this point in time the continental map looked something like this. This
massive ice sheet had been in retreat and vegetation which had
been driven south in the Wisconsian Glaciation was recolonizing the
north. During the most recent Ice Age a corridor supposedly developed
linking Alaska with southern lands and this was once considered the
sole route used by migrants from Siberia. The inserted diagram shows
that there have been many periods when life forms were compromised by
too much heat or cold. Homo sapiens
(upper green dot) arrived late in the geologic history of planet
earth. Several doomsday scenarios have followed sudden climate
change. The Clovis People arrived at the end of the last Ice Age, and
all recorded history has taken place on that final warming trend not
yet fully realized.
If the inset map is correct humans were probably prevented from coming to North America by land in times past. The red dot locates the Debert settlement site and makes it clear that human habitation was impossible in the early years of paleoindian incurson from Asia. The ice piled up on the land was less here than elsewhere but formidable.
This regional map shows the ice cover before much settlement took place in New England and Atlantic Canada. Dotted lines indicate ice ridges, the hight points of the pile up. Solid lines indicate drainage paths taken by wter as the glacial ice melted following a time closer the "Thermal Maximum." Back then planet earth was warmer than at present. Moving ahead a few thousand years...
This regional map shows the ice cover as regional glaciers . The Debert Paleoindian site is in orange as is Lunenburg. Frigid ice-strewn waters surrounded land masses, which were then much higher above sea level because so much water remained in solid state. The crust of the earth had been depressed and was now in rebound but that deformation is clearly seen in flooded areas of New England and New Brunswick. Those large offshore islands, with the exception of Sable) are now below sea level and constiute our shallow productive fishing banks.
Mikmaq legend says that these people moved here from the south west. It will never be known why they relocated climatically challenged north, choosing to hunt caribou rather than giant elephants. Whatever their reasons for coming here, men began to move into the north east just as the climate was leaning to the cool side. A major encampment in Nova Scotia was near Debert, at the head of the Bay of Fundy. It was discovered in 1948 but was only excavated in 1962 and 1964. This is the oldest and best recorded site in Atlantic Canada and stone hunting tools found there have been found to resemble those of the western Clovis.
Debert is a prime Clovis archaeological site.The butchering tools found at Debert make it clear that the people who lived here Were big-game hunters but the acidic soil has long since destroyed the remains of their hunts. A study of Paleofossils has shown that the region was a mix of tundra and trees. In 1989 two additional Paleoindian camps were discovered a kilometre away at Belmont, Nova Scotia.More than 5,000 stone artifacts have been recovered from these sites.
These were huge creatures were hunted in the south west of North America. There might have been mastadons in Nova Scotia and New Brunswick, remains have been found from much earlier eras in time. This one comprises the most complete skeleton recovered in Canada and is now in the N.B. Museum at Saint John. However, these sites have interpreted as "seasonal hunting camps...ideally situated to intercept herds of migrating caribou." The blood residue found on some tools led to a tentative conclusion that caribou was an important part of the diet of these folk although they must have had access to other large and small game animals, fish and fowl.
There has been a lot of work done since these sites were uncovered. See stessurficial.ca for a less superficial account. Rod has added that red arrow more clearly indicate the Debert/Belmont site.This is not only the oldest place occupied by humans in Nova Scotia but the most northeasterly Paleoindian site positively identified as occupied for a lengthy period.
The Belmont site has been found to be sandwiched between two different layers of sand which are thought to have been wind-born. The lowest layer is thought to have been a glacial lake bottom. The upper layer is considered to represent a regenerated glacial lake; leading to the suspicion that these sites were abandoned in response to the local redevelopment of ice caps.
Even where these folk were in residence the mean temperature was 10º-15º C lower than it is today. Sea level was as much as 60 feet lower making Prince Edward Island a part of the mainland. It has been guessed that groups of 30-40 people constituted a usual camp and that they moved in reponse to migrating herds. It is also thought that they made clothing and small behive-shaped shelters for themselves using the hides of caribou. The stone awls left behind were probably used to penetrate the skins so that they could be sewn together with sinews or strips of leather.
There is no question that some of the Clovis people did hunt mammoths, but caribou and similarly sized creatures must have been far easier game. But mastadons, camels, horses and those ravaging predators have not turned up in ancient bone piles. In historic times the Indian population of our own region has never been huge and massive killings were never needed to sustain these inhabitants. The Clovis people seem to have been even more widely spread? Outsized animals in parts of the north included not only the gigantic Shorfaced Bear but the Dire Wolf, the Giant Beaver, Mastadons (smaller cousins of the Columbian Mammoth the Woolly Mammoth, the American Scimitar Cat and Jefferson's Ground Sloth. Most of these animals were as big as (and even more dangerous than) the vegetarian mastadon.
Well worth a look! "Possible"means a bit on the unlikely side. An unqualified"Yes" is given to the black bear, ordinary beaver, caribou, and the walrus, all animal which modern man would rate as less than terrifying.
And very close to a precipitous glacier. With the rose of the land Glacial Lake Aldershot eventually became the dry land now known as the Annapolis Valley. All those green areas have since been weathered and eroded out of existence and are under the salt waters of the Bay of Fundy.
This climate would be bad news for the the flora, fauna and megafauna of Pleistocene North America. These last were "very very large mammals." The smallest weighed about 45 kilograms (100 pounds) and the largest 4,500 kilograms (10,000 pounds). Climate can degrade in the opposite direction and when the Clvis Peopled arrive here in was already on a rollercoaster ride down from a pervious "Thermal Maximum" when it had been too hot for comfort in a lot of parts of planet earth.
Aboriginal tales may remember the fall in air temperatures which spelled very hard times for plant and animal life. Average temperatures all over the world started to slip 12,900 years ago and that continued for about 1,300 years. This was a relatively short period judging by other stadials or "Big Freezes"and here is what happened in the vicinity of the Debert settlements. Conditions were not as extreme in North America as in Europe, but the transition back to a glacial climate was sudden, and took place in a matter of a few
In Britain the mean annual temperature dropped by -5ºC and on the sub-continent of Greenland it went down by a full 15º. Localized ice fields, like that above, returned in Atlantic Canada and the movement of temperate plants and animals into the area was cut short. In the eastern United States deciduous forest cover had come as far north as Maine, but this was again replaced by boreal forest as the cold advanced. This happening sometimes called the Younger Dryas Event sent waters rushing into a lowland area which in much more distant times had been a basin for the saline Windsor Sea. The Atlantic Ocean is the white area at the bottom of this map.
Recent DNA testing of native populations veers away from a former theory that the major genetic input was East Asia and suggests that most characteristics are from that gene pool. The Clovis Peole of Nova Scotia vanished suddenly and their connection with the Mi'kmaq is more tenuous than that with Native Americans located at this unfortunate time in more southernly parts of the Americas. There is no way of knowing, since DNA of Debert humans will probably never be found.
This graph is thought to reflect conditions in other jurisdictions. It is based on sampling Greenland Ice cores. Note that these dates are BCE and 2,000 has to be added to each to correpond with BP dates.
This additional information may be relevant since both plants and animals make use of oxygen, albeit in different ways. These dates are BPand place to lowesr readings at the time of Younger Dryas.
This is a present-day map with the areas most affected by the Younger Dryas cooling (light blue) indicated. Areas also impacted to a lesser degree (purple) are shown in western America. There were other regions where a lesser effect was noticed, e.g. Central America; but this admittedly was a somewhat restricted disaster, if there is such a monster. Why was it regional?
If anything, the situation was more dire across the Atlantic.
It is an inconvenient fact that scientists have to publish to survive, and sometimes they get too much non-critical publicity from the popular press. In this instance, it was claimed that this hypothesis ended the arguments overcausation. In this illustration Lake Agassiz , which did exist, was greatly oversized but its supposed massive breakaway action certainly backed aboriginal "world flood" legends. Sadly, for those at a Quebec-based research unit this idea did not hold water.
It appears that the lake as well as the research was just not that deep, although the idea made a great story. To be fair, this image is also imaginery; that's the stuff of geology and most sciences. It's always a good idea to wait a bit for peer reaction before going overtly public.
If only the explanatioms of loss were this simple! "Five Great Extinctions are recognized as opposed to "Lesser Extinctions," not global in scope. Today the causes are guessed to have been mutlifactorial: The extinction of 85% of all marine species in the Ordivician is accepted as being an effect of dramatic fluctuations in sea level. The Late Devonian Event which saw another 83% of marine life killed off is seen as a combination ofglobal cooling combined with a loss of oceanic oxygen. Currently some sort of extraterrestial impact and severe volcanic activity in the Permian may have aided dramatic fluctuations in sea level and climate change; 82% of marine life eliminated. The Triassis Event is suspected as having been related to vulcanism producing global warming.
Best known is the Creataceous (Cretaceous/Triassic)Event which killed off the dinosaurs and is seen as caused by extraterrestial impact and severe volcanism. Both happenings filled the air with ejecta and harmful gases resulting suddenly in a colder earth where flora and fauna supporting these huge creatures was seriously reduced. This theory was not much believed before the Chicxulub crater was discovered on land and in water at the Yucatan Peninsula in the late 1970s.
It was formed by a large asteroid or comet at least 10 kilometres (6 miles) in diameter impacting the Earth. The date of the impact coincides precisely with the at the boundary between the K-T boundary and it is now a widely accepted theory that worldwide climate disruption from the event was the cause of the extinction in which 75% of plant and animal species on Earth suddenly vanished, including all non-avian dinosaurs. The immediate effects are nicely summarized in the above illustration.
The effect was somewhat like a nuclear blast and all that released energy resulted in devestation of plant life and its regrowth was impeded by a sunless sky.
The crater is more than 110 miles in diameter and 12 miles deep This is the third of the largest confirmed impact structures on Earth. Larger are Vredefort crater in South Africa, 300km, and in Canada, Sudbury Basin, 250km.
There are 190 confirmed craters given in the Earth Impact Database. That big one collided with our planett between 4.4 and 4.45 billion years ago; and the Canadian one 1,847-million years BP. Neither seems directly implicated in a "Massive Extinction Event."
The survivors of the Cretaceous/Tertiary catastrophe included some small, squirrel-like animals that were to give rise to the dominant life forms of the next era - the fur-bearing, warm-blooded mammals that eventually gave rise to the human species. The period between the extinction of the dinosaurs and the present day is sometimes called the Age of Mammals or Cenozoic.
The impact of a large asteroid or comet could have caused food chains to collapse both on land and at sea by producing dust and particulate aerosols and impacting photosynthesis. Sulfur-rich rocks could have emitted sulfur oxides creating poisonous acid rain, contributing further to the endangerment of food chains and animals. There nay also have been megatsunamis and global forest fires.
Most paleontologists now agree that an asteroid did hit the Earth as outlined above, but there is an ongoing dispute whether the impact was the sole cause of the dinosaur extinction event.
Asteroids are out there in quantity and may fall to earth leaving a colourful trail which varies with their chemistry.The current belt consists primarily of three categories of asteroids: C-type or carbonaceous asteroids, S-type or silicate asteroids, and M-type or metallic asteroids.Some of the debris from collisions can form meteoroids that enter the Earth's atmosphere. Of the 50,000 meteorites found on Earth to date, 99.8 percent are believed to have originated with the breakaway of of planetesimals in the asteroid belt. Some have theorized that life was seeded by a primordial Asteroid-Earth collision.
It is lucky that this shooting-star did not make meteorite status or damage would have been greater. The Chelyabinsk meteor was estimated to be about 20 m in diameter with an airburst of around 500 kilotons, an explosion 30 times the one over Hiroshima. One thousand people were injured by this meteor airburst event.
Above, more great news for 2016! The late Eugene Shoemaker of the U.S. Geological Survey estimated that an event about the size of the nuclear weapon that destroyed Hiroshima occurs about once a year. While spectacular, they generally go unnoticed because the the Earth's surface is largely covered by water, a good portion of the land surface is uninhabited and the explosions usually occur at high altitude.
Causation is probably a linked series of unfortunate events as this diagram suggests, but there are quite a few scientists who think extraterrestial imapact has played some part in all extinctions. But these folk have had a problem producing a "smoking-gun" as evidence.
This may have been a regular "background extinction event," but Debert's flora, fauna and people were all affected in a major way. Methane is a natural substance sometimes produced biologically. It contribes more to global warming than carbon dioxide. In this case death and decay is indicated by its decline, matched by a cooling trend in air temperature.
Mass extinction events have seen the elimination of large numbers of plant and animal species in relatively short periods of geological time. Largely as a result of five such happenings, 99% of species once in existence are now extinct. Although the most massive losses have taken place in remote times, the Quaternary Epoch has been noteworthy for the loss of numerous large species of animal. Because this began near the beginning of the Holocene (the present ) Eooch, it is sometimes called the Holocene Mass Extinction Event. Plaeontologist have tried to explain what happened in terms of climate change, the onset of novel diseases, and overkill by human hunters. It is estimated that about 140,000 species have continued to vanish each year whatever the cause.In some cases today that's due to "collateral damage" by humans.
The Younger-Dryas Stadial or "Big Freeze" was only a part of the more general Holocene carnage, but is noteworthy for being the time when the really big Megafauna fell prey to extinction. Earlier on, a hypothesis was introduced suggesting that their disappearnce was due to human advances in hunting techniques resulting in overkill. University of Arizona ecologist Paul Martin was the first to propose this idea in 1967. In brief, it says that the Paleoindians were responsible for these extinctions. A problem here is found in the fact that some of those big, hulking creatures had gone to ground before immigrants arrived in North America. Only about 15 genera of 33 genera remained for them to bring down.
Between 15,000 BP and 10,000 BP there had been an upward march in the world's mean temperature of about 6ºC, a situation somewhat like that now in the works. There is a hypothesis that animals that developed in the shadow of the Wisconsin ice sheet were simply not able to adapt to thic climatic inter-stadial change, but there is no hard evidence for that. Not all those big animals in North America lived in the north. A hotter environment changes rainfall patterns and the types of vegetation available to sustain herbivores who are the basis of the food chain. Again, the megaherbivores managed to survive earlier changes of this kind and some actually prospered when woodland was converted to grassland. In any event, the usual vegatation did not vanish, and most herb-eaters had four legs and a good ability to change their range.
This does not rule out the idea that human kills and climate change might have helped bring down the big beasts. The hyperdisease hypothesis proposed the idea that invading humans passed new bacteria and viruses to the animal populations. From what is known there is usually an intermediate host in such transfers and the dog was suggested. However, no evidence of a disease virulent enough to have killed off so many species is on record.
It has also been hypothsised that humans simple killed off so many "natural" predators when they arrived, the largest animals overpopulated the landscape and fell prey to ecological imbalance. There is, however, no evidence that humans were particularly driven to take on those massive sabretooth beasts, direwolves and giant crocodiles let alone smaller probably inedible carnivores. The second-order predation hypothesis did not survive as a single explanation of these losses. Of these, the Blitzkrieg Hypothesis or overkill idea, is the one largely discredited by most paleontologists and other scientists.
Obviously, something set off a chain of unfortunate events, but probably not a nuclear war. That said, there was a sudden change of climate in eastern Canada and northwest Europe and nuclear warfare is predicted to bring on global winter. That event 12,800 to 12,000 years ago did bring on a glacial readvance although ice did not override Debert at this time. Ice dams built up between the Cobequid Highlands and silty-clay and sand was deposited in new lakes. Overlaying laminated sands is a massive "structureless sand deposit" in which artifacts were found. These overlay another massive layer of silty clay. The question of whether this was the result of a bang or a whimper will probably be resolved.The Younger Dryas was underway.
This has led to the Comet Hypothesis, first propsed at the 2007 meeeting of the American Geophysical Union in Mexico. Some scientists there suggested that the extinction of of those large North American animals might have started with an incoming comet 12,900 years in the past.
Difficulties with this proposition centred on the seeming lack of an impact crater similar to that which produced that notable earlier extinction. The so-called K-T Mass Extinction left a layer of iridium-rich clay at the Creaceous-Triassic rock boundary . This could only have derived from a extra-terrestrial body and was used to postulate that a very large body had collided with our planet.
No iridium was found at the Quaternary-Holocean Boundary. However, in January 2009 nanodiamonds, which are associated with asteroid impacts, were recovered from the soil of six sites in North America and two in Canada. These were of appropriate age and provenance to suggest that there had been collisions between extraterrestial bodies and the earth.
This on line application actually exists to humour those with morbid curiosity. "Every billion years or so...." That's the effectof collision with a comet. How about a house-sized asteroid? And that leads us to Part III: Nova Scotia Doomsday. The Bloody Creek Tale.