The Younger Dryas period was named after the alpine and tundra wildflower Dryas octopetala (pictured above). A thousand years earlier, there was another cold period, or "stadial," that lasted only 300 years — the Older Dryas.

Why did the Younger Dryas happen? One source explains: "The prevailing theory holds that the Younger Dryas was caused by a significant reduction or shutdown of the North Atlantic thermohaline circulation in response to a sudden influx of fresh water from Lake Agassiz and deglaciation in North America. The global climate would then have become locked into the new state until freezing removed the fresh water 'lid' from the north Atlantic Ocean." [Wikipedia]

Scientists are still uncertain why the Younger Dryas ended, and equally uncertain why the end was so abrupt.

EVIDENCE
Freezing may have removed the "freshwater lid" from the North Atlantic. The cold of the Younger Dryas would certainly have been a viable source of the required freezing. But there is more evidence to consider.

We know now that the Younger Dryas ended about 9600 BCE. To this author, that date looked hauntingly familiar. It matches the date given by Plato in his Timaeus dialogue for the destruction of Atlantis. That by itself is nothing more than an interesting coincidence. Well, maybe more than merely interesting, but far from proof of anything.

If Atlantis existed, and if it collapsed as Plato described (in one day and a night), then there would likely have been a massive mega-tsunami coursing across the Atlantic, stirring up silt, the thermohaline "cap," and washing a great deal of topsoil back into the ocean. These actions might have stopped the Younger Dryas, and created the muddy ocean to which Plato referred.

Graph from the 1989 article.[1] It shows Barbados sea level curve based on radiocarbon-dated A. palmata (filled circles) compared with A. palmata age-depth data (open circles) for four other Caribbean island locations.

DISPLACEMENT
Besides the mega-tsunami, the other great effect of such a subsidence would have been the "reverse displacement" of more than a million cubic kilometers of ocean water. This is one of those Archimedean "eureka" moments, only we are not talking of an old Greek getting out of a bathtub. We are talking about a Texas-sized plot of land effectively removing itself from the ocean. Tectonic collapse would have lowered sea level worldwide. But how much? And is there any evidence for such an occurrence?

In 1989, an article appeared in Nature detailing the effects of glacial melt on sea level rise.^[1] When the article was written, dates were not as accurate as they are currently. It was estimated then that the Younger Dryas ended about 10,000 years BP (before 1950, the "present" for all C14 dates). On the graph accompanying that article (shown here), there is a period of relative flattening near the middle. This represents the Younger Dryas. At the end of that period, there is an approximately two meter drop in sea levels. Afterward, the graph steepens as climate leaves the Ice Age behind.

A sea level drop of two meters worldwide is consistent with a Texas-sized plot of land subsiding in the ocean to a depth of 3000 meters. This depth is in agreement with much of the ocean floor around the Azores Islands.

Still, this does not prove anything. One data point out of alignment may be from an error in recording, "noise" in the data, or the result of some unrelated phenomenon. All this means is that more research is needed to pin down the "blip" as an artifact of reality, a proxy for some actual event. Any takers?

VOLCANIC TRACE
Data from the Greenland Ice Sheet Project (GISP) produced several ice cores detailing the climate of Earth over the last 100,000+ years. GISP2 was a follow-up project that drilled at a glaciologically better location and produced a core more than 3000 meters in length. The data in the table, below, is from that project.

The highlighted data point indicates a minor spike in the volcanic pollution produced at that time. The age (11,569.77 years) is calculated from the "BP" base date of 1950. So the date in real years would be calculated as 9620.77 BCE. Compared to the great volcanic eruptions of the past, this is indeed minor. It is roughly one-sixth the Greenland deposit of debris from the Toba eruption (69,000 BCE), and that massive blast was on the other side of the planet. This 9620.77 date is slightly before the nominally accepted end of the Younger Dryas, but a great deal of significance cannot be placed on exact sequences. The time resolution is not that sharp (yet).

What does this mean for our story? If Atlantis existed, and it subsided 9620 BCE, there may have been some volcanic debris that made it to Greenland. But wouldn't such a violent event have resulted in far more volcanic pollution in the ice core? Not necessarily. We do not know that any volcanic plume would have to have occurred. Too, the event was relatively brief. The more active portion of it might have been only part of Atlantis's last day. As the landmass subsided, volcanic material might have come in contact with sea water, creating a sizeable plume of steam. This steam, in turn, may have precipitated out a portion of the volcanic cloud before it could drift beyond the region. This, of course, is speculation, but the 9620.77 BCE event proxy could at least plausibly be related to the Atlantis subsidence.

A minor little spike in GISP2 volcanic ice cores markers

Age (yr)	Total sulfate (ppb)	Volcanic sulfate
11,557.19	51.13	2
11,559.40	44.79	0
11,561.44	35.03	0
11,563.57	31.96	0
11,565.69	48.73	0
11,567.73	82.07	15
11,569.77	134.10	79
11,571.90	31.98	0
11,573.94	32.71	0
11,575.98	35.97	0
11,578.10	23.67	0
11,580.14	34.67	0
11,582.18	42.16	0
11,584.22	44.65	0

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¹Fairbanks, R., "A 17,000-year glacio-eustatic sea level record: influence of glacial melting rates on the Younger Dryas event and deep-ocean circulation," Nature, Vol. 342, 7 December 1989.