Cambrian Explosion: from volcanos? (Introduction)

by David Turell , Monday, January 20, 2014, 15:18 (3749 days ago)

"Last year, a study suggested that microbes helped form continents by encouraging volcanic activity (New Scientist, 23 November 2013, p 10). Now Ryan McKenzie of the University of Texas at Austin and colleagues have shown that, in turn, volcanism may have shaped life during the crucial Cambrian period (see illustration).-Before the Cambrian, over 600 million years ago, Earth was virtually covered in ice. The first animals arose on this "Snowball Earth", but these "Ediacarans" did not look like modern animals.-Then came the Cambrian explosion. "You had single cell organisms, single cell, single cell, then weird Ediacaran oddballs, and ... suddenly ... snails and bivalves and sea stars and a whole range of groups that typify the record for the rest of time," says McKenzie's colleague Paul Myrow of Colorado College in Colorado Springs.-The animals that appeared during the Cambrian explosion gave rise to all the major groups alive today, from worms to starfish. But each group only contained a few species, and got no further. The next period is known as the Dead Interval, and was marked by mass extinctions. It was another 50 million years before animal life blossomed once more, during the Ordovician.-We already knew that Earth's temperature changed dramatically over these periods. It thawed in the early Cambrian then became stiflingly hot during the Dead Interval, before cooling again. "These are huge climate swings, from Snowball Earth to one of the warmest intervals of Earth history in the Cambrian," says Lee Kump of Penn State University in University Park."-
http://www.newscientist.com/article/mg22129522.600