Recent studies may have again complicated the idea of a snowball earth.

Changes in ocean circulation patterns may then have provided the trigger of snowball Earth.

Fortunately, whatever conditions that created a snowball Earth millions of years ago don't seem to currently apply.

These ice ages were so severe they are sometimes called Snowball Earth.

Snowball Earth may inadvertently have accelerated evolution by reducing competition.

Snowball Earth was ended by incredibly violent climate change.

These so-called 'Snowball Earth' events are the subject of much scientific controversy.

There have been difficulties in recreating a snowball Earth with global climate models.

It may have triggered a snowball earth event.

Most scientists today believe that a "hard" Snowball Earth, one completely covered by ice, is probably impossible.

These two snowball earth events were previously considered together as the Varangian glaciation.

Several hypotheses exist for the initiation of the Snowball Earths.

There is a hypothesis that around 650 million years ago, the entire planet was frozen, called Snowball Earth.

This could cause conditions similar to Snowball Earth so cold could last millions of years.

According to the 'snowball Earth' theory, ice covered the entire Earth at this time.

A snowball Earth has profound implications in the history of life on Earth.

Beginning of a possible Snowball Earth ice age.

The glaciation may have covered the entire planet, in an event called the Snowball Earth.

Dr. Hoffman said the rise of animals might have prevented the snowball earth from recurring.

This is part of the Snowball Earth hypothesis.

The Proterozoic saw a couple of severe ice ages called snowball Earths.

The latter may have been a full-blown, and possibly the longest ever, snowball Earth episode, lasting 300-400 million years.

Ocean planet - the opposite concept of Snowball Earth.

The argument against the hypothesis is evidence of fluctuation in ice cover and melting during "snowball Earth" deposits.

When CO level dropped, the period known as Snowball Earth began.