The Himalayas are a vast mountain system in Asia, a geographical feature and a type of young fold mountain range, separating the plains of the Indian subcontinent from the Tibetan Plateau. The name itself is derived from the Sanskrit words hima ("snow") and ālaya ("abode" or "house"), meaning "abode of snow".
The mountain range began to form approximately 50 million years ago (Ma) when the Indian Plate collided with the Eurasian Plate. Before this, around 225 Ma, India was a large island separated from Asia by the Tethys Ocean. The northward drift of the Indian Plate, which began after the supercontinent Pangea broke up around 200 Ma, slowed significantly between 50-40 Ma, marking the initiation of the continental-continental collision and the uplift of the Himalayas.
The formation works through a process of orogeny, or mountain building, driven by plate tectonics. Because both continental plates have a similar rock density, neither could be subducted beneath the other. Instead, the immense compressional forces caused the crust to buckle, fold, and thicken to about twice the average thickness, forming the high peaks and the Tibetan Plateau. Sediments from the former Tethys Ocean were scraped off and accreted onto the Eurasian continent, forming the mountain range. The Himalayas are divided into parallel ranges, including the Outer Himalayas (Shiwalik), the Lesser Himalayas (Himachal), and the Great Himalayas (Himadri), which contains the world's highest peak, Mount Everest (8,848.86 meters).
The Himalayas connect to the broader concept of the Alpine orogeny and are a critical part of the Hindu Kush Himalaya region. They are often called the "Water Tower of Asia," as they are the source of major rivers like the Indus, Ganges, and Brahmaputra, supplying water to nearly 2 billion people.
The mountain range is still tectonically active and continues to rise at a rate of a few millimeters to over 1 cm per year due to the ongoing convergence of the Indian and Eurasian plates. However, the most significant recent changes are driven by climate warming, which is causing glaciers to melt and permafrost to thaw. This warming, which has been nearly twice the global average since the 1980s, is destabilizing mountain slopes and accelerating river migration rates, increasing the risk of catastrophic events like rock-ice avalanches and debris floods.