Monday, April 17, 2023

3961 - ICE AGE - cycles of Earth's environment?

 

-   3961 -   ICE AGE  -  cycles of Earth's environment?     Our planet hasn’t always been the warm, inviting place we know today. At least five times in its history, Earth froze over, locked in the grip of an ice age. Scientists sometimes refer to these periods as “Snowball Earth.”


----------------------  3961  -   ICE AGE  -  cycles of Earth's environment?

-     Earth 650 million years ago during the “Marinoan glaciation”, the idea of Slushball Earth may change how we view that past ice age.  Not Snowball Earth, More of a Slushball Earth.

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-  Everything was covered with ice, making life difficult, if not impossible. But, there’s new evidence that during at least one of these icy periods, parts of Earth’s surface could have been more like a giant mushy ball of slush.

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-     Geologists are studying rock cores that contain material laid down on the ocean bottom during a period called the “Marinoan Ice Age”. It occurred some 635 million years ago during a geologic period called the “Cryogenian”.

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-    The Marinoan event was extreme. Over the course of 15 million years, it slathered much of the planet with ice.   We believed that Earth had frozen over entirely during this long ice age. But maybe it was more of a ‘Slushball Earth”.

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-    Recent evidence found in China is changing that “Snowball Earth” view. Scientists are analyzing those rock cores. They discovered that habitable open-ocean conditions were more extensive during that time than everyone assumed. This was true for oceans that lay between the tropics and the polar regions. These places provided safe havens for single-celled and multi-celled organisms during the waning stages of the Marinoan ice age.

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-    Rock cores from that time have traces of a tiny seaweed organism called “benthic phototropic macroalgae”. It was around back then and still exists today on the sea bottom. It’s also a basic part of most ecosystems where it exists, but it needs sunlight to convert water and carbon dioxide into energy through photosynthesis.

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-     The fact that it existed back on Slushball Earth tells us that it got the sunlight it needed. That suggests the oceans, or at least the shallower bodies of water, weren’t completely frozen over.

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-    While deep water likely did not contain oxygen to support life during this period, the shallow seas did.  The ice age probably had many periods of freezing and melting over the span of 15 million years.

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-   If that occurred, then it’s highly likely that life persisted, particularly in the shallow seas.  There may have existed potential open-water conditions in the low and middle latitudes several times.   These conditions in surface waters may have been more widespread and more sustainable than previously thought and may have allowed a rapid rebound of the biosphere after the Marinoan Snowball Earth.

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-    The existence of these macroalgae and other multicellular organisms might have played a role in both starting and ending that long-ago ice age. Another glaciation later in the Cryogenian likely covered much more of the planet.

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-   We don’t know for sure what triggered these ice ages, but suspicion is it was related to multicellular organisms that removed carbon from the atmosphere, leading to carbon burial and the cooling of the Earth.  Today, we’re releasing carbon quickly in huge amounts and it is having a big impact on global climate.

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-    That same warming by life forms probably contributed to the end of the Marinoan. Life flourishing in those shallow ocean regions released a lot of carbon dioxide, which warmed the atmosphere and contributed to glacial thaw.   We know that carbon dioxide is one of the most important greenhouse gases. So we see how changes in the carbon cycle have an impact on the global climate.

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-    There have been five major ice ages in Earth’s history. The “Huronian” occurred 2.4 to 2.1 billion years ago.

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-    The “Cryogenian” spanned a period of time from 850 to 635 million years ago.

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-    The “Andean-Saharan” occurred from 460 to 4 30 million years ago.

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-     The “Karoo” was 360-260 million years ago. The most recent was in the “Quaternary”, which spans from 2.6 million years ago to today.

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-    At least a dozen glaciations took place over the past million years, including the one we often refer to as the “Ice Age”. It peaked nearly 20,000 years ago and covered thick ice sheets across Canada, Northern Europe, and parts of South America.

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-    Scientists continue to explore the reasons why our planet has experienced these periodic chilldowns. There are many good theories about how the ice ages begin and end, including atmospheric changes, or a change in solar radiation.

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                   April 16, 2023       ICE AGE  -  cycles of Earth's environment?          3961                                                                                                                          

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--------------------- ---  Monday, April 17, 2023  ---------------------------

 

 

 

 

         

 

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