104 - Columnar basalt

Hello friends, Welcome to the Rock Repository at the Department of Geology, Shivaji Science College, Nagpur. I am columnar basalt also called columnar jointing, i am a geological structure where sets of intersecting closely spaced fractures, referred to as joints, result in the formation of a regular array of polygonal prisms, or columns. These columns of me are most likely a volcanic rock called basalt. When I form long, straight columns, its called colonnade. When I have more irregular shapes that look like they’ve been pushed or morphed it’s called entablature. I have formed in many places around the world that have a lot of volcanic activity. They are well-known in certain places like Iceland, Ireland, and the United States. The late Cretaceous Deccan Traps of India constitute one of the largest volcanic provinces of Earth, and examples of columnar jointing can be found in St. Mary's Island in the state of Karnataka. Thank you for visiting.