Ice Ages

Introduction: We live in an era where even politicians have realised the significant threat climate change poses to civilization and indeed to all life on Earth, but it is nothing new and has been a major driving force of evolutionary change for hundreds of millions of years. One species that undoubtedly owes its very existence to climate change is Homo sapiens. It is no coincidence that the earliest human species, Homo habilis, emerged at just about the same time as Earth entered an ice age. The subsequent epochs of advancing and retreating ice sheets have played a pivotal role in the evolution and dispersal of subsequent human species, culminating in that of modern humans, Homo sapiens.

The Current Ice Age: We now know that the Earth has been affected by a number of ice ages in its history. The current Ice Age begun 2.6 million years ago and has been characterised by the advance and retreat of major glaciers and ice sheets in glacial periods punctuated by warmer interglacial periods. The last glacial period – or what is popularly known as the last Ice Age – began 110,000 years ago and ended with the onset of the Holocene epoch 11,600 years ago. The Ice Age is not in fact at an end and barring the effects of global warming, the glaciers and ice sheets will one day return.

The origins of the current Ice Age go back some 50 million years. Throughout this time the Earth’s climate has been cooling. Though the reasons are not fully understood, the collision of India with the Eurasian landmass (48-52 million years ago) and the migration of Antarctica to the South Pole (23 million years ago) are thought to be factors. From the first of these two events arose the mountains of the Himalaya Range, uplifted by the collision. The weathering of this new mountain range sequestered CO2 from the atmosphere, leading to global cooling. Subsequently the presence of a large landmass at the South Pole encouraged the build-up of ice. These ice-sheets reflected more of the Sun’s radiation back into space leading, in turn, to further cooling. The tipping point was reached 2.6 million years ago, with the expansion of ice sheets in the Northern Hemisphere.

Discovery: Perhaps surprisingly, the discovery that the northern glaciers had once been far more extensive, reaching as far south as London, New York and Berlin, is comparatively recent. Not until the 19th Century did geologists began to ponder such anomalies as bones of reindeer in the south of France and granite boulders high up on the slopes of the predominantly limestone Jura Mountains. The German-Swiss geologist Jean de Charpentier suspected that the boulders might have been deposited there by glaciers. He discussed the idea with his friend and fellow geologist Louis Agassiz, who took it up with great enthusiasm.

Meanwhile the naturalist Karl Friedrich Schimper, who was also a friend of Agassiz, was also of the opinion that ice sheets had once been far more extensive than now, and had once lain across much of Eurasia and North America. But he was a man who very rarely put his ideas into writing. He did however lend Agassiz his notes, but to his and de Charpentier’s considerable annoyance Agassiz subsequently took all the credit for the theory, which he put forward in a two-volume work entitled Etudes sur les glaciers (Study on Glaciers), published in 1840.

The main problem with the theory as it stood was that it offered no explanation for the cycles between glacial and interglacial periods. That these might have an astronomical cause was first suggested by Scottish scientist James Croll in 1860, who claimed that cyclical changes in the Earth’s orbit around the Sun might be responsible. Croll’s theory attracted considerable interest at the time, but had been more or less abandoned by the end of the 19th Century. The theory was revived and extended in the 1920s and 1930s by a Serbian engineer named Milutin Milanković.

The Milanković Pacemaker: The Earth’s seasons arise from its axis of spin being tilted rather than upright in relation to the plane of its orbit. When either the Northern or the Southern Hemisphere is tilted towards the Sun, it will experience summer as a result of both longer hours of daylight and the Sun being higher in the sky and more of its heat reaching the ground. The other hemisphere, meanwhile, will experience winter. For the Northern Hemisphere, the day with the longest period of daylight or Summer Solstice occurs on 21 June. The day with the shortest period of daylight or Winter Solstice occurs on 21 December. The spring and autumn equinoxes occur when the Earth is mid-way between the solstice positions, and everywhere receives 12 hours of daylight.

At the present time in the Northern Hemisphere, summers are hot enough to melt the whole of the previous winter’s accumulation of snow, but if this was not the case then the latter would gradually build up and ice sheets would advance into temperate latitudes. The enlarged ice sheets would then reflect more of the Sun’s radiation straight back into space, causing the cooling process to accelerate.

Milanković considered the possible effects of astronomical cycles on the intensity of the seasons, the amount of sunlight received (“insolation”) in the Northern Hemisphere and the possibility that at certain times the summers in the Northern Hemisphere might not be hot enough to prevent ice sheets from building up. He took into account three variables now known as the Milanković Cycles: precession of the equinoxes; variation of the axial tilt (“obliquity”) and changes in the shape of the Earth’s orbit around the Sun (“eccentricity”).

Precession is the long-term oscillation experienced by the Earth in which the spatial orientation of the axis changes with time. The phenomenon may be likened to the wobbling of a spinning-top or a gyroscope and is caused by caused by tidal effects of the Moon and Sun. A complete cycle takes 25,800 years. Precession affects the time of the year when the Earth is at is closest to the Sun (“perihelion”), which in turn will affect the intensity of the seasons. The picture is complicated by the precession of the orbit itself, with the perihelion slowly migrating around the Sun in a 105,000 year cycle. If these are combined with cyclical changes in the shape of the Earth’s orbit, a periodicity of 21,700 years is obtained for perihelion coinciding with summer in each hemisphere.

The Earth’s axial tilt is currently 23.5 degrees, but varies between 21.8 and 24.4 degrees over a period of 41,000 years. The seasons for both hemispheres will be exaggerated when the angle of tilt is high and moderated when it is low.

Finally the Earth’s orbit changes from near-circular (“low eccentricity”) to an ellipse (“high eccentricity”) with a major cycle of 400,000 years and a number of smaller cycles that average out at 100,000 years. At times of high eccentricity, the seasons are exaggerated in the hemisphere experiencing summer close to perihelion, and moderated in the other.

How these differing cycles combine to either exaggerate or moderate the seasons is of course very complicated, and Milanković spent many years laboriously performing the relevant calculations which – in an era before computers – all had to be carried out with the aid of a slide rule and books of tables. Unfortunately his dates for glacial periods did not tally with the then accepted values, and his theory fell out of favour. However in the late 1960s and early 1970s advances in methods for dating proxy evidence (indications of glacial periods) vindicated Milanković’s predictions and his theory gained widespread acceptance.

Although the duration of glacial periods is now seen to correspond closely to expectations, different cycles seem to have dominated at different times. Prior to 800,000 years ago, glacial periods followed the 41,000 year obliquity cycle, but subsequently the 100,000 year orbital eccentricity cycle has been dominant.

Effect upon Sea Levels: During glacial periods, significant amounts of water are locked up in ice sheets and sea levels fall. At the time of the Last Glacial Maximum (LGM), when the ice sheets reached their maximum extent, 20,000 years ago, sea levels were roughly 120 metres below their present-day level. Britain and Ireland were joined to continental Europe and the Indonesian islands as far east as Borneo and Bali were joined to mainland Asia as part of a subcontinental landmass known as Sundaland. Australia was connected to New Guinea and Tasmania and though it remained separate from Sundaland, the gap was small and could be crossed by humans living at that time.

Effect upon Climate: During the LGM, the climate throughout the world was cooler and dryer. The arid conditions were a consequence of so much water being locked up in ice sheets. In some parts of the world such as Southern Australia and the Sahel Belt south of the Sahara, rainfall dropped by up to 90 percent. Throughout the world deserts expanded and rainforest shrank.

During interglacial periods, the climate is warmer and wetter. In Africa, a weather phenomenon known as in Inter-Tropical Convergence Zone (ITCZ), which normally brings monsoons to the tropics, can extend its influence northwards. During such epochs, the Sahara experiences moist wet conditions and savannah climate. The last such climatic optimum was the Holocene Thermal Optimum, which began at the end of the last glacial period and peaked around 4000 BC. Subsequently, Milanković-determined insolation declined, the ITCZ returned southwards and the Sahara rapidly dried up.

References:

Bryson, B. (2003) A Short History of Nearly Everything, Doubleday.
Evans, E.P. (1887) The North American review, Volume 145, Issue 368, July 1887.
Klein, R. (1999) The Human Career (2nd Edition), University of Chicago Press.
Wilson, R.C.L., Drury S.A. and Chapman J.L. (2000) The Great Ice Age, Routledge.

© Christopher Seddon 2008

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Hagopian’s Ark

In 1970, a 70-year-old Armenian businessman named George Hagopian created headline news across the world by claiming that as a boy, he had visited Noah’s Ark on Mount Ararat twice with his uncle, in 1908 and 1910.

Hagopian was from Van, a city located on the eastern shore of Lake Van in what is now eastern Turkey. His grandfather was minister of the Armenian Orthodox church there and frequently told young George stories about the “holy ship” on the “holy mountain”. Mount Ararat is sacred to the Armenians, whose traditions hold they were the first race of humans to appear after the Flood. It has featured on the Armenian national coat of arms since Soviet times, much to the annoyance of the Turks, who protested that it was part of their territory (the Soviets retorted that the crescent on the Turkish flag surely didn’t mean that the Turks laid claim to the Moon).

Mount Ararat is an extinct volcano located in eastern Turkey, overlooking the borders with Armenia and Iran. It is what is known as a stratovolcano – formed from lava and pyroclastic flow. Although its dating is uncertain, it probably forming as a result of vulcanism arising when the Tethys Sea closed, 15 million years ago.

Its northern and eastern slopes rise from the broad alluvial plain of the Aras River, about 3,300 ft (1,000 m) above sea level; its southwestern slopes rise from a plain about 5,000 ft above sea level; and on the west a low pass separates it from a long range of other volcanic ridges extending westward toward the eastern Taurus ranges. The Ararat Massif is about 25 miles (40 km) in diameter. It comprises two peaks, about seven miles apart, known respectively as Great Ararat and Little Ararat. Great Ararat rises 16,854 feet above sea level, and is the highest peak in Turkey; Little Ararat rises to 12,782 feet.

High above the Aras plain the Armenians built a monastery to commemorate St. Jacob, who is said to have tried repeatedly but failed to reach the summit of Great Ararat in search of the Ark. The monastery was destroyed by an earthquake and avalanche in 1840.

Hagopian’s uncle had been forced by a four-year drought to move from Van to a village at the foot of Ararat in search of better grazing for his sheep and young George was staying with him when one day the two of them climbed Mount Ararat in search of the Ark. They believed that the drought conditions might have melted the snow and ice that usually covered it.

On the way, they passed Ahora Gorge and the remains of St. Jacob’s monastery. As the mountain became steeper, Hagopian’s uncle carried the boy on his shoulders. At length, close to the summit, they came to something resembling a giant barge, perched on a rocky ledge and partially covered in snow. At first Hagopian thought it was a stone house, but his uncle showed him the outline of planks, and he realised it was the Ark “just like the other people had described it to him”. His uncle lifted him on to the Ark roof, telling him not to be afraid because “it is a holy ship… the animal and people are not here now. They have all gone away.” Hagopian kissed the surface of the roof, but his uncle rather irreverently fired a gun at the Ark’s hull. The bullets bounced off. He then tried to cut off a piece of wood, but without success.

After two hours, during which they looked at the Ark and ate some food, the pair returned to their village, where Hagopian related his adventure to other boys of his age, only to receive the dismissive reply, “yes, we saw the Ark too”.

Hagopian claimed to have made a second visit two years later, but by that time the Ark was largely buried in snow.

Hagopian was unable to pinpoint his journey on a map, though he claimed that if he could get back on to the mountain he could lead investigators to the Ark. Unfortunately Mount Ararat is sited at what had by that time become one of the most sensitive locations on Earth, right on the border between Turkey and the Soviet Union, and in the middle of activities by Kurdish separatists. Hagopian died in 1972 without getting the chance to lead investigators to the site.

The search for Noah’s Ark has a long history, and expeditions to Mount Ararat for that purpose have been conducted since the early 19th Century. Although there have been many claimed sightings, none are wholly convincing. Ark searchers point to the “Ararat anomaly” – an object near the summit of the mountain that appears on Cold War-era photographs taken from aircraft and spy satellites – but to be candid, these are about as convincing as the so-called Face of Mars, so popular with conspiracy theorists. It seems very strange that well-equipped expeditions and aircraft cannot locate a site reached without undue difficulty by a man and a young boy, and apparently known to many other villagers.

Logically there are only three possibilities: firstly Hagopian was lying and made the whole thing up; secondly he was telling the truth and actually did see the Ark with his uncle; thirdly he genuinely believed he had seen the Ark in his childhood, but was mistaken.

Hagopian underwent lie-detector tests, which suggested that he was telling the truth. Admittedly these tests are notoriously unreliable; and in addition Hagopian was questioned by people who clearly wanted to believe him. It has also been pointed out that in old age Hagopian had no living relatives and few friends; he may have been seeking attention. However he was known by business associates as an honest man, and let us suppose for the sake of argument that he was not lying.

Could he, therefore, have actually seen the Ark? The world-wide prevalence of flood mythology leaves little doubt that these stories do relate to real events. At the end of and in the wake of the last ice age, sea levels rose dramatically around the world. Great Britain and Ireland became separated from Europe; according to one theory the Black Sea was created by a flood occurring around 5600 BC when the Mediterranean broke through the Bosporus; further east the Sunda Peninsula disappeared, leaving only the islands of Sumatra, Java and Borneo above water. It seems highly likely that the origin of the flood mythology is tribal memories of these events, possibly conflated with accounts of more recent and more localised floods.

However this is a far cry from all the landmasses of the Earth being submerged to a depth of in excess of 16,854 feet (the height of Great Ararat): the idea is absurd. Where could all that water have come from and, no less important, where did it go?

Even if we allow some freak condition such as a tsunami to have stranded a ship near the summit of Ararat, we run into the question as to whether a vessel the size of the Ark could have been constructed in late prehistoric times, the presumptive time of the Flood, using Bronze Age technology.

It is entirely possible that Noah’s Ark existed – a watercraft built to carry animals and other goods for trade. Caught up in a flood, it enabled it crew and cargo of animals to survive until the floodwaters receded. However, the Ark is supposed to have been 300 cubits in length – about 450 feet or 135 metres. That is about the size of a present-day cross-channel ferry. For comparison, Nelson’s flagship HMS Victory measures 227 feet, Brunel’s SS Great Britain is 322 feet and the Titanic was 882 feet. The earliest ship to significantly exceed the Ark’s reputed dimensions was Brunel’s SS Great Eastern, a 690 foot leviathan launched in 1858 – after four years in the building, and pushing the envelope of Victorian technology to the very limit. While the achievements of Bronze Age people are impressive – the Pyramids are an obvious example of what they were capable of – it seems unlikely in the extreme that they would have been capable of constructing a vessel of such size – especially in a short space of time. Bear in mind too that armies of slaves were required to build the Pyramids, and even so they required many years of toil to complete.

I feel it is absolutely certain that there is not, and never has been, a 450-foot Bronze Age ship resting close to the summit of Mount Ararat. It is just as likely that the Ark was built with the assistance of one of Erich von Daniken’s alien astronauts.

So if Hagopian was not lying, and he did not see the Ark, then just what did he see? One thing that stands out to me is that the account has a disjointed, dreamlike quality to it. Hagopian initially thinks he is seeing a rock formation, but then his uncle points out the outline of planks. Crucially he has previously had the Ark described to him: only now does he see it just as he was told it would be. His uncle’s behaviour is strange: he speaks of the Ark as a “holy ship”; but then he fires a gun at it and tries to hack off a piece of it with a knife. And what is he doing with a gun in the first place? Finally Hagopian is telling other boys about the Ark, but they reply that they’ve already seen it. If the Ark was so widely known among the villagers, wouldn’t somebody have mentioned it sooner?

I think Hagopian is describing a dream – a dream so vivid he later confused it with reality.

Here is what I believe actually happened:

1.Hagopian learns about the Ark from his grandfather and – like many a boy of that age, develops an obsessive interest (at his age I was obsessively interested in ships and aeroplanes).

2.He goes to stay with his uncle and begs him to take him up the mountain in search of the Ark.

3.To humour the lad, Hagopian’s uncle eventually does take him up the mountain. They see, close to the summit, a rocky outcrop, largely covered by snow. Possibly they see the Ararat Anomaly. Hagopian’s uncle is probably by now keen to end the jaunt and never intended to go so high. He tells the boy that it is the Ark. Hagopian isn’t convinced.

4.This is in fact the only time they ascend the mountain, but in later life Hagopian recalls it as his second visit to the Ark.

5.The account of Hagopian’s first visit to the Ark is actually a vivid dream, occurring shortly after the expedition.

6.The dream recurs in Hagopian’s later life, to the extent that he eventually becomes convinced that he actually did visit the Ark as a young boy.

Many a time he would have awoken from his dream. In the fleeting moments that followed wakening, he would be convinced he knew the location of the Ark, and that he could return there. At first, the dream would fade next day – but in time as he grew old he was unable to distinguish between reality and the first occurrence of the dream.

Inevitably Bible literalists seized on Hagopian’s claims to have seen the Ark, and to this day they can be read on countless creationist websites. Most versions seem to have been simply cut-and-pasted from Bermuda Triangle enthusiast Charles Berlitz’s 1987 book “The Lost Ship of Noah”.

© Christopher Seddon 2008