The Park’s core area covers the upper headwaters of the Bhote Kosi, Dudh Kosi and Imja Khola rivers which fan out under the crest of the Himalaya Mountains on the Tibetan border and meet near the area’s main settlement, Namche Bazar. The buffer area reaches down the Dodh Kosi valley to Lukla 18 km south of Namche. The Park is enclosed by high mountain ranges and lies over extremely rugged terrain, deeply incised valleys and glaciers culminating in Sagarmatha / Mt.Everest, the world’s highest mountain. The catchments are ringed by 25 or more peaks over 6,000m, and seven - Baruntse, Lhotse, Nuptse, Pumo Ri, Guachung Kang, Cho-Oyu, and Nangpai Gosum - over 7,000m high. The rivers are fed by the long glaciers at the head of each valley: Nangpa Glacier on the Bhote Kosi, Ngozumpa Glacier on the Dodh Kosi, Khumbu Glacier on the Lobuje Khola and the Imja Glacier, one of eight which feed the Imja Khola under Sagarmatha. The Ngozumpa Glacier, 20 km long, is bordered on the west by the four Gokyo lakes impounded behind its lateral moraine. All the glaciers show signs of retreat and several glacial lakes have formed in recent decades; one, Imja Dzo which started to form in the 1970s, is now 1,200 ha in area and 45m deep. The upper valleys are U-shaped but below about 3,000m the rivers cut steep ravines through the sedimentary rocks and underlying granites. Near Namche Bazar they join the Dodh Kosi which drains eventually into the Ganges. Except for some alluvial and colluvial deposits at lower levels, the soils are skeletal.