Himalaya - the bigger picture
|Triassic period||248-206 mya|
|Jurassic period||206-144 mya|
|Lower Jurassic epoch||206-180 mya|
|Middle Jurassic epoch||180-159 mya|
|Upper Jurassic epoch||159-144 mya|
|Cretaceous period||144-65 mya|
|Early (Lower) Cretaceous epoch||144-99 mya|
|Late (Upper) Cretaceous epoch||99-65 mya|
|Tertiary period||65-1.8 mya|
|Palaeocene epoch||65-55 mya|
|Eocene epoch||55-34 mya|
|Oligocene epoch||34-24 mya|
|Miocene epoch||24-5 mya|
|Pliocene epoch||5-1.8 mya|
|Quaternary period||1.8 mya to present|
|Pleistocene epoch||2 mya - to 10,000 years bp|
|Holocene epoch||10,000 years bp to present|
Source: Geological Society of America (1999).
The Himalaya can be divided into the main Great Himalaya range, the Cis-Himalaya lying to the south, and the Trans-Himalaya to the north. Within the Great Himalaya subsidiary ranges can be recognised, from west to east: Kashmir Himalaya, Northwest Himalaya, Kumaon Himalaya, Nepal Himalaya, and Assam Himalaya (running through Sikkim, Bhutan and Arunachal Pradesh). The Cis-Himalaya includes the Siwaliks and Lesser Himalaya, and the Trans-Himalaya comprise the Zanskar Ranges, Ladakh Range, and the Karakorum (with K2 peak, 8610 m).
The western extension of the Himalaya is the Baluchistan Arc that runs southwest from Kashmir through Baluchistan to the Arabian Sea. It continues through Makran as a low range of hills to finally join up with the Zagros Range in Iran.
The Indian (Deccan) plate was once situated far south of the equator, joined to SE Africa and Madagascar, forming part of the supercontinent Gondwana. It was one of the first plates to separate, beginning during the Early Cretaceous some 165 mya. The Indian plate finally rifted away from Madagascar 98 mya and started its rapid 6000 km journey northwards across the Tethys Sea towards Asia. During the late Cretaceous (80-65 mya), the Indian plate was moving at more than 15 cm per year, much faster than any modern plate movement, before colliding with Asia (Eurasian plate) about 45 mya.
The formation of the Himalaya was not a single event, as there have been several major mountain-building episodes and the process continues today. After the Indian plate collided, the Australian plate was released from Antarctica and itself began to move northward towards SE Asia. During the Eocene (around 45 mya), 5-10 my after the initial India-Eurasia collision, the Australian plate reached the Indian Plate and fused with it. The increased the forces exerted by the now much larger plate had a profound effect on the Himalaya, causing an intense phase of mountain building and uplift. Although the northward drift of India has slowed dramatically, the two continents continue to converge. Currently the Australian-Indian plate migration is estimated as moving northeast at 20-27 mm per year, causing the Himalaya to rise by about 3-5 mm (some say more that 1 cm) each year.