subject: Continents Collision Marks The Beginning Of Our Planet [print this page] The period of continental collision was one of the Earths momentous times. It is a phenomenon of the plate tectonics of Earth that occurs at convergent boundaries. Continental collision is a variation on the fundamental process of subduction, whereby the subduction zone is destroyed, mountains produced, and two continents sutured together. Continental collision is known only from this planet and is an interesting example of how our different crusts, oceanic and continental, behave during subduction. Continental collision is not an instantaneous event, but may take several tens of millions of years before the faulting and folding caused by collision stop. Collision between India and Asia has been going on for about 50 million years already and shows no signs of abating. Collision between East and West Gondwana to form the East African Orogen took about 100 million years from beginning (610 Ma) to end (510 Ma). Collision between Gondwana and Laurasia to form Pangea occurred in a relatively brief interval, about 50 million years long. The collision marked the beginning of our planet.Twenty million years ago, North and South America were arranged in nearly the same positions as they are today. The big difference being, they were separated by a deep open channel called the Central American Seaway. There was no Panama and no need for a Panama Canal because there was clear sailing from the Atlantic to the Pacific.But the Earth is a geologically active planet with shifting crustal plates. During the time period between twenty and three million years ago, the Pacific Plate collided with the Caribbean Plate, pushing magma to the surface to make islands in the sea, and eventually creating a land bridge between the two continents. The movement not only changed the land, it disrupted ocean currents, opened a door to species migrations and probably altered the worlds climate.When the land bridge closed, equatorial waters could no longer mix. The Atlantic became saltier and the Pacific more dilute, creating a gradient that moves water in a giant loop around the globe today. Warm Atlantic water that used to pass through the gap moved northward, becoming the Gulf Stream. Scientists believe these changes created a warmer Europe and contributed to our recent cyclic ice ages.The land bridge also opened the way for species to cross from one continent to the other. Deer, horses, raccoons, bears and the camel ancestors of llamas moved south across the bridge. Anteaters, porcupines, opossums and armadillos moved north.Unfortunately, many large South America species couldnt compete with the North American animals and became extinct, changing the ecology of an entire continent. Mineral ore then accumulated deep under the rock. To mining those ores, we need mining equipment such as jaw crusher. As the professional manufacturer of complete sets of mining machinery, such as ball mill,vibrating screen,sand maker, Henan Hongxing is always doing the best in products and service. impact crusher:http://www.hx-crusher.com/impact_crusher.html Ball mill:http://www.hxjqchina.com/product-list_34.html dryer machine:http://www.hx-crusher.com/dryer_machine.html
