41. Volcanic ashes and tidal waves

(continued) Chapter 4.           Fast Evolution

Ashes to mud

The dynamics of hot magma erupting beneath the ocean surface differ from the kind newsreels show when lava flows down the slopes of aboveground volcanoes. In submarine eruptions the melted rock expands as it emerges from the subsurface pressure and immediately interacts with the cold ocean water, creating superheated steam. The steam, along with expanding gases residing within the magma, suffuse the molten rock’s intramolecular structure, transforming it into the bubbly sponge-like rock called pumice.


Of the cubic miles of pumice produced by the asteroid strike, vast quantities were blasted to bits ranging in size from boulders to dust. Blown clear into the stratosphere, particles light enough to remain airborne were seized by the strong upper winds to be carried around the earth and slowly rained back as dust released over time. Heavier pieces fell back to the Atlantic surface where, because of the air and gases trapped in its bubbles, it floated. Indeed, it floated in great quantities, and for a very long time.


The impact of so much porous floating rock on the ocean’s surface may be understood only in comparison to observed aftereffects of more modern eruptions of volcanoes such as Vesuvius, Mt. Etna and Krakatoa. For example, the nineteenth-century eruption of Krakatoa in the Sunda Strait – counted the second-most violent in human history – is known to have produced some twenty-four cubic miles of ejected material, and the resulting mass of pumice stone left floating in the vicinity was sufficient to interfere for some time afterward with steam ships passing that way:


Large stones containing innumerable bubbles, pumice stones, float on the sea and are slowly ground to sand by the waves.  Volcanic sand and mud cover large areas of the seabed.  The amount of the floating pumice stone is such that it often interferes with ships.  This was a disturbing consequence of the eruption of Krakatoa in 1883.

                     Svante Arrhenius: The Earth and the Sea, 1926


The prehistoric Atlantic catastrophe was thousands of times greater than Krakatoa. Its 360,000 to 480,000 cubic miles of released magma produced – after gaseous infusion – an estimated 700,000 cubic miles of pumice. If this vast quantity of pumice were spread out uniformly over the North Atlantic’s nineteen million square miles, it would form a floating layer between 200 and 330 feet thick – a floating sea of pumice rock across the ocean from shore to shore. The enormous damping effect of such a mass would essentially eliminate the ocean waves and swells that normally moil the surface and would otherwise grind it to bits. Calculations based on pumice floating in shipping lanes after the 1883 Krakatoa blast indicate the  extraordinary mass of pumice covering the entire Atlantic surface from Gibraltar to North America would have endured, slowly disintegrating for between two to three thousand years – up to 150 human generations – its particles wafting down in a seemingly eternal rain, slowly accumulating as mud on the Atlantic floor.


Such an extended blocking of Mediterranean sailors from advancing beyond the Pillars of Hercules into the formerly navigable Atlantic waters would certainly have been interpreted by contemporaries as a “sea if mud.” But did you notice? – memories of a sea of mud covering the Atlantic had already endured as a folk legend passed down orally for over 9,000 years by the time Plato learned of it nearly two and a half millennia ago. Relatively, Plato had every right to be as skeptical nine thousand years after the fact as do we today eleven thousand years after the fact, but he chose to write down without judgment or contrary opinion the information as he received it from sources that were credible in his own day. His open mindedness to the possibility that the old information was true preceded our present-day scientific bias against hearsay legends by some 2,300 years;  today’s religion-based bias against non-Biblical prehistory was moot because Christianity would not be invented until five hundred years after Plato’s lifetime.


This is why the sea is no longer navigable there and cannot be crossed in ships because this is prevented by the very deep mud, the remains of the island when it sank.

            Plato, quoting a much older Egyptian authority in the Timaeus, 360 BCE


The tsunamis

The asteroid’s crashing impact and the immediate massive lava releases and volcanic ash resulting from it were but opening scenes. Simultaneously, the impact generated perhaps the largest tsunami ever to occur during humankind’s 200,000-year sojourn as a species. And not just one tsunami but a complete ring of them. Mountainous fragments of a six-mile-wide asteroid striking near the center of the Atlantic Ocean would have instantly pushed up mountainous waves at least hundreds of feet high – and perhaps thousands, but no one will ever know – roaring away from ground zero in every direction.


…on that day all the springs of the great deep burst forth, and the floodgates of the heavens were opened…

                                                            Genesis 7:11


It’s easy to forget that the Atlantic Ocean is not a straight-up-and-down body of water lying between straight-up-and-down continents. Proceeding from north to south it in fact forms a great “S” curve wrapping around continental outlines which are anything but regular in shape. If, for instance, you fly due south from Florida – located obviously on the east coast of North America – you will arrive on the west side of South America.


If, from Gibraltar at the mouth of the Mediterranean, one draws a line westward to the northeastern-most tip of Newfoundland, everything above that line is the narrowest section of the great Atlantic ocean, the part which extends northward to the Arctic regions above Greenland and Iceland. South of that line, the Atlantic broadens enormously as its western edge descends southwestward from Nova Scotia to Florida. At Florida, the distance straight across the Atlantic to the western bulge of Africa is about twice as wide as it was where we drew our starting line. Continuing, both Atlantic coastlines now turn southeastward, skirting the edges of Brazil on the west and Africa’s Gulf of Guinea on the east, after which both sides turn southward again, growing ever broader until the mighty Atlantic merges indistinguishably into the Antarctic Ocean.


From this brief geography lesson we may deduce several obvious things.


A monstrous tidal wave originating in the Azores area of the central Atlantic and traveling outward as a ring expanding at hundreds of miles per hour would quickly arrive at several shores with utterly predictable effects. It would arrive first at the nearest land – which happens to be the land along each side of a 36-mile-long channel which connects the Atlantic Ocean to the Mediterranean Sea. Known today as the Strait of Gibraltar, at the channel’s eastern end sit those prominent limits of the old Mediterranean world known in ancient times as the Pillars of Heracles (later Hercules) – the spectacular rocky promontories of Gibraltar on the north (European) side and Jebel Musa on the south (African) side. Entered from the Atlantic, the strait’s wide mouth is funnel shaped, much like the entrance to Chesapeake Bay, narrowing to just under nine miles wide in the eastern half of the strait.


The expanding forefront of the giant tidal wave struck directly into the mouth of the Strait of Gibraltar. Roaring eastward through the narrowing funnel, the wall of water piled so high that by the time it reached Gibraltar it well may have swept clear over the top of the 1,400-foot-high limestone mountain. We have no recorded eyewitnesses, of course, but today much of the big rock is essentially barren, as if it were once scoured down to the bare rock. Much of Gibraltar today remains stony with thin, poor soil and scrubby vegetation, conditions also found across the strait at Jebel Musa (2,762 feet).


Smashing into the normally calm Mediterranean, the torrent now pushed up those waters into a gigantic bulge sweeping eastward through the length of the Mediterranean Sea. A mountain of water roared over the north African coastlines of present-day Algeria and Tunisia, across Corsica, Sicily, Italy and Greece. East of Greece the great wave pushed northwestward into the Aegean, in a moment gouging out the Bosporus-Dardanelles channel so the waters quickly flooded into the Black Sea basin. Continuing eastward, the gigantic wall grew even higher as the waters piled up above the sloping seafloor at the Mediterranean’s eastern end, raging ashore across the entirety of modern-day Syria, Lebanon, Israel and Jordan. Noah’s great flood then followed the lay of the land, roaring eastward across the old fertile crescent land between the Tigris and Euphrates rivers, and on down into the Persian Gulf, its irresistible force continuing into the Arabian Sea and Indian Ocean.


The reality was of course much messier than this brief recitation, such that, throughout the Middle East, few indeed were the areas not directly touched by the almighty tidal wave. Only on mountainous heights would a few fortunate survivors, who happened to be grazing their sheep and goats on upper pastures that day, witness what was happening below, becoming the progenitors of a flood legend which would endure for 11,000 years.


Simultaneously, segments of the great wave had crashed into the European and African coastlines to north and south of the Gibraltar Strait – other nearby “first-contact lands” in the great wave’s path – advancing far across the terrain until mountains and friction impeded their advance. To the south, there is evidence that the wave swept across the entire length of the land today known as the Sahara Desert, ensuring the eventual complete desertification seen today, and on across Egypt into the Red Sea.


North of Gibraltar, above the Pyrenees, the giant wall of water roared across hundreds of miles of shoreline onto the low flat plains of northern Europe. With little impedence, floodwaters in a wall initially hundreds of feet high picked up soil and silt as it flowed irresistibly across the northern plains in the west of Europe, then central Europe, and thence across the plains of Poland and Russia to the steppes of western Asia, around the ends of the low mountain bulges of central Asia and on across eastern Asia into the Pacific Ocean.


Today a gigantic deposit of extraordinarily fine clay known as loess, consisting of the very smallest particles of silt and disintegrated soil particles, spreads in a great swath thousands of miles across southeastern Siberia – shaped like an elongated fan, as if a giant bucket had been dumped – gradually widening as it proceeds on across the north China plain. Hundreds of feet thick in places, this unusually rich soil has fed China for millennia. For comparable thousands of years people have carved out shaped cavities – easily-built homes – in the loess carried from Europe nearly eleven thousand years ago.


Westward rushed the western side of the great tidal wave until it crossed the shores of modern Canada, United States, Caribbean isles and Mexico, and thence on southward to the coastal lowlands of South America.


In all the places mentioned here, in a great swath surrounding the Atlantic Ocean, native peoples in many different languages all repeat a legend of a great flood which occurred at some distant time long ago, an old true story, they say, passed down from their very remote ancestors. Often the stories have evolved over time, precisely like the game of gossip, until the characters have taken on old names, and changed and changed again, some assuming the characterization of old gods and old heroes – such as Utnapishtim and Noah. But they all share a sameness – a great flood happened, all perished but a few survivors. The sameness persists around the Indian and Pacific basins too, though in somewhat less degree. The trans-Asiatic wave which deposited the loess and endured into the north Pacific, accompanied by secondary waves reflecting back up from the southern oceans into the Pacific and Indian Oceans, created havoc and legends there as well.


And even that is not all. If you heft the biggest, heaviest rock you can manage to lift, and if you then stagger over and drop it off a pier into a pond, you might notice that primary, secondary and tertiary effects follow. In quick succession after the initial Ka-Whop!, the rock goes down while the water rises up. The water in fact rises up into a ring a foot or more high, and this ring instantly roars outward even while a secondary up-and-down motion is initiating a second wave, not quite as big as the first, which also speeds outward. This will happen at least a third time, producing a tertiary wave a bit smaller still, but still big enough to do some damage if it were in the neighborhood of a hundred feet high. Still more waves are thusly generated, but they peter out fairly quickly after the first three have propagated away from the drop site. If the dropped rock were a large asteroid, even these would be enormous compared to “ordinary” tidal waves.


This waves-in-succession scenario is what happened immediately after the mid-Atlantic asteroid strike, meaning that all the disastrous tidal-wave smashes previously described happened a second time, slightly diminished, and a third – and so on. No living thing anywhere near any coastline, or in the way of mighty tidal waves raging across whole continents, could possibly have survived. The few humans who were high enough and lucky enough to survive – and to further survive the extended famine times which followed – would have been mightily impressed. They would tell the story to their children, over and over, and with such deep seriousness that the children would know it was as true as it was dreadful, and they would tell their children too.


But this flood was by no means limited to the tidal waves. They were just the beginning of the catastrophe which hit the earth, nearly eleven thousand years ago.



*          ©          *


…to be continued in one week…


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