{"id":482226,"date":"2026-05-13T08:03:12","date_gmt":"2026-05-13T08:03:12","guid":{"rendered":"https:\/\/www.europesays.com\/ie\/482226\/"},"modified":"2026-05-13T08:03:12","modified_gmt":"2026-05-13T08:03:12","slug":"earths-longest-ice-age-may-have-repeatedly-thawed-and-refrozen-for-56-million-years","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/ie\/482226\/","title":{"rendered":"Earth\u2019s Longest Ice Age May Have Repeatedly Thawed and Refrozen for 56 Million Years"},"content":{"rendered":"

\"Moon<\/a>Artistic representation of a Snowball Earth. Credit: Wikimedia Commons.<\/p>\n

The Sturtian glaciation<\/a> was one of the most extreme climate events in Earth\u2019s history. Beginning around 717 million years ago, ice spread and covered most of the planet, even reaching the tropics and sealing much of the ocean beneath a frozen shell. This was Snowball Earth, or something very close to it.<\/p>\n

Even though it happened so long ago, geologists are quite certain that this event took place. But there\u2019s a timing issue. It lasted roughly 56 million years, far longer than standard Snowball Earth models can easily explain. <\/p>\n

Now, a new study suggests the planet may not have stayed frozen the whole time. Instead, Earth may have repeatedly thawed and refrozen as fresh volcanic rock drew carbon dioxide<\/a> from the air, creating a climate loop that helped explain both the ice age\u2019s extreme length and the survival of oxygen-using life.<\/p>\n

Ancient Climate Cycle<\/p>\n

The Sturtian glaciation was a deep ice age that gripped Earth from about 717 million to 660 million years ago, during a period called the Cryogenian period<\/a>. It came long before dinosaurs<\/a>, forests, or vertebrates. It was followed later by another major freeze, the Marinoan glaciation<\/a>.<\/p>\n

Geologists know the Sturtian was severe because ancient rocks preserve signs of glaciers spreading across continents. Some deposits suggest ice reached low latitudes, perhaps even the tropics. But the rock record also includes hints of open water and more varied conditions during the same broad interval.<\/p>\n

That mix has always been awkward. <\/p>\n

A fully frozen Earth is hard to keep frozen for tens of millions of years because of volcanoes. Volcano eruptions<\/a> releasecarbon dioxide. But when the planet is covered in ice, the normal process that removes CO\u2082 from the air (especially rock weathering) slows dramatically. So CO\u2082 should build up in the atmosphere, strengthen the greenhouse effect<\/a>, and eventually melt the ice.<\/p>\n

A slushier Earth, with patches of open ocean, is also hard to maintain because it gives the planet more ways to warm up. Dark open water absorbs much more sunlight than bright ice. More open water can also support more exchange between the ocean and atmosphere. So once patches of ocean appear, they can help the planet absorb heat and move further away from a deep freeze.<\/p>\n

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So the awkward part is this: a hard Snowball should thaw too soon because CO\u2082 builds up, while a slushy Snowball should be even less stable because open water helps absorb heat. Yet the Sturtian lasted<\/a> around 56 million years.<\/p>\n

Charlotte Minsky, a graduate student at the Harvard John A. Paulson School of Engineering and Applied Sciences, may have figured out why this worked. Along with her colleagues Robin Wordsworth, David T. Johnston, and Andrew H. Knoll, Minsky tested a different possibility. They linked ancient climate to the carbon cycle\u2014the movement of carbon through air, rocks, oceans, and living things.<\/p>\n

Basically, their model says the climate continuously warmed up and froze again for over 50 million years.<\/p>\n

The Feedback Loop<\/p>\n

The Harvard team points to a vast volcanic region<\/a> in what is now northern Canada: the Franklin Large Igneous Province. It erupted shortly before the Sturtian began and spread huge amounts of basalt<\/a> across the surface.<\/p>\n

Basalt matters because it reacts strongly with air and water. As it weathers, it removes carbon dioxide from the atmosphere and locks carbon away in minerals and ocean sediments. Less CO\u2082 means a colder planet.<\/p>\n

The team\u2019s model suggests that fresh Franklin basalt could have drawn down enough CO\u2082 to help push Earth into Snowball conditions.<\/p>\n

Then the loop began.<\/p>\n

When ice covered much of the planet, weathering slowed down. Rain and air could no longer reach large areas of exposed rock. At the same time, volcanoes kept releasing CO\u2082 into the atmosphere. With less weathering to remove it, the gas built up. Eventually, the greenhouse effect strengthened enough to melt back the ice.<\/p>\n

That thaw exposed more fresh basalt. Weathering restarted. CO\u2082 dropped again. Earth cooled again. Ice returned.<\/p>\n

The planet rinsed and repeated that for about 56 million years.<\/p>\n

How Did Life Find a Way?<\/p>\n

The freeze-thaw idea also helps with another puzzle: oxygen.<\/p>\n

At the time, Earth was still a world of microbes. There were no animals, plants, forests, or fish, and complex life was only beginning to take shape in the oceans. Most organisms were single-celled, but many still needed oxygen. So when the Sturtian freeze hit, much of this tiny life had a problem, not just because of the temperature, but because of the oxygen.<\/p>\n

A continuous global freeze could have strained the systems that kept oxygen in the air and oceans. But under the new model, those organisms didn\u2019t have to endure one continuous 56-million-year freeze. Instead, they may have survived a chain of harsh but temporary freezes, broken up by warmer windows.<\/p>\n

\u201cThis could help explain how aerobic life persisted through such an extreme interval,\u201d Minsky said in a statement<\/a>.<\/p>\n

The rock record also fits better with the stop-start freeze theory. Some Sturtian deposits <\/a>point to glaciers, while others suggest open water broke through at times. A climate that kept thawing and refreezing would make sense of those mixed signals.<\/p>\n

Not a Dead World<\/p>\n

\"\"<\/a>We need to talk about Enceladus. Credit: Wikimedia Commons<\/p>\n

The new model doesn\u2019t mean the Sturtian was a breeze to live in. It was still one of the most extreme events in our planet history. Life still had to survive some extreme conditions.<\/p>\n

But it gives the long ice age<\/a> a clearer structure. The same cycle could explain why the Sturtian lasted about 56 million years, why some rocks point to open water, and why oxygen-using life did not disappear.<\/p>\n

The idea also reaches beyond Earth. The authors suggest that similar cycles could happen on rocky exoplanets with volcanoes, exposed basalt, and a working carbon cycle. Such worlds might not stay frozen forever. They could move back and forth between ice and warmth.<\/p>\n

That puts the Snowball planets in a new perspective in the search for life. A frozen surface would not necessarily mean a dead world. It might mark one phase in a longer climate cycle.<\/p>\n

The study was published in the journal Proceedings of the National Academy of Sciences<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"Artistic representation of a Snowball Earth. Credit: Wikimedia Commons. The Sturtian glaciation was one of the most extreme…\n","protected":false},"author":2,"featured_media":482227,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[77],"tags":[86342,210893,210894,38454,442,159042,18,6123,210895,19,17,68987,133,155860,159047,30480],"class_list":{"0":"post-482226","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-ancient-earth","9":"tag-atmospheric-oxygen","10":"tag-basalt-weathering","11":"tag-carbon-cycle","12":"tag-climate-change","13":"tag-cryogenian","14":"tag-eire","15":"tag-exoplanets","16":"tag-franklin-large-igneous-province","17":"tag-ie","18":"tag-ireland","19":"tag-paleoclimate","20":"tag-science","21":"tag-snowball-earth","22":"tag-sturtian-glaciation","23":"tag-volcanoes"},"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@ie\/116566229862194472","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/482226","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/comments?post=482226"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/482226\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/482227"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=482226"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=482226"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=482226"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}