Himalayas
Ecology
- The flora and fauna of the Himalayas vary with climate, rainfall, altitude, and soils. The climate ranges from tropical at the base of the mountains to permanent ice and snow at the highest elevations. Owing to the mountains’ latitude near the Tropic of Cancer, the permanent snow line is among the highest in the world at typically around 5,500 metres (18,000 ft)[4]. In contrast, equatorial mountains in New Guinea, the Rwenzoris and Colombiahave a snow line some 900 metres (2,950 ft) lower[5]. The amount of yearly rainfall increases from west to east along the southern front of the range. This diversity of altitude, rainfall and soil conditions combined with the very high snow line supports a variety of distinct plant and animal communities. For example the extremes of high altitude (low atmospheric pressure) combined with extreme cold allow extremophile organisms to survive.[6]
- The unique floral and faunal wealth of the Himalayas is undergoing structural and compositional changes due to climate change. The increase in temperature may shift various species to higher elevations. The oak forest is being invaded by pine forests in the Garhwal Himalayan region. There are reports of early flowering and fruiting in some tree species, especially rhododendron, apple and Myrica esculenta. The highest known tree species in the Himalayas is Juniperus tibetica located at 4,900 metres (16,080 ft) in Southeastern Tibet.
Geology
- The Himalayas are among the youngest mountain ranges on the planet and consist mostly of uplifted sedimentary and metamorphic rock. According to the modern theory of plate tectonics, their formation is a result of a continental collision or orogeny along theconvergent boundary between the Indo-Australian Plate and the Eurasian Plate. This is referred to as a fold mountain.The collision began in the Upper Cretaceous period about 70 million years ago, when the north-moving Indo-Australian Plate, moving at about 15 cm per year, collided with theEurasian Plate. About 50 million years ago, this fast moving Indo-Australian plate had completely closed the Tethys Ocean, the existence of which has been determined bysedimentary rocks settled on the ocean floor, and the volcanoes that fringed its edges. Since these sediments were light, they crumpled into mountain ranges rather than sinking to the floor. The Indo-Australian plate continues to be driven horizontally below the Tibetan plateau, which forces the plateau to move upwards. The Arakan Yoma highlands inMyanmar and the Andaman and Nicobar Islands in the Bay of Bengal were also formed as a result of this collision.The Indo-Australian plate is still moving at 67 mm per year, and over the next 10 million years it will travel about 1,500 km into Asia. About 20 mm per year of the India-Asia convergence is absorbed by thrusting along the Himalaya southern front. This leads to the Himalayas rising by about 5 mm per year, making them geologically active. The movement of the Indian plate into the Asian plate also makes this region seismically active, leading toearthquakes from time to time.
