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