The geological structure of India is divided on the basis of kalpas. The Kudappa and Vindhya systems formed during the Precambrian era span the eastern and southern states. During a short period of this kalpa, the geological structure of western and central India was also fixed. During the Cambrian, Ordovician Silurian, and Devonian ages of the Paleozoic era, Kashmir and Himachal Pradesh were formed in the western Himalayan region. The structures of the Mesozoic Deccan Trap can be seen throughout much of the northern Deccan. It is believed that the region was formed due to volcanic eruptions. The Carboniferous system, the Permian system and the Triassic system can be seen in the Western Himalayas. The construction during the Jurassic Saka can be seen in the Western Himalayas and Rajasthan. Manipur Nagaland, Arunachal Pradesh and the Himalayan Plateau were fairly new structures built during the Tertiary era. We can see the Cretaceous system in the Vindhya mountain range and Ganga Doab of central India. We can see the Gondwana system in the Vindhya and Satpura regions of the Narmada River. We can see the Eocene system in the Western Himalayas and Assam. We can see Oligocene formations in Kutch and Assam. The Pleistocene system was formed by volcanoes during this era. The Himalayan mountain range is formed by the spread and contraction of the Indo-Australian and Eurasian plates. The height of the Himalayas is 1 cm per year due to the continuous spread in these plates.