Sagarmatha National Park

These mountains are young for mountains. Rivers cut deep valleys between them.

At least 25 peaks here are over 6,000 meters tall.

UNESCO calls the park one of the most geologically interesting regions in the world, with high, geologically young mountains and glaciers, and deeply cut valleys.

The park office says at least 25 peaks around the valleys rise over 6,000 meters, and seven besides Everest top 7,000 meters. High up, the valleys are shaped like a U. Lower down, below about 3,000 meters, the rivers have cut steep ravines through layered rocks and the granite beneath them.

UNESCO: the area represents a major stage of the Earth's evolutionary history, with high, geologically young mountains and glaciers and deeply incised valleys. The park office describes extremely rugged terrain ringed by 25 or more peaks over 6,000 m; seven (Baruntse, Lhotse, Nuptse, Pumo Ri, Guachung Kang, Cho Oyu and Nangpai Gosum) exceed 7,000 m.

The upper valleys are U-shaped, but below about 3,000 m the rivers cut steep ravines through sedimentary rocks and underlying granites; apart from some alluvial and colluvial deposits, the soils are skeletal.

Long glaciers sit at the top of each valley. Their meltwater feeds the rivers.

The glaciers are shrinking, and new lakes have formed.

The park's rivers are fed by long glaciers at the head of each valley, including the Khumbu, Ngozumpa, Imja and Nangpa glaciers. The Ngozumpa Glacier is 20 kilometers long, and the Gokyo lakes sit beside it. The Bhote Kosi, Dudh Kosi and Imja Khola rivers meet near the main village, Namche Bazar.

The park office says all its glaciers show signs of shrinking, and several glacial lakes have formed in recent decades. One, Imja Dzo, started to form in the 1970s.

The park office: rivers are fed by the long glaciers at each valley head (Nangpa on the Bhote Kosi, Ngozumpa on the Dudh Kosi, Khumbu on the Lobuje Khola, Imja under Everest); the 20-km Ngozumpa is bordered on the west by the four Gokyo lakes, held behind its lateral moraine (Ramsar site since 2007). The rivers meet near Namche Bazar and drain eventually into the Ganges.

All the glaciers show signs of retreat; Imja Dzo, which started to form in the 1970s, is given as 1,200 ha in area and 45 m deep. UNESCO notes the park monitors the impacts of climate change and is a major source of glacial fresh water for people downstream.

Snow leopards and red pandas live in the park.

Pine, fir and birch trees grow in the park.

UNESCO says the park is home to rare animals such as the snow leopard and the red panda. The park office also lists the musk deer among its main mammals.

The park climbs through several climate zones, from temperate zones up through sub-alpine and alpine land to a zone of snow and ice, and its main trees are pine, hemlock, fir, juniper and birch.

Main mammals (park office): snow leopard, musk deer and red panda; UNESCO adds that the park contains the world's highest ecologically characteristic flora and fauna.

Bioclimatic zones run from lower and upper temperate through sub-alpine and alpine to nival, and the climate from temperate to arctic; the major trees are pine, hemlock, fir, juniper and birch (park office).

Sherpa people live in villages in this park. They farm and trade.

Many visitors come to walk in the mountains.

UNESCO says Sherpa people have lived in this region for about four centuries, in more than 20 villages, mostly farming and trading. Their homes were left out of the park by law, and in 2002 a buffer zone was declared that includes the villages.

The park is a well-known place for mountain tourism. UNESCO reports 3,600 visitors in 1979 and more than 25,000 in 2010.

UNESCO: over 20 villages, with Sherpas who have inhabited the region for the last four centuries, mainly in agriculture and trade; their properties are excluded from the park by legal definition, and their traditional resource management has helped conservation. The buffer zone (275 km2, park office) was declared on 1 January 2002.

Tourism grew from 3,600 visitors in 1979 to over 25,000 in 2010 (UNESCO), boosting the local economy, health, education and infrastructure.

The air is thin up high. Climb slowly and rest.

Tell a grown-up if your head hurts.

The park's mountains are very high, and thin air can make people sick. The CDC says going up slowly gives the body time to adjust, and that children can get altitude sickness just like adults.

A headache is the main sign. The CDC says altitude sickness usually gets better in one to two days if people stop climbing higher.

CDC Yellow Book: avoid going from low altitude to a sleeping altitude of 2,750 m in one day; above 3,000 m, raise sleeping altitude by no more than 500 m a night; children are as susceptible as adults.

Headache is the cardinal symptom of acute mountain sickness, which generally resolves within 12-48 hours if travelers do not ascend farther.