surface drainage has developed along this side valley and joins the main Dauliganga stream just downstream of the snout. The multiple small streams in the area is due to drainage finding its way around fresh mounds of rubble.

My most recent visit was earlier this month in May. Google Earth does not have imagery from 2025. But I will share a field photo taken from the high slopes looking down towards the snout.

 

The snout has retreated by tens of meters and is almost in line with marker post A, strongly suggestive of high rates of retreat persisting over the last couple of years. The area around the terminus is a degraded landscape with rubble heaps everywhere. We could not get very close to the ice cave this time due to time constraints but I assessed it would have been a more difficult passage negotiating the multiple streams and boulders. 

The rates of retreat that I have estimated are a little higher than those made by geologists from other parts of the Himalaya. A Ministry of Earth Sciences press release from 2023 has shared some data on Himalaya glaciers. The average retreat rate for Ganga Basin glaciers is about 15 meters per year, while that for Brahmaputra Basin is about 20 meters per year. 

A more detailed study of Gangotri, India's most famous glacier, shows a retreat rate of 20 meters per year. Significantly, the retreat accelerated in the past few years to about 33 meters per year, a pattern I too have observed for the Panchachuli Glacier. 

Himalayan rivers provide water security for hundreds of millions of people in the Indian subcontinent. Glacial runoff contributes a timely and significant amount of water to these rivers. The Indian government is building and planning scores of dams in the Indus, Ganga, and Brahmaputra basins with elaborate arrangements of water use and water sharing with different stakeholders. Given the massive ice loss and changing climatic patterns, it is imperative that detailed feasibility studies of these projects in terms of both safety, and near, mid, and long term projections of water availability are carried out. 

I'm putting up this final image taken in May 2025 from near the Dhauliganga stream looking towards the terminus. 

 

It captures nicely the long term changes that have taken place. The blue line marks the top of the glacier. Fresh collapse has exposed shiny ice walls. The brown line above is the crest of an old lateral moraine, several hundred feet higher than the present day glacier surface. 

Is there a better landscape to contemplate and appreciate climate change and the dynamic glaciers which have shaped our planet over past centuries?

Deep Sea Mining, Early Indus Farmers, Indus Basin Dams

Some readings over the past couple of weeks- 

1) The Promise and Risks of Deep-Sea Mining: In late 1988 I visited the National Institute of Oceanography in Goa for a job interview. The buzz in the marine geology labs was about the discovery of manganese nodules on the deep sea bed of the Indian continental shelf. At that time, exploration had just started and the technology was not advanced enough to mine these lumps which contained, besides manganese, other metals like cobalt, nickel, and copper.  The nodule deposits were being looked at as a future resource. 

That day is upon us. Many countries have expressed an interest in mining the deep-sea bed for metals required for the transition away from fossil fuels. Metals concentration of Mn, Co, Ni, and Cu also occurs around hydrothermal vents. Not much is known about the ecology and biodiversity of these remote sites. Most experts feel that mining will result in extensive damage to the sea floor ecosystems and to life in the surrounding water column.

Daisy Chung, Ernest Scheyder, and Clare Trainor describe what is at stake in this beautifully illustrated article published by Reuters. 

2) Indus Valley farming started later than thought, radiocarbon study shows:  Mehrgarh, in Balochistan, Pakistan, was thought to be South Asia's oldest farming settlement going back to around 8000 B.C. New carbon dating of grains using a more robust dating method called Accelerator Mass Spectrometry has revised the date of earliest occupation to around 5200 B.C. Subhra Priyadarshini writes about the implications of this new date with regards to the origins and spread of farming in South Asia and cultural linkages of Mehrgarh to the Indus Civilization. 

3) Water Towers of the Indus Basin: Last month's heinous terrorist attack in Pahalgam, Jammu and Kashmir, India, has refocused attention on the Indus Water Treaty between India and Pakistan and the many hydropower projects that India is planning on the Indus and the Chenab rivers. These rivers provide water security to vast areas of India and Pakistan. 

Despite the importance of these rivers to local livelihoods, hydropower projects are being built without due  consideration being given to the impact dam construction and climate change will have on the Himalaya ecosystem..  

Parineeta Dandekar (story), Abhay Kanvinde (photos), and Michelle Hooper (story map) meticulously document the completed and planned hydropower projects along the Chenab river and point to the lapses in science and environmental governance that have taken place during the project planning process.

Oldest Himalaya Rocks

In Peninsular India, the most significant change in rock type occur across what is known as the Archean Proterozoic boundary.

Archean rocks, older than 2.5 billion years, are typically varieties of granite and granite gneiss. They formed when the earth was much hotter and silica rich continental crust was growing by injections of magma from the uppermost mantle and by partial melting of older mafic (silica poor) crust. At places the crust subsided by vertical movements, and lava and sediment filled the narrow depressions. These volcano-sedimentary rocks were deformed and metamorphosed to form linear schist enclaves within the granitic crust. The term granite greenstone terrain describes this rock association.

This phase of continental crust building petered out by around 2. 5 billion years ago. The thick crustal blocks or cratons became the nuclei for future continent growth. By 2 billion years ago or so in the Paleoproterozoic (the Proterozoic Eon spans from 2.5 billion years ago to 538 million years ago) , the Archean crust became the floor for several sedimentary basins. Erosion of the Archean rocks provided sediments that accumulated in these basins over the next 1 billion years, with long hiatuses punctuating pulses of sediment deposition. The names of these sites of deposition will be familiar to many readers and travelers.  Aravallis, Vindhyans, and Cuddapah, to name a few, represent this younger Proterozoic phase of crustal recycling. 

There was limited development in Peninsular India of younger sedimentary basins and as a result Archean and Proterozoic crustal sections are widely exposed all across the country.

The satellite imagery posted below shows one classic locality of the Archean Proterozoic boundary. This is from the Cuddapah Basin of South India.  

The Archean granitic terrain has a rough texture due to the bouldery nature of the landscape formed by weathering of fractured granite. Towards the east north east, the layering of sedimentary strata of the Cuddapah Basin is prominent and unmistakable.  The following graphic is a geologic log prepared to describe the succession of rock types from the Cuddapah Basin.

Source: Vivek S Kale and coworkers; Proc. Indian. Nat. Sci. Academy 2020.

Archean 'basement' and Proterozoic 'cover sequence' is a common stratigraphic motif of the Precambrian geology of India.

A few weeks ago I found an old paper from the 1970's on the sedimentology and stratigraphy of Tethyan sequences from the Kali valley area, near the Kumaon Nepal border. These are, as the name suggests, sediments deposited in the Tethyan Ocean along the  northern margin of the Indian continent. They range in age from the Proterozoic to the Mesozoic.

Here is the stratigraphic column from the paper. I have shown only the Precambrian (Archean and Proterozoic collectively make up the Precambrian) section of the column. The Central Crystallines are assigned an Archean age, while the Tethyan Sequence Martoli Formation is Early Precambrian. The name Proterozoic was not in use in the 1970's when this paper was written.

 Source: S. Kumar and coworkers; Journal of Paleontological Society of India 1977.

'Crystalline' in this context refers to the rock texture made up of large interlocking minerals formed during slow cooling of a magma or during high temperature metamorphism of a sedimentary rock.

The geologic sequence I described earlier took place along the northern margin of India too where the future Himalaya would form. At first glance the Himalaya sequence seems a replica of the geology of Precambrian Peninsular India. It records an Archean  'crystalline'  basement, succeeded by variably deformed and metamorphosed Precambrian (Proterozoic) sediments.

Except that it is wrong. There are no Archean age rocks exposed anywhere in the Himalaya. And the rock units immediately in contact with the Archean are not Early Precambrian.

When this paper was published there was precious little geochronology work done in the Himalaya. Geologists knew from sporadic absolute dating of Peninsular rocks that the granite and granite gneiss terrains are older than 2.5 billion years  (Archean).  The thick sedimentary sequences overlying the granite basement also were Precambrian as ascertained by dating intrusive granites and interbedded lava layers. The lack of any shelly fossils in them was another indicator of the Precambrian age of the cover sedimentary sequences. 

Given this familiarity with Peninsular geology, it would have been natural to assign the same chronology to a Himalaya rock sequence of high grade gneiss in contact with unfossiliferous sedimentary rocks. 

The Central Crystallines are now known as the Greater Himalaya Sequence and they are not Archean but Neoproterozoic (Late Precambrian) in age. Detailed work has shown that they represent sediments deposited roughly between 1 billion and 600 million years ago along the northern continental shelf of India. A paleogeographic reconstruction of the Himachal Himalaya by Alexander Webb and coworkers shows the original disposition of the different Himalaya rock divisions. Observe (A) that the Greater Himalaya (GHC) and the lower part of the Tethyan Himalaya (Haimanta/Martoli Formation) were deposited synchronously in adjacent areas of the continental shelf.  

 Source: Alexander Webb and coworkers; Geosphere 2011.

They look very different from each other today because they experienced different conditions during Himalaya mountain building. The Central Crystallines which began their life as marine sediments became crystalline gneisses and schists during high grade Cenozoic metamorphism 35 to 20 million years ago, while the Tethyan Sequence escaped being buried deep in the crust and retained much of their original sedimentary character. 

What about the oldest Himalaya rocks? These are Paleoproterozoic in age, dated to be about 1.9 to 1. 8 billion years old. The units Damtha, Berinag, Wangtu, Jeori and Baragaon in the Himachal Himalaya cross section are the Paleoproterozoic age rocks. They are remnants of a magmatic arc and associated basins which formed along the northern margin of India when continental blocks were colliding and suturing into an early supercontinent named Colombia.

Underneath these Paleoproterozoic rocks would have been the Archean 'basement'. But where is it now? 

We can take a step back and understand how the Himalaya are constructed. As the Indian continental crust collided and pressed into Asia, a crack or a fault initiated in the collision zone started propagating southwards, slowly splitting the Indian crust.  As India kept getting pushed under Asia along this master fault, slices of Indian crust get scraped off  and thrust upwards along subsidiary faults to form a growing mountain range. This tectonic evolution is depicted as stages B, C, D, E, F. You can also read my post Himalaya: A Critical Wedge for more details on the mechanisms of mountain building.

If as shown in the cross section, the faults that break and transport crustal sheets are located entirely within the Proterozoic and younger layers then the Archean rocks won't get incorporated into the Himalayan orogen. They lie below the basal detachment/master fault. Alternatively, this model may not be applicable everywhere in the Himalaya and there may be slivers of Archean rocks buried deep under the thrust pile, but erosion hasn't exposed them yet. 

In the geologic future, the plate tectonic engine that made the Himalaya will change track. The mountain ranges will stop growing. Erosion will wear down the Himalaya and eventually lay bare its roots. The Archean 'crystalline basement' so familiar all over Peninsular India will also be visible at the base of the gentle rolling hills that were once the mighty Himalaya.

Geology Infographics

I read a lot of technical literature on various geology topics. The papers are usually long and written in jargon filled language. It can be tough to hold your concentration and read through the paper in one sitting. What can help is a well complied figure which summarizes the ideas and the results of the study. By figure, I don't mean a graph or tabular display of data, but a graphic that presents the data with a combination of symbology, line art, text, and even images. Such infographics help in grasping the gist of the study and make reading the elaborate explanations easier (you still have to read them).

In this post I will showcase three infographics that I liked from my readings. I won't write long explanations about them, since the idea is to see if you can understand the broad findings by looking at a picture. Read the abstract of the paper to assess how effective the figure is.

1) Ediacaran Extinction and Cambrian Explosion.

The distribution through time and the changes in diversity of early complex multicellular life is depicted in this infographic. The evolutionary history of two distinct 'biotas' are tracked. The Ediacaran 'biota' is a catchall phrase that includes a diverse range of extinct large fossil organisms which may include some early animals as well. Metazoans ancestral to living animal groups are the second category. The carbon isotope curve shows two prominent deflections towards negative values, termed the 'Shuram' and "BACE" (Basal Cambrian Carbon Isotope Excursion) excursions. They are thought to indicate global environmental crises. Bookending this graphic are two diversity measures. On the left is the diversity of body fossils. On the right is the diversity of trace fossils, such as imprints, tracks, and burrows. 

Take home point. The Cambrian 'Explosion' is not about the origin of animals but their geologically rapid diversification whose roots lie a good 20 to 30 million years preceding the Cambrian events. Pulses of diversity expansion and collapse took place during that time period.

2) Dating Cave Art.

Humans have left some breathtaking artwork on the walls of caves all over the world. But how do we know when they were created? The pigments used in the drawings cannot be directly dated. One can use associated cultural artifacts to narrow down the time period. Or if lucky, mineral layers that entomb the artwork can be dated directly. This method still brackets the maximum and minimum age of the artwork. This infographic explains how artwork in a Spanish cave was dated using uranium and thorium isotopes. 

3) Angiosperm and Insect Coevolution.

I had written about this topic is detail in a previous post, but thought I'll share this infographic again. The Cretaceous was a time of great environmental shifts and changes in terrestrial biodiversity. Gymnosperms gave way to a dominance of angiosperms. The diversification of flowering plants had a large collateral impact on earth. The history of angiosperms and insect groups through the Cretaceous and Cenozoic is explained in this beautifully compiled infographic. 

If you have come across a science infographic that you particularly like, do share the link in the comments section.

Early Animals, Hominin Diets, Groundwater Governance

 A few links to interesting listening and reading.

1) Tracking the first animals on earth:  Unequivocal evidence of animals is preserved in soft sediments from about 570 million years ago. The fossil record of the Ediacaran to early Cambrian times (570 to 500 million years ago) has yielded rich information about the patterns of animal evolution. Apart from fossils, comparative genetic studies have given insights into how different animal groups are related to each other and the order of branching of these groups. Amazingly, organic molecules recovered from enigmatic fossilized taxa have been used to differentiate between animal and non-animal remains. Zoologist Matthew Cobb explains all this and much more about early animal evolution in about 30 minutes. Give it a listen! 

2) Plant-eating and meat-eating in Australopithecus: What did our ancient relatives eat? By ancient, I mean going back a million years or more. We can use isotopes of nitrogen to tease out information about diets. Carnivores have more nitrogen-15 enriched tissue than plant eaters. Carbon isotopes (C13 and C12) also yield information about the diet of herbivores. Grazers munching on grass take in more of the heavier isotope of carbon than browsers eating leaves and stems. Paleoanthropologist John Hawks discusses some recent work on nitrogen and carbon isotopes of Australopithecines and how the patterns of isotopic variation extracted from tooth enamel can be interpreted in terms of diets and life history. Fascinating stuff. 

3) Addressing Depletion in Alluvial Aquifers: Why Context Matters in Participatory Groundwater Management: India relies a lot on groundwater for agriculture. There are signs from many parts of the country of acute groundwater distress. Participatory Groundwater Management initiatives have had some success in addressing this distress. Pratik Kumar and Veena Srinivasan point out that these cooperative movements have been more successful in hard rock aquifers from different parts of the country than alluvial aquifers of northwest India. Geology matters. Aquifer properties matter. Hard rock aquifers are more sensitive to abstraction and are rapidly de-watered and recharged seasonally. Alluvial aquifers are spread over vast areas and water levels are less sensitive to abstraction. The amount you can extract doesn't vary with lowering of water level. 

People depending on hard rock aquifers experience the limitation of the resource yearly and are more willing to join cooperative initiatives to manage the resource.

I have just given a gist of the more elaborate arguments in the paper. The graphic below very neatly compares hard rock and alluvial aquifers. 

 Source: Pratik Kumar and Veena Srinivasan 2025

The paper is open access.