CLIMATE × EARTH

The Glaciation That Was Not a Snowball

~581 to 580 million years ago

Proterozoic · Neoproterozoic · Ediacaran

Ice reached middle and even low latitudes a third time, and stopped short. In Newfoundland, volcanic ash beds bracket the glacial debris between 580.9 and 579.9 million years ago, and one of the glacial units took at most 340,000 years to accumulate, far short of the millions of years the snowball hypothesis requires. Nor does a pale carbonate cap lie over it, as one does over the other two.

Why it matters

The first large Ediacaran fossils appear less than ten million years later, which has made this brief cold snap the favourite candidate for whatever set animals going, and, for the same reason, the best place to ask whether a cold snap sets anything going at all. A rival reading dissolves the moment into something far longer: the thirty or so Ediacaran glacial deposits known worldwide would not share a single age but record one continuous glaciation, running from 580 to 560 million years ago as one continent after another drifted into polar latitudes.

Dating & uncertaintyDisputed

Volcanic ash beds bracket the Newfoundland diamictite between 580.90 and 579.88 Ma, and one glacial unit accumulated in at most 340,000 years, far too short for a snowball. A competing reading gathers some thirty Ediacaran glacial deposits from around the world into a single ice age that moved with the continents from 580 to 560 Ma, in which case these dates fix the Newfoundland episode alone.

Sources

1. Pu et al. (2016), Geology · Dodging snowballs: geochronology of the Gaskiers glaciation and the first appearance of the Ediacaran biota
2. Fitzgerald et al. (2024), Precambrian Research · The Mall Bay Formation (Ediacaran) and the protracted onset of the Gaskiers glaciation in Newfoundland, Canada
3. Wang et al. (2023), National Science Review · A great late Ediacaran ice age

Earth history as one day

20:55:443 h 4 min before midnight

if Earth’s 4.54 billion years were compressed into a single day