Proterozoic

Well-identified events of this eon were the transition to an oxygenated atmosphere during the Paleoproterozoic; the evolution of eukaryotes via symbiogenesis; several global glaciations, which produced the 300 million years-long Huronian glaciation (during the Siderian and Rhyacian periods of the Paleoproterozoic) and the hypothesized Snowball Earth (during the Cryogenian period in the late Neoproterozoic); and the Ediacaran period (635-538.8 Ma), which was characterized by the evolution of abundant soft-bodied multicellular organisms such as sponges, algae, cnidarians, bilaterians and the sessile Ediacaran biota (some of which had evolved sexual reproduction) and provides the first obvious fossil evidence of life on Earth.

The outer zone has slightly undulated layers of Proterozoic deposits.

It is composed mostly of Archean and Proterozoic gneisses and greenstone which have undergone numerous deformations through tectonic activity.

Fennoscandia includes the Baltic Shield (also referred to as the Fennoscandian Shield) and has a diversified accretionary Archaean and early Proterozoic crust, while Sarmatia has an older Archaean crust.

Prior to 1550 Ma the craton comprised a number of active Proterozoic orogenic belts extending back in time to at least 2450 Ma.

During other times in its past, Laurentia has been part of larger continents and supercontinents and consists of many smaller terranes assembled on a network of early Proterozoic orogenic belts.

The mountain consists of foliated granite of Proterozoic age, with the foliation (layered structure of the rock) oriented almost vertically, creating natural weakness zones that have facilitated erosion processes.

The Ukrainian Shield and the Voronezh Massif consist of 3.2-3.8 Ga Archean crust in the southwest and east, and 2.3-2.1 Ga Early Proterozoic orogenic belts.