The appeal of the snowball hypothesis (Kirschvink, 1992) is that it provides credible explanations for many previously enigmatic features of Neoproterozoic Earth history. It explains:

1. the widespread distribution of LNGD on virtually every continent;
2. the paleomagnetic evidence that glacial ice lines reached sea level close to the equator for long periods;
3. the stratigraphic evidence that glacial events began and ended abruptly;
4. the reappearance of iron formations, exclusively within glacial units, after an absence of 1.2 billion years;
5. the world-wide occurrence of cap carbonates with unusual features, resting sharply above successive LNGD;
6. the existence of very large positive and negative δ¹³C anomalies, before and after each glacial event respectively.

The alternative "loophole" model (Hyde et al., 2000; Runnegar, 2000) compromises many of these explanations (Schrag and Hoffman, 2001), and is therefore less attractive. As the observations have no parallel in the Phanerozoic, it should not be surprising that the events responsible for them have no Phanerozoic counterparts.

Following Kirschvink (1992), we speculate that a preponderance of continents in middle to low latitudes created conditions favorable for snowball events. Such conditions would be rarely met in Earth history overall, but could persist for intervals long enough to engender repeated snowball events, as is observed. A possible trigger for individual snowball events, suggested by carbon isotopic data in many areas (Halverson et al., 2002), arises counter-intuitively from a dependence on greenhouse methane, engendered by the same unusual continental distribution (Schrag et al., 2002).