what caused explosion during cambrian period
Cambrian Period. The Cambrian Period is the first period of the Paleozoic Era spanning from approximately 540 to 500 million years ago. It was named in 1835 by the geologist Adam Sedqwick, after the region of Cambria in Southern Wales and England, where rocks of this age were first found. There were many small-scale, sporadic extinction events during the Cambrian Period. 2  A large-scale mass extinction event occurred approximately 500 million years ago. 3  Scientists believe was caused by a significant decrease in global temperature.