The Himalayas, in Pakistan, India, Nepal, and China, is the world's tallest mountain range. It contains Mt. Everest, the world's tallest mountain, which rises 8,848 meters (29,029 ft) above sea level, and nine other peaks over 8,000 meters (26,246 ft) in height, called the Eight Thousanders. The Himalayas outclass every other mountain range in the world -- the tallest mountain outside Asia, Aconcagua in the Andes, is only 6,962 meters (22,841 ft) tall. The Himalayan range is also the world's largest concentration of glaciers outside the polar regions.

Though the Himalayas are the world's tallest mountains, they are also among the youngest mountain ranges on the planet, with the substantial growth occurring in just the last million years. The Himalayas began growing about 50 million years ago when the Indian subcontinent, which used to be an island continent beneath Eurasia, slammed into the Eurasian continent due to continental drift. Prior to this, the Indian plate was one of the fastest-moving tectonic plates in the world, traveling northward at a rate of 16 cm/year (6.3 in/year).

When the Indian plate hit the Eurasian plate, parts of the former began to subduct (go beneath) the other. Its rate of movement slowed by about a half. The soft sediments that covered the northern edge of the island continent began to crumple, being uplifted, while the Indian Plate also pressed the Eurasian plate upwards. This is the birth of the Himalayas. They emerged in the former location of the Tethys Ocean, which had existed for 200 million years prior. Even today, fossils of coast-dwelling creatures can be found in the Himalayas, as the high peaks were once part of the Indian coastline.

Some of the greatest earthquakes in history have occurred due to tectonic forces released by the interaction between the Indian Plate and the Eurasian Plate. More recently, in the last few million years, the mountains have stopped uplifting as quickly. Scientists think that this may be because the Eurasian Plate is starting to stretch out rather than just being uplifted. Still, the Himalayas have the highest rate of uplift in the world, rising by about 5 mm per year. This rate of uplift, which calculates to about 5 km (3.1 mi) per million years, is not likely to be kept up for long.