The geology of Uruguay combines areas of Precambrian-aged shield units with a region of volcanic rock erupted during the Cretaceous and copious sedimentary facies the oldest of which date from the Devonian. Big events that have shaped the geology of Uruguay include the Transamazonian orogeny (2000 million years ago (mya)), the breakup of Rodinia (700–500 mya) and the opening of the South Atlantic (~145 mya).