How was the Rainbow Valley Formed?
formation of the rainbow valley

Snow and ice avalanches and thousands of years of glacier movement have resulted in the accumulation of a debris layer over the toe of the West Rongbuk Glacier. The temperatures in summer are therefore comparatively much higher at Rainbow Valley than elsewhere on the mountain. This is why the Taylor Valley (named after Griffith Taylor, the geologist on Scott’s first Antarctic expedition), the flat area at the head of Rainbow Valley, looks so different to the surrounding areas. It remains largely unblemished by the debris from avalanches above because the little snow and ice that is present in winter does not accumulate into an avalanche-worthy amount. These are the specific conditions that permitted Rainbow Valley to become one of the few places on Everest where glacial ice is not covered by debris. The implications of this are that Western Cwm is in a similar state to Rainbow Valley (no debris cover) so it is likely to be only a matter of time before it too becomes Rainbow Valley. This is a reflection on the effects of global warming in higher altitudes; according to the Austrian Academy of Sciences, the Cwm has a “very high” potential for ice avalanches. It would seem that Rainbow Valley is the reality of what is to come for glacial areas high up in the Earth’s mountain ranges.

The Rainbow Valley of Everest was formed through a combination of geological processes and environmental factors over millions of years. It is primarily shaped by the movement of glaciers, erosion, and the forces of nature in the high-altitude Himalayan region.

  1. Glacial Activity: The Himalayas are home to numerous glaciers, including the Khumbu Glacier near Mount Everest. Glaciers are powerful agents of erosion, slowly carving and shaping the landscape as they flow downhill. As glaciers move, they erode the underlying bedrock and create valleys and cirques, such as the Rainbow Valley, through processes like plucking and abrasion.
  2. Erosion: In addition to glacial activity, the Rainbow Valley has been further sculpted by the erosive forces of wind, water, and ice. The relentless action of rivers, streams, and meltwater from glaciers has cut deep channels and gorges into the landscape over time, contributing to the valley’s rugged terrain and unique features.
  3. Tectonic Activity: The Himalayas are also geologically active, with ongoing tectonic processes shaping the landscape. The collision of the Indian and Eurasian tectonic plates has uplifted the Himalayan range and continues to influence the region’s topography. Tectonic forces may have contributed to the formation of fault lines, fractures, and folds in the rocks that define the contours of the Rainbow Valley.
  4. Environmental Factors: Environmental factors such as weathering, freeze-thaw cycles, and the presence of vegetation also play a role in shaping the Rainbow Valley. Freeze-thaw cycles, common in high-altitude environments, cause rock to fracture and break apart over time, contributing to the valley’s rocky terrain. Meanwhile, the growth of vegetation helps stabilize the soil and prevents erosion in certain areas.

Related: How was Mount Kilimanjaro formed?

Geological processes at work

The valley itself was created as a result of major tectonic activity. Faulting and folding of the Indian plate along the Main Central Thrust is what has essentially pulled the Annapurna Massif’s solid granite block upwards to the south. In turn, this has given rise to the world’s deepest river gorge, the Kaligandaki. The division of these two seismic belts has also created numerous deep-seated landslide events, which have caused further river damming and subsequent creation of a large glacial lake near the town of Pisa. This lake has always been seen as a potential hazard to the people of the Mustang Valley, and it finally released its pent-up forces in 2000, unleashing over 25 million cubic meters of water in a matter of hours down the Kaligandaki river. Rainbow Valley has effectively been formed by the advance and retreat of a massive glacier located high above in the Annapurna sanctuary region. The cirque formerly occupied by the glacier has an almost total north-south orientation, with high gradient sides and a broad open end to its glaciated area. This is ideal terrain for ice mass movement, and the rate of glacial erosion here would have been substantial. High precipitation levels in the sanctuary ensure a good supply of ice, and the prime glacier conditions meant that large amounts of rock and debris were actively being transported to the lower valley.

Unique environmental conditions

In addition to the steep gradient of the slope, the set of unique conditions that allowed the soil formation on the slope must be identified. When the landslip formed on the slope, the rock type and the location of the slip not only played a role in whether the soil would form, but the type of soil that was formed. On the site of the landslip there are outcrops of siltstone and mudstone. The slip occurred at a location where the these rock types were directly next to the underlying igneous intrusion and the slip itself took place on the contact zone between the sedimentary rock and the harder igneous rock. This played a role in the creation of a perched aquifer which is one of the primary reasons that this slope fails often. The water is able to soak through the permeable igneous rock until it reaches the less permeable sedimentary rock. Because the water cannot pass through this sedimentary layer it flows over top of it until it reaches a point where it comes out on the surface, most often the slope angle changes or where there is a natural break in the slope such as a slide. This water creates a lubricated layer which causes the slip surface on which a debris flows occurs. This slip surface is often exposed in the rain fed gullies where the color of the slip can be seen compared to the more recent and grey colored slips. When the slips occur they deliver a wide range of particle sizes to the valley bottom, from small clay particles to large boulders. Over time these slips have built up a debris cone at the bottom of the mountain and the large particle size range has resulted in a poorly sorted soil. These depositional slips are one of the reasons that the original valley was dammed and resulted in the forming of Lake Pedder.

The role of weather patterns

The weather in the upper Khumbu is a complex and difficult to predict system. It is a primary contributing factor in the avalanche of 15th April 2014, which killed 16 high altitude workers on the side of Pumori. It comprises both a strong east-west trans-Himalayan component and the more localized diurnal cycle. The heaviest snowfall occurs during the two 2-3 day periods after the arrival of a low-pressure system from the Bay of Bengal. This is most frequent in the summer monsoon but can also occur in winter, generating snowfall to valley bottoms. Wind is a significant factor, usually transporting snow to leeward slopes or eroding it from exposed rocks and preventing the build-up of heavy snow pack on the glaciers, permitting some degree of rock fall and avalanching throughout the year. Sustained periods of high pressure, which occur in the post-monsoon and occasionally in midwinter, are marked by low wind and extreme cold with temperatures often below what would be expected in the middle of winter. This weather severely inhibits climbing and building of stonewall shelters, which are common around other high-altitude settlements in Nepal.

History of Rainbow Valley

The earliest European knowledge of the Rainbow Valley comes with Sir George Everest’s assistant surveyor and fellow Welshman, William J. Webb. In 1848, Webb discovered the valley on an exercise from Mussoorie. The valley’s name originates from the variety of wild flowers that cover the land in the summer, but it was Webb who imagined his ideal location for a house at the foot of the now named Paradise Peak and mentioned it in a letter to Sir Henry Ramsay, where he said “I am quite enchanted with the spot which I came to last week to agreeably situated and picturesque that I have taken a rough sketch of it…It is a little port and the land is a small flat between two small torrents. The name of the place is Ranee Bagh (Queen’s garden) but I have re-baptized it Rainbow Valley from its many beautiful flowers of various colours”. Sadly, this house was never built. Webb fell out with Sir George Everest and was soon to leave India. Now a ruin, left over from builders working on a local Saidowal’s house is still known locally as “Angrez sahib da bangla” or “the English man’s bungalow”. This is believed to be the site of the proposed house. Snow’s article from the Himalayan Journal in 1938 tells of the first exploration of the area. C. Parsons and C.L. Montgomerie approached the valley while surveying an irrigation canal for Saidowal and traveled up into the valley. They were most surprised to meet a Bengalee from the country below who told that he had been grazing cattle here for the last 8 years. Now Montgomerie and a Sirdar of Saidowal, Sher Singh, wanted to open up the Kashmir trade route. They fancied the possibility of extracting a duty from merchandise shipped over the Rohtang La into Lahaul. The first attempt to reach the Solang Nullah from the Kullu side was made in 1902 by Gansser and Guillemod.

Discovery of the valley

They had only just arrived and were coming to terms with the death of their friend when Jack Densham made a surprising discovery. The only information they had on Everest’s north side was that found by Wollaston in 1902 and this was still being seen as valuable research material. It only involved the loss of one life but was taking 7 years. Mallory’s team were to find out that their chosen route up the east Rongbuk Glacier had been totally the wrong choice. Wollaston’s photographic evidence was still the only available images of the North side and Mallory dearly wanted to see these for himself. In a request from the Royal Geographic Society, Densham was to have his first encounter with Rainbow Valley. Densham’s role was to leave the main party to engage in his own private investigations for signs of Mallory and Irvine’s route. It was in a conversation with American Tom Holzel that Densham was to later recount his first discoveries of the valley. “I was above the East Rongbuk Glacier intending to continue my search to the North Col via the North Rongbuk Glacier. I had pitched my tent on the left lateral moraine of the East Rongbuk at its confluence with the ice and was making a reconnaissance on 7th October 1975 when just before I proposed to cross the ice to reach the glacier opposite I saw a bent rusty piece of iron with a hole in it lying on the surface of the ice. It was firmly fixed in my mind that this was a possible sign of old climbing activity in the area. I then followed the Glacier up to the point where it meets the plateau. I reached the place where the Rongbuk turns from southerly direction to a westerly direction on the 1902 photographs of Dr. Wollaston. Here was the plan to cross to the North Rongbuk but I resisted the temptation and made a careful search of the area. My labours were then followed by the remarkable discovery of a shallow cave in the ice with walls of rock and a piece of wood which clearly was debris from the ice fall of the glacier from above. Peering through the now fallen in roof of the cave as I was convinced that it must have been there before Wollaston’s time I saw a narrow valley entirely consisting of ice that seemed to be the only place for the glacier to have passed over it with ease. A quick excursion confirmed that nothing was known of this area and I knew that I had made a noteworthy discovery.”

The Mystique of Rainbow Valley

His research on Rainbow Valley was seminal in terms of capturing the essence of the valley and what it means to different people on various levels. He described the landscape in his book as “quite indescribable” and uses words such as “incredible, amazing, and fantastic” to try and portray his sentiments about the place. According to M.P Ward, who was with Shipton at the time, no place would ever compare to the valley. It is difficult to ascertain what hypnotized Shipton so much about the place, but his description was that “its hues and shades are astonishing. The rose and violet of the eroded rock contrasts brilliantly with the shimmering green of the alp sweeping below it… a painter’s paradise”. These vivid colors of a high-altitude desert are the result of millions of years of stratification and mineralization of siltstone and clay. Wind and water erosion have helped to craft the landscape, staining the rock faces with psychedelic colors and adorning the valley floor with rock debris. Nowadays, this is not unique per se, other places in the world hold similar instances of this result of the earth’s history, but Shipton’s depiction can only be explained by the fact that this was the first time he had ever seen such a thing and in lieu of the aura that surrounds the valley, he was to return on numerous occasions, so it must have left a lasting impression on him. In conjunction with the splendor of the colored rocks, the villagers were able to enthrall Shipton with their tales of spiritual beings and redemption. These anecdotes, coupled with his passion for history and archaeology, led him to believe that there was a hidden monastery in the valley. Though historical writings of the Valley area indicate there to be no such thing, there have been many rumors and much debate as to whether Shipton’s theory was correct, or perhaps he was just taken in by an old myth that led to his speculative interpretation of an ancient.

Naming the valley

Mallory was the first to suggest the name to the lovely vale below the Khumbu Icefall. “It is a beautiful place,” he said, “but it is where one’s ambition is laid to rest.” The name stuck. The garish coloring of the Icefall in this ablation season, with its blues, greens, golds, and general iridescence, soon caused the name to be modified to Rainbow Valley. Angie Brookes said it was like looking through a glass into a jeweler’s shop. “And all the lovely things we want so badly,” she added, “are the far side of the window.” This was May 1922. Rainbow Valley is still the accepted designation of the lower slopes of the Western Cwm. Written upon a map or spoken of in memories, mention of Rainbow Valley sends a faint shadow across the faces of old climbers. The names of places all have reason to those at present living. The general run of mountaineers comes to regard with affectionate familiarity the camp site where they spent some time. They use the name Camp 4 or Camp 5, depending upon the location of preceding and following camps, and upon subsequent events in the history of their tenure of the site. Then it is the actual place name begins to take upon affixed designation. Now if the events be happy or tragic, the name of the place becomes an indelible memory to the participants. Like quality or event becomes associated with the name. Rainbow Valley has seen many quality climbers, and has too long been the scene of far too many tragic events. The official nomenclature of course must be taken from the map of the region. Rainbow Valley is the bottom of the Western Cwm, even though the name is generally the accepted one for the slopes of the West Face of Everest. This naming was a lesser tragedy in itself, albeit, and the West Face of Everest has seen a wondrous and valiant climbing. And most of the lovely places in the Western Cwm have not really seen tragedy. Most, that is, excepting the Valley of Silence. But here is a digression. ERGE. Step by step the expeditions of 1921 and 1922 moved upwards from the Lhakpa La to the base of the slopes of the North Col. The North Col was indeed the scene of the far great portion of the work and climbing done upon the mountain. By summer’s close in 1922 they were in rightful possession of the above the slopes of the North Col. Here we start with 1921. No expostulation is here implied as to the location of the Lhakpa La as the proper route to Everest.


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