From Planet Oregon.com
Elaine Meinel Supkis
8,000 years ago, camels and giant sloths ran around in Arizona which wasn't so arid back then. They all went extinct very suddenly when something odd happened back then. The whole world underwent some pretty sudden and violent see-saws back then and this has bearing on today since the forces at work were varied but human were the keystone, we are the domesticators and the destructors for this is the same period we figured out how to domesticate many plants and animals.
Workers digging at the future site of a Wal-Mart store in suburban Mesa have unearthed the bones of a prehistoric camel that's estimated to be about 10,000 years old.
Arizona State University geology museum curator Brad Archer hurried out to the site Friday when he got the news that the owner of a nursery was carefully excavating bones found at the bottom of a hole being dug for a new ornamental citrus tree.
"There's no question that this is a camel; these creatures walked the land here until about 8,000 years ago, when the same event that wiped out a great deal of mammal life took place," Archer told The Arizona Republic.
So many forces were at work in that critical phase, 8,000 years ago. Evolution doesn't happen unless ecological niches suddenly change or are invaded. So when we see sudden extinctions, this means the enviroment changed and niches could no longer be inhabited. And usually, this also means other life forms evolve rapidly as they invade previously-occupied niches.
So let's look at the climate 8.000 years ago: according to many studies, the last Ice Age ended suddenly around 11-10,000 years ago. The massive glaciers melted rapidly. Now, in previous ice-melts, the large Ice Age fauna would simply move north but 8,000 years ago, most of them went extinct. With incredible speed.
This figure shows snow accumulation and isotopically inferred temperature records in the Greenland GISP2 ice core and a temperature record derived from oxygen isotope measurements of fossil shells in the sediments of Lake Ammersee, southern Germany. These records all show a major climatic instability event which occurred around 8200 years ago, during the Holocene. The event was large both in magnitude, as reflected by a temperature signal in Greenland of order 5 �C, and in its geographical extent, as indicated by the close correlation of the signal in these two locations. The dramatic event is also seen in the methane record from Greenland (not shown here) indicating possible major shifts in hydrology and land cover in lower latitudes. source: Von Grafenstein et al (1998) Climate Dynamics, 14, 73-81.
Not only was there a brief, sharp drop in temperatures but there was also a decrease in snowfall in Greenland. The sharpness of this event, the suddeness is curious. People propose all sorts of things like the ocean suddenly changing its course as the Gulf Stream moves southwards, for example. But even if that were so, it wouldn't be so brief as well as sudden. And if the Gulf Stream changed course frequently, this would be periodic, it would occilate.
But this is sudden, brutal and brief. And it coincides with many singular and amazing events and changes in the way the ecosystem worked. So I decided to line up some of these events that could have triggered such a change.
We know that the earth has an eccentric orbit and tilt which probably is an artifact of when something really, really big slammed into the earth and created the moon 3 billion years ago. Because of this, the amount of sun shining on parts of the earth varies greatly over a 23,000 year cycle.
The third cycle is due to precession of the spin axis (as in a spinning top) and occurs over a ~23,000 year cycle. Presently, the Earth is closest to the Sun in January and farther away in July. Due to precession, the reverse will be true in ~11,000 years. This will give the Northern Hemisphere more severe winters.
When all the Milankovitch cycles (alone) are taken into account, the present trend should be towards a cooler climate in the Northern Hemisphere, with extensive glaciation. The Milankovitch cycles may help explain the advance and retreat of ice over periods of 10,000 to 100,000 years. They do not explain what caused the Ice Age in the first place.
Other factors which work in conjunction with the Earth's orbital changes include:
The amount of dust in the atmosphere
The reflectivity of the ice sheets
The concentration of greenhouse gases
The changing characteristics of clouds
The rebounding of land, having been depressed by ice.
I have lived through several significant but of course, none were huge, volcanic events and each time, the sun rises and sun sets are spectacular and it changes the climate drastically. When Mt. Pitumbo in the Philippines blew out a large amount of dust, it made things significantly colder insantly. I was living in a tent on my mountain. The previous year was very warm and that winter, hardly any snow.
Then the volcano blew. I could see the fine white dust in the high statosphere. Immediately, it was cold. It was early June and we wore coats and the wind blew hard. World temperatures dropped over 3 degrees F. Then we had amazing amount of snow that winter and the following summer was cold because of red dust from Mongolia which gave sunny days a brass sheen to the sky.
It wasn't a great volcanic event but the Mt. Toba eruption in 1812 made it so cold in Berlin, NY, there was snow all summer in the mountains and people nearly starved to death.
Right now there is furious debate about the impact of human activities on global warming. It is the sun, the tilt of the earth, changes in agriculture? What is warming up the planet? The interaction between climate and humans balancing or unbalancing each other goes way back to when there were not so many humans on earth, a key climate change was when the last Ice Age suddenly ended and then suddenly became extremely cold 8,000 years ago and then has basically warmed up as humans terraformed this planet increasingly. What is going on here?
Methane gas released by peat bogs in the northern-most third of the globe probably helped fuel the last major round of global warming, which drew the ice age to a close between 11,000 and 12,000 years ago, UCLA and Russian Academy of Sciences scientists have concluded.
Methane released by the massive northern peatlands complex in western Siberia contributed to global warming at the end of the Ice Age. (Credit: Karen Frey)
But the new information in no way lets human sources of greenhouse gases off the hook for the present round of global warming, warn the team of researchers whose findings appear in the Oct. 13 issue of Science.
Just because something happens and then something else happens doesn't mean these things were the exclusive or even the most important causes of other events. All things influence each other and releasing gas from bogs can add chemicals to the atmosphere which has an effect but the cyclic nature of the Ice Ages and how they began in recent times, geologically speaking, means the cycles can't be simply organic.
We already suspect major literally earth-shaking events leads to evolutionary death spirals and evolutionary swings, things like asteroids and meteorites have periodically wiped out many of the existing life forms in the past. So 8,000 years ago, something was afoot.
Past orderly climate cycles support this new hypothesis: during past periods that followed glaciations, temperatures rose, peaked, and then fell to a threshold that triggered the next glaciation. During these interglaciations, atmospheric levels of two greenhouse gases (GHGs), methane and CO2, rose, then fell.
But following the last glaciation, temperatures rose as expected, then started to fall but did not continue to fall. Levels of CO2 and methane rose and continued to rise when they should have fallen.
This deviation from natural trends was caused by humans. Notably, agriculture employing irrigation, particularly wet-rice farming, started boosting methane levels around 5000 years ago. Deforestation and biomass burning started boosting CO2 levels around 8000 year ago. Higher levels of these GHGs kept the Earth warm and prevented temperatures from falling to a threshold that would have triggered glaciation.
8,000 years ago, slash and burn societies lit many fires. Today, many forests are being burned in all the jungle sectors and this not only reduces plant cover but it also releases gasses trapped in the leaf litter in swampy areas which, exposed to the sun, dry out and this causes fires to spread even wider when humans burn the upper story off.
Also, hunters of big game discovered they could drive game off cliffs and trap them along rivers if they lit long fires and hunted in large groups. This is probably why few of the large Ice Age mammals survived this latest interglacial. Fires reduce sunlight and can cool off things and if humans did too much burning, it could have changed rain patterns and reduced the warmth. But I doubt this would cool the entire planet nearly insantly as the charts above clearly show.
At the same time as early Americans may have been planting their first squash, hunter-gatherers some 16,000 kilometers east along the banks of the Yangtze River were beginning to cultivate wild rice, according to new studies by archaeobotanist Zhijun Zhao of the Smithsonian Tropical Research Institution and colleagues. Rice, the most important food crop in the world, was long thought to have been cultivated first around 6500 years ago in southern Asia, where the climate is warm enough to support luxuriant stands of wild rice. But in the 1980s, ancient bits of charred rice turned up in a site along the banks of the middle Yangtze River, in the far northern edge of the range of wild rice today. Directly carbon-dated to 8000 years ago, these grains are the oldest known cultivated rice and suggest that the center of rice cultivation was actually farther north.
8,000 years ago, we left the Garden of Eden and became cultivators and herders. This is when we corralled the sheep and began to feed and pet the cats (talk about trans-species conquests!)---um, cats, I should say, decided to colonize humans---heh---it must have been raining a lot and the mice were trying to get into the newly-harvested grains and the cats let the humans know they love warm, dry places and petting. The dogs hung out with the herders and helped move the sheep around and fight off the wolves, tigers, lions and jackals.
Rise of agriculture.
First known marriages in Ancient Near East.
Potatoes and beans are cultivated in South America
Beginning of rice cultivation in East Asia
Domestication of the cat and Bos aegyptiacus ox in Ancient Egypt
Domestication of sheep in Southwest Asia
Huts, hearths, granaries, and nonportable stone tools for grinding grains Africa
Catal Huyuk, men wear animals skins, plus hats of the same material Asia
Houses, kilns, pottery, turquoise carvings, tools made from stone and bone—and most remarkably—bone flutes China
City located in Anatolia, or modern day Turkey where a number of artifacts appear to support evidence for the widespread practice of Goddess worship
All across the planet, many humans living in places that suddenly changed in this brief jerk of temperature change, all began desperately to farm instead of simply walking about, plucking out of nature, things to eat and since farming and protecting harvests, crops and homes is very hard labor, one should assume this was taken up only out of desperation. When things stabilized again 7,000 years ago, I bet many people reverted to the old ways but enough stuck to the agriculture, it grew for the stability of farming means families are stronger as families instead of wandering in the wilderness, they created 'civilization'. And this is the time the Sahara began to dry out and the gentle savanahs turned to howling wastelands except for the great rivers like the Nile and the Euphrates.
But I very seriously doubt humans had a gigantic impact on the world's TEMPERATURES and rainfall! So this bad session of weather 8,000 years ago had another source: Volcanoes.
A volcano avalanche in Sicily 8,000 years ago triggered a devastating tsunami taller than a 10-story building that spread across the entire Mediterranean Sea, slamming into the shores of three continents in only a few hours.
A new computer simulation of the ancient event reveals for the first time the enormity of the catastrophe and its far-reaching effects.
The Mt. Etna avalanche sent 6 cubic miles of rock and sediment tumbling into the water — enough material to cover the entire island of Manhattan in a layer of debris thicker than the Empire State Building is tall.
The mountain of rubble crashed into the water at more than 200 mph. It pummeled the sea bed, transformed thick layers of soft marine sediment into jelly and triggered an underwater mudslide that flowed for hundreds of miles.
There was a major eruption on Versuvius 8,000 years ago. The tsunami certainly had an impact for many humans lived along the shores of the Mediterranean Sea and I fear many were swept aways in this terrible event. Whole islands were cleared along the shores of Greece and the lowlands at the terminus of the Nile as well as the shores of the Middle East were hammered hard.
But this wouldn't change the global climate although the active volcano did add gasses and dust to the stratosphere. This wasn't an ordinary eruption, either, it was pretty powerful. But it wasn't the only volcano to erupt.
Toya Caldera lies in the V-shaped intersection of the Kurile and Japan arcs, along both of which the Pacific plate is subducted northwesterly direction beneath the Eurasian plate at a rate of approximately 10 centimeters per year (Circum-Pacific Map Project, Northwest Quadrant Panel, 1981).
Toya Caldera formed by collapse about 110,000 years B.P., based on the age of pyroclastic deposits that have been related to the caldera-forming event (Ikumura and Sangawa, 1984; Machida and others, 1985; Ikeda and Katsui, 1986). Usu is a truncated stratovolcano with late-stage dacitic domes, located on the southern boundary of Toya Caldera. The main body of Usu was formed by eruptions of basaltic and andesitic magma (Usu somma lava). Then, 7,000 to 8,000 years ago, a violent explosion and a large debris avalanche formed a somma that is now largely filled by dacitic domes. Viscous dacitic magma has on occasion upheaved the land surface by more the 200 meters directly above a cryptodome (for example, Showa-shinzan ("Roof Mountain") in 1943-45).
Most of Toya Caldera is occupied by Lake Toya; the Naka-jima (or Nakano-shima) group of andesitic domes formed an island in the center of Lake Toya before Usu Volcano began to grow. Two additional domes have been identified by bathymetric and magnetic studies of the caldera lake (Nishida, 1984). On the basis of the same magnetic survey, Nishida (1984) proposes that the diameter of the Toya Caldera structure is only half that of the present topographic depression; if so, Usu lies outside the main structure of the caldera, on its modern topographic rim.
Some geological periods see few major volcanic events while others are for some reason, very active. 8.000 years ago was very active. Any event that produces a caldera is a major event. The bigger and deeper the caldera, the more it affects the climate. We know that an eruption 76,000 years ago nearly wiped out humans and the survivors are our ancestors. They had to work hard to survive in very difficult circumstances. On top of this, super-eruptions can cause Ice Ages which are very difficult to survive if one comes from creatures that once lived in jungles, not on ice sheets.
So I kept looking for volcanic events that would force humans to give up their happy-go-lucky ways and end up creating argriculture and herding animals.
Gorely Volcano: A massive shield volcano 1830 m high. Massive andesite lava accumulation in the Early Pleistocene was followed about 33,000 years ago by production of about 120 km3 of ignimbrite accompanied by caldera collapse. Basalts and basaltic andesites then created five volcanoes that coalesced to form most of the modem mountain between 8000 and 6000 years ago; this largely filled the caldera, but sections of the old caldera walls remain visible just outside the shield. Subsequent activity has been on a reduced scale, producing both lavas and tephras; these are exposed in the walls of the summit complex of craters. Recent eruptions have been explosive; in 1981 ash covered an area of 500 km2, and the last eruption was in 1986 when a cloud of steam and ash rose 600 m.
8,000 years ago, the bridge to the New World was broken by the oceans which were rapidly rising and volcanoes along that chain were erupting with violence. The sea water rushing out of the Arctic probably changed the salinity and temperature of the north Pacific. Maybe this triggered volcanic actions because water does interact with volcanic sources to cause steam and then eruptions. Perhaps this unrush of water caused the current flowing around Greenland to change significantly? This could explain why this interglacial is longer than others.
But it doesn't explain the short but brutal cold/dry spell that caused humans in the New World and the Old to both independently develop agriculture at the same time.
Since then the Shastina cone has been built by mostly pyroxene andesite lava flows. Some 9,500 years ago, these flows reached about 6.8 miles (11 km) south and three miles north of the area now occupied by nearby Black Butte (see image at right). The last eruptions formed Shastina's present summit about a hundred years later. But before that, Shastina, along with the then forming Black Butte dacite plug dome complex to the west, created numerous pyroclastic flows that covered 43 mile² (110 km²), including large parts of what is now Mt. Shasta, California and Weed, California. Diller Canyon (400 ft (120 m) deep and quarter-mile (400 m) wide) is an avalanche chute that was probably carved into Shastina's western face by these flows.
The last to form, and the highest cone, the Hotlum Cone, formed about 8,000 years ago. It is named after the Hotlum glacier on its northern face; its longest lava flow, the 500 ft (150 m) thick Military Pass flow, extends 5.5 miles (9 km) down its northwest face. Since the creation of the Hotlum Cone, a dacite dome intruded the cone and now forms the summit. The rock at the 600 ft (180 m) wide summit crater has been extensively hydrothermally altered by sulfurous hot springs and fumaroles there (only a few examples still remain).
This was pretty significant. The American West was rapidly rebounding as the glaciers not only melted but waves of floods poured across the land and rifts opened up and large volumes of lava poured out and obvioiusly, as the North American continent moved relentlessly westwards, the ice sheets could have impeded movement and so this freeing up of stored energy must have led to some pretty amazing earthquakes and we can see, there was a lot of volcanic activity.
But this is in general. There had to be a great event which involved the blowing up a major volcano, an epic event and so there was.
Mount Mazama’s most violent eruption occurred about 7,700 years ago. A column of hot gas and volcanic rock was ejected high into the air. This ejected magma fell to the earth as fragments of frothy white pumice and volcanic ash. Layers of ash from this eruption may still be found in the soil as far away as Alberta, Canada.
Explosions on the northeast side of Mount Mazama produced fast-moving flows of hot ash. In all, 12 cubic miles (50 cubic kilometers) of material poured out of the erupting volcano, draining the magma chamber beneath the mountain. As the underlying support for the mountain was lost, the walls of the volcano began to collapse inward. The top of a mountain that was built over hundreds of thousands of years “disappeared” in perhaps just a few days.
Here is my own candidate. This eruption was huge. It was also on the edge of the retreating Ice Sheets. There was lots of water around. The mountain didn't 'disappear' when it collaped and then blew apart: it went flying into the stratosphere. And the earth was covered by a really thick blanket of fine dust! Temperatures fell dramatically.
And humans had to scratch the earth and protect the plants if they wanted to eat.
This volcano, like the Yellowstone caldera, is still active. There are many candidates for similar blow-ups. These mega-events are around 10,000 years apart which is not reassuring. But then, this is why our planet has evolution and is so full of life: it is, itself, alive. Not frozen in time like the moon, for example.
And so it goes: the dynamic sun that constantly reinvents itself and is relentlessly changing as it ages, the things flying through space that hit us periodically, the oceans, volcanoes, continents moving restlessly, wind patterns, the tilt of the earth, the moon's pulling on everything here and life forms adding and subtracting from it all, a marvelous and hazardous place, this is the earth.