SchneeballErde

Schneeball Erde, a German term translating to "Snowball Earth," refers to a hypothesis that proposes the Earth may have been entirely or nearly entirely frozen over on multiple occasions in its history. These proposed glaciations, lasting for millions of years, would have covered the planet in thick ice sheets, from the poles to the equator.

The most prominent hypothesized Snowball Earth events occurred during the Neoproterozoic Era, specifically in the Sturtian (around 717-660 million years ago) and the Marinoan (around 650-635 million years ago) glaciations. Evidence for these periods includes geological formations such as glacial deposits found at latitudes that are now tropical, and the presence of "cap carbonates" – distinctive carbonate rock layers that often lie directly above glacial sediments, suggesting a rapid melting of ice and subsequent chemical precipitation.

The exact causes of Snowball Earth events are still debated but are thought to involve a complex interplay of factors. A significant role is attributed to runaway ice-albedo feedback. As ice sheets expanded, they reflected more solar radiation back into space, leading to further cooling and more ice formation. Variations in atmospheric carbon dioxide levels and the continental configuration are also considered crucial elements in initiating and eventually ending these extreme glacial periods. The eventual end of Snowball Earth phases is likely linked to a buildup of volcanic greenhouse gases in the atmosphere, which gradually warmed the planet and melted the ice.