The Himalayas, in Pakistan, India, Nepal, and China, is the world's tallest mountain range. It was created when the tectonic plate that holds the Indian subcontinent ran into the Eurasian plate, which holds Europe and most of Asia. As the two plates pushed up against each other, the land was pushed up, forming the mountains.
Mt. Everest, the world's tallest mountain at 8,848 meters (29,029 ft) above sea level, is found in this range, along with nine other peaks over 8,000 meters (26,246 ft) in height, called the Eight Thousanders. The range outclasses every other mountain range in the world, and the tallest mountain outside Asia — Aconcagua, in the Andes — is only 6,962 meters (22,841 ft) tall. The Himalayan range also has the world's largest concentration of glaciers outside the polar regions.
Though the mountains in the Himalayas are the world's tallest, they are also among the youngest mountain ranges on the planet, with the substantial growth occurring in just the last million years. They 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 6.3 inches/year (16 cm/year).
When the Indian plate hit the Eurasian plate, parts of the former began to subduct (go beneath) the other, and its rate of movement slowed by about 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 mountains, 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 growing as quickly. Scientists think that this may be because the Eurasian Plate is starting to stretch out rather than just being uplifted. Still, this mountain range has the highest rate of uplift in the world, rising by about 5 mm per year. This rate of uplift, which calculates to about 3.1 miles (5 km) per million years, is not likely to be kept up for long.