Underwater volcanoes ended Snowball Earth, a period of millions of years which blanketed our planet in a thick layer of ice. According to scientists, Snowball Earth spanned 720 million years ago to 640 million years ago.
This intensive ice age which engulfed the Earth entirely suddenly came to an end. Until recently, scientists couldn’t pinpoint the exact factors that turned the Earth from an iced, lifeless planet to one brimming with life and vegetation. The hypothesis around Snowball Earth maintains that when the Rodinia supercontinent broke in different tectonic plates, our planet froze over. The process was triggered by a large quantity of dissolved minerals washing away into the oceans.
It was the dissolved minerals which by altering the chemistry of the ocean led to the decline of carbon dioxide in the atmosphere. Carbon dioxide along with other atmospheric gases trap the heat and lead to a warming of the atmosphere.
Such gases are aptly called greenhouse gases. With carbon dioxide declining, the atmosphere cooled to the degree that triggered the Snowball Earth. Once our planet was covered in ice, the massive ice sheets contributed to the perpetuation of Snowball Earth for millions of years. The heat of the sun was reflected by the massive ice sheets blanketing Earth. Yet underneath the icy blanket of Snowball Earth, volcanic activity was already planting the seeds of change.
According to the study led by Thomas Gernon and published in the Nature Geoscience journal, underwater volcanoes ended Snowball Earth.
“When volcanic material is deposited in the oceans it undergoes very rapid and profound chemical alteration that impacts the biogeochemistry of the oceans”,
stated Thomas Gernon in a press release. In addition, the study found that geochemical as well as geological features linked to Snowball Earth may be pinpointed to underwater volcanism along the ridges of the mid-ocean.
During Snowball Earth, the frozen exterior was complemented by intense activity under the massive ice sheets. Shifting plate tectonics and volcanic activity released carbon dioxide which build up to such an extent that it was released back into the atmosphere at a constant pace. This led to the warming of the atmosphere was once more.
Underwater volcanoes led to the production of cap carbonates. Cap carbonates have been associated with the transition from the frozen Snowball Earth to the life-brimming Earth. Fully reliant on highly alkaline seawater, cap carbonates were produced as underwater volcanoes erupted in shallow waters. With the deposits of lava ending up on the seafloor, the hyaloclastite rocks reacted with the icy ocean to release phosphorus, magnesium, silica and calcium. Underwater volcanoes were sufficient to sustain the production of cap carbonates.
Moreover, as this latter phase resulted in the release of phosphorus in the ocean and atmosphere, this is believed to have been the key element for the global reset. Underwater volcanoes ended Snowball Earth as the slow process developed over millions of years.
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