Background

Heron's geological map of Everest region

The 1921 Everest reconnaissance expedition was funded by the Royal Geographical Society, the Alpine Club and the Survey of India with a remit to explore the approaches to Mount Everest from Sikkim and through Tibet, and to investigate possible routes for climbing the mountain. Reaching the summit was not a primary objective. For geographical survey work the Survey of India appointed its own officers and the Geological Survey of India appointed Heron to conduct a widespread geological survey and to produce a map. Charles Howard-Bury led the expedition. Harold Raeburn and Alexander Kellas were to lead the climbing team but, after Kellas' sudden death on the walk-in, and Raeburn's illness requiring him to return to base, George Mallory effectively became lead climber. Henry Morshead led the survey work.^[11]

Heron's travels

Heron in ceremonial attire

Heron's party left Darjeeling on 19 May 1921. To begin with Mallory had found Heron dull in conversation but in the course of the long trek across the Tibetan plateau he formed a much better opinion. In letters home to his wife Ruth he wrote that Heron was a "solid treasure", was "cheerful and good-natured", and that although he was good at dealing with the porters he was no climber.^[12] Later, while exploring north of Everest, Mallory's photographs with one camera were ruined because he had been putting in the photographic plates back to front. Writing home he blamed Heron for not instructing him properly.^[13]

Starting from the expedition's base at Tingri on 25 June, Heron set off south west towards the Kyetrak Glacier with Oliver Wheeler. Howard-Bury joined them later and while Wheeler surveyed on his own, they explored the area of the Nangpa La where Heron discovered marine fossils in the limestone at heights never thought possible.^{[14][15][note 1]} By 4 July they had moved to see Mallory and Guy Bullock in the Rongbuk valley and then they headed on north and then east to find a suitable base from which to explore the eastern approaches to Everest. They decided the Kharta valley was suitable.^[17][18] Heron separately surveyed from Kharta back to Tingri and went on to make several geological expeditions to the north. He returned to Kharta on 19 August after exploring, in very bad weather, a broad east-west region as far north as the Yarlung Tsangpo River.^[19][20] Heron visited the main party at Kharta on 14 September and then set off to explore Everest's eastern valleys taking no part in reaching the Lhakpa La and, beyond, the North Col.^[21]

For Heron the expedition ended on 20 October when the group he was with arrived back in Darjeeling.^[22] Largely working alone, he had made geological investigations over 8,000 square miles (21,000 km²) and had produced the promised geological map.^[23][24] He also wrote the geological chapter for Howard-Bury's book about the expedition.^[25][26]

Geological results

Heron based his map on the topographical map that was being drawn by Morshead and his team, although for much of the time the region he was in had not yet been mapped so he had to transcribe his observations later.^[27] The scale was four miles to an inch (1:250,000). Heron discovered that the Tibetan plateau was intensely folded sedimentary Jurassic shale and Cretaceous limestone with an east-west strike with, he considered, the folding indicating movement from the north. The uppermost limestone, Cretaceous and later, contained fossils but the shale had little by way of fossils. Nearer to the mountains the shale was underlain by limestone (possibly Triassic or Jurassic) metamorphosed into crystalline form and into calcareous gneiss. In the vicinity of the high mountains the rock was biotite gneiss. The high peaks north west of Everest had granite intrusions and possibly the same would apply on Everest itself. He considered that the biotite gneiss was probably an igneous intrusion into the calcareous gneiss. There were no ores or minerals of commercial interest.^[26]

The region surveyed was in Tibet from the Tsangpo in the north down to the Nepalese border. It included the basin of the Arun River, the region north and east of Everest, and in the west the headwaters of the Bhote Koshi flowing into Nepal.^[26] Heron considered that a river had once flowed east–west just north of Himalaya, possibly joining the Tsangpo as a tributary. The Arun River flows southwards between Everest and Kangchenjunga and he thought that its headwaters had cut backwards and to the north until the east–west river had been captured in the middle of its course. The Arun Gorge is 5,000 feet (1,500 m) deep as it cuts completely through the Himalayan ridge and for the origin of its upper part Heron was "unable to give an explanation".^{[28][note 2]}

Complaint from Lhasa

While the expedition was underway, on 28 September 1921, Charles Bell, who was in Sikkim as the British diplomatic representative to Tibet, received a telegram from the Tibetan prime minister passing on a complaint from the dzongpen of Shekar. The expedition had disturbed the monks at Rongbuk Monastery and, moreover, climbers had been digging up rubies, turquoises and other precious stones.^[31]

It was agreed that Mount Everest might be explored but if this is used as an excuse for digging earth and stones from the most sacred hills of Tibet, inhabited by fierce demons, the very guardians of the soil, fatal epidemics may break out amongst men and cattle. Kindly prevent officials wandering about and effect their early return.

Bell knew that no precious stones had been found but he was well attuned to Tibet culture and sympathetic with it so he understood the sensitivities. To make matters worse, a scarlet fever epidemic had indeed broken out in Tibet in late 1921.^[31]

Heron's explanation was not helpful:

I have to plead "Not Guilty" to the charge of being a Disturber of Demons. I did no mining and the gentle hammer tapping which I indulged in was, I am sure, insufficient to alarm the most timid of the fraternity. Perhaps it was Wheeler through his cairn-building propensity! However this time I shall exorcise them by the pious refrain of "kiki so so lha so lha" to a hammer accompaniment.

Bell was infuriated and no official geologist, and certainly not Heron, would ever take part in an Everest expedition again. Moreover, officers of the Survey of India were also to be excluded.^{[31][note 3]}