The Mesoarchean ( /ˌmiːzoʊ.ɑːrˈkiː.ən/, also spelled Mesoarchaean) is a geologic era within the Archean Eon, spanning 3,200 to 2,800 million years ago. The era is defined chronometrically and is not referenced to a specific level in a rock section on Earth. Fossils from Australia show that stromatolites have lived on Earth since the Mesoarchean. The Pongola glaciation occurred around 2,900 million years ago. The first supercontinent Vaalbara broke up during this era about 2,800 million years ago.