SnowballEarthPhasen

SnowballEarthPhasen is a framework used to describe the sequence of events proposed for the major Cryogenian glaciations, when Earth’s surface is thought to have been largely or completely ice-covered. The idea arises from the Snowball Earth hypothesis, which places these events in the Cryogenian period, roughly 720 to 635 million years ago. The phases are used to summarize how a planet could transition into, sustain, and emerge from near-global ice sheets.

A typical outline of SnowballEarthPhasen includes several stages. First, initiation, where climatic conditions and feedbacks—such as reduced greenhouse gases and changes in continental configuration—trigger the growth of glaciers beyond the polar regions. Second, expansion to near-global ice cover, with an ice-albedo feedback that promotes further cooling and stabilizes extensive ice. Third, maintenance of the frozen state for tens to millions of years, during which ocean circulation and chemistry are greatly altered. Fourth, deglaciation, driven by accumulating atmospheric CO2 from volcanic outgassing and reduced weathering, eventually tipping the balance toward warming. Fifth, postglacial recovery, marked by rapid climate warming and the deposition of cap carbonates and other new sediments as ecosystems reorganize.

Evidence for Snowball Earth includes glacial deposits found at tropical latitudes, cap carbonate sequences immediately above glacial rocks, and isotopic records indicating dramatic shifts in ocean chemistry. The exact timing, duration, and even the occurrence of a fully ice-covered planet remain subjects of ongoing research, with alternate models such as partially frozen "slushball" scenarios also considered.