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century of millions of years ago , Earth plunge into a deep - freeze that turned the major planet into a giant ball of water ice . Now , scientists have discovered sway marking this moment on a remote archipelago in the Inner Hebrides of Scotland .
The rock , dating to between 720 million and 662 million year ago , leave a rare complete record of the transition between a lovesome tropical surround and a " snowball Earth , " where glaciers encased the globe .
A Scottish rock outcropping called ‘the Bubble’ may provide clues to how Earth transitioned into the Cryogenian period.
If confirmed , the Garvellachs rocks could be declared a " golden spike " — a marker showing a passage to a fresh geologic age . Specifically , these stone would show the item when Earth moved from the Tonian period ( 1 billion to 720 million years ago ) to the Cryogenian menstruation ( 720 million to 635 million years ago ) .
" Most expanse of the world are missing this remarkable transition because the ancient glaciers scraped and eroded away the tilt underneath , but in Scotland by some miracle the transition can be see , " learn first authorElias Rugen , a researcher at University College London ’s Earth Sciences department , tell in a assertion .
scientist believe there were two snowball Earth events during the Cryogenian — the Sturtian glaciation and the Marinoan glaciation . The former issue was earlier and more life-threatening , lasting for around 57 million years , while the latter , more badly constrain issue , live between 15 and 20 million years .
An illustration of a “snowball earth”.
In a new study , published Thursday ( Aug. 15 ) in theJournal of the Geological Society of London , researchers take apart layers of rock 0.7 miles ( 1.1 kilometre ) thick , along with another 230 - animal foot - thick ( 70 meters ) level sitting beneath .
The researchers collected rock and roll sampling from two formations on the Garvellachs and analyzed tiny crystals called zircons . Zircons hold U , a radioactive element that slowly and steadily decays into lead , so the squad was capable to determine on the button when the rocks were work . The research worker set up that the lower section of rock music spring in tropical waters , when Earth was much warmer .
" These layers record a tropical marine environment with thrive cyanophyte lifetime that bit by bit became cooler , distinguish the ending of a billion year or so of a temperate mood on Earth , " Rugen said .
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The zirconium silicate geological dating showed the rocks were deposit between 720 million and 662 million year ago — a period that encompassed the conversion between the geological periods , from the temperate Tonian and into the Sturtian glaciation and Cryogenian period .
In July , illustration from the International Commission on Stratigraphy , which is part of the International Union of Geological Sciences , went to the Garvellachs to evaluate whether the site is a geologic marker . If it is ratify , the site will be marked with a favorable spindle .
" The layers of rock exposed on the Garvellachs are globally unequaled , " Rugen said .
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