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Swift
2017-Mar-15, 03:09 PM
From Harvard U (https://www.seas.harvard.edu/news/2017/03/perfect-storm-of-fire-and-ice-may-have-led-to-snowball-earth)

What caused the largest glaciation event in Earth’s history, known as ‘snowball Earth’?

Geologists and climate scientists have been searching for the answer for years but the root cause of the phenomenon remains elusive.

Now, Harvard University researchers have a new hypothesis about what caused the runaway glaciation that covered the Earth pole-to-pole in ice. The research is published in Geophysical Research Letters.

Researchers have pinpointed the start of what’s known as the Sturtian snowball Earth event to about 717 million years ago — give or take a few 100,000 years. At around that time, a huge volcanic event devastated an area from present day Alaska to Greenland.

Coincidence?

Harvard professors Francis Macdonald and Robin Wordsworth thought not.

Link to Geophysical Research Letters abstract (http://onlinelibrary.wiley.com/doi/10.1002/2016GL072335/abstract?campaign=wolacceptedarticle)

We propose that the first Neoproterozoic Snowball Earth event, the Sturtian glaciation, was initiated by the injection of sulfate aerosols into the stratosphere. Geochronological data indicate that the Natkusiak magmatic assemblage of the Franklin large igneous province coincided with onset of the Sturtian glaciation. The Natkusiak was emplaced into an evaporite basin and entrained significant quantities of sulfur, which would have led to extensive SO2 and H2S outgassing in hot convective plumes. The largest of these plumes could have penetrated the tropopause, leading to stratospheric sulfate aerosol formation and an albedo increase sufficient to force a Snowball. Radiative forcing was maximized by the equatorial location of the Franklin and the cool Neoproterozoic background climate, which would have lowered the tropopause height, increasing the rate of stratospheric aerosol injection. Our results have implications for understanding Phanerozoic mass extinction events, exoplanet habitability, and aerosol perturbations to the present-day climate.

Article from R&D magazine (http://www.rdmag.com/article/2017/03/fire-and-ice-effect-may-have-prompted-snowball-earth?et_cid=5873180&et_rid=54636800&type=image&et_cid=5873180&et_rid=54636800&linkid=content)


Geological and chemical studies of the region—called the Franklin large igneous province—revealed that volcanic rocks erupted through sulfur-rich sediments, which would have been pushed into the atmosphere during eruption as sulfur dioxide.

...

The research team demonstrated that about 10 years of continual eruptions from these types of volcanoes could have poured enough aerosols into the atmosphere to rapidly destabilize the climate.

“Cooling from aerosols doesn't have to freeze the whole planet; it just has to drive the ice to a critical latitude,” Macdonald said. “Then the ice does the rest."

danscope
2017-Mar-15, 07:34 PM
WOW!!! Ten years of continuous volcanism . So.... was Yellowstone considered the prime culprit / source of the eruption?

Best regards,
Dan

Swift
2017-Mar-15, 08:08 PM
WOW!!! Ten years of continuous volcanism . So.... was Yellowstone considered the prime culprit / source of the eruption?

Best regards,
Dan
I don't know if hotspots have great, great grandfathers, but I think the short answer is "no".

According to this website (http://www.yellowstonegis.utah.edu/research/hotspot.html), the Yellowstone hotspot is only about 20 million years old.

717 million years ago is I think at least two supercontinents (and their breakups) ago.

danscope
2017-Mar-15, 08:18 PM
Sounds plausible, going back that far.

bknight
2017-Mar-16, 02:17 AM
It is interesting that the end of snowball Earth is postulated by volcanic placing greenhouse gases into the atmosphere.

danscope
2017-Mar-16, 05:32 AM
Mother Earth gives, and Mother Earth taketh away .

BigDon
2017-Mar-16, 09:25 PM
Not "the cause" but another big piece of the puzzle.

One mustn't forget that all the continents were on the equator at that, and other future snowball Earth periods. This is BAD because there is minimal ocean heating and lots of polar water to freeze into nice bright white icecaps.


It is interesting that the end of snowball Earth is postulated by volcanic placing greenhouse gases into the atmosphere.

No, the volcanism broke up the equatorial supercontinent and moved the pieces away from the equator.

bknight
2017-Mar-17, 12:52 AM
...



No, the volcanism broke up the equatorial supercontinent and moved the pieces away from the equator.

I believe that plate tectonics separated the super continents. Now it may/may not have been at a line of volcanism, but plate tectonics is the chief mover of land masses.

geonuc
2017-Mar-17, 09:18 AM
If you're interested in the relationship between the Franklin Large Igneous Province (LIP) and the Sturtian Snowball Event, a paper by Macdonald et al. laid the groundwork and proposed models to nail down if there was a causal mechanism. Macdonald was one of the authors of the research letter linked in the OP.

LIPs are interesting because many are huge and lasted for long periods of time - sometimes hundreds of thousands or a million years. That's a lot of out-gassing. The Franklin event was one of the larger ones and coincided with Rodinia, a supercontinent that preceded Pangea (there was one other between the two).

http://www.largeigneousprovinces.org/15feb

BigDon
2017-Mar-17, 05:57 PM
If you're interested in the relationship between the Franklin Large Igneous Province (LIP) and the Sturtian Snowball Event, a paper by Macdonald et al. laid the groundwork and proposed models to nail down if there was a causal mechanism. Macdonald was one of the authors of the research letter linked in the OP.

LIPs are interesting because many are huge and lasted for long periods of time - sometimes hundreds of thousands or a million years. That's a lot of out-gassing. The Franklin event was one of the larger ones and coincided with Rodinia, a supercontinent that preceded Pangea (there was one other between the two).

http://www.largeigneousprovinces.org/15feb

I love bringing up the subject of LIPs to alarmists who think humanity is the absolute worst thing that's ever happened to Earth. The Deccan Traps, for instance, had the output of a Mount Saint Helens explosion weekly, for over 100,000 years.

That's so over the top most of them just fall back on the ever popular "N'uh!" defense.

Makes British coal burning in the 1800's seem silly in comparison

slang
2017-Mar-17, 08:47 PM
"Alarmist" is an insult towards the scientists in the global warming topic. Please stop that, infraction issued. You know better.