Supercontinent: Ten Billion Years in the Life of Our Planet (14 page)

As Pangaea has moved steadily north through the Permian, the South Pole has all but slipped into the sea. The great continental icecap that had existed for many millions of years since the Carboniferous has finally melted away completely, releasing the last of its cargo of mud and boulders the size of men. Unique to Gondwanaland, dense forests of
Glossopteris
trees, standing up to twenty-four metres tall, the shape of Christmas pines and growing a thousand to the acre, fringe the southern coasts of Tethys and stretch inland to within twenty degrees of the pole.

These forests of the polar night withstand two seasons: one of feeble light and one of unremitting dark. Today’s world has no
equivalent
of this eerie ecosystem. Their growth rings show that each summer these trees grow frenetically. Those nearer the coast are lashed by megamonsoon rains roaring in from Tethys, the thick cloud further weakening the feeble sunshine raking the latitudes at the bottom of the world. And as the brief growing season comes to an end, and the orbital progress of the leaning Earth draws the sun in its undulating course daily closer to the horizon, the tongue-like leaves turn wild and fall on thick beds of countless others on the sodden forest floor. The sun dips further, finally no longer peeping above the ending line, and all growth ceases for six months without prospect of a dawn.

Leaves that will one day lie fossilized beside the frozen body of Captain Scott fall into the anoxic peat. The great Permian coals store up the Sun’s ancient energy like a battery, waiting for release in power stations and steel mills.

These coal-producing forests occupy a climate zone designated ‘tropical everwet’ and, according to the occurrence of coals at this time, this zone extended from about midway along the southern coast of Tethys, across the island archipelagoes standing in the great gulf’s mouth, to the northern shore’s eastern promontory, and then back west, ending not far short of where the Ural mountains join the coastal cordillera. Oil source rocks and coral reefs cluster here,
bearing
testimony to the high organic productivity of the Permian tropics.

Around the reef-fringed Tethys, only rarely does this everwet zone give ground, and then mostly to ‘tropical summerwet’ conditions that also prevail across the mountainous mid-section of equatorial Pangaea and extend only a little way east along each shore of the great embayment.

Tropical summerwet is too dry for coals, and none is found today in places that were once situated here. But coal can, and does, form beyond the everwet tropics. It is a common misconception that all coal forms in steaming swamps like the Amazon or Congo basins of today. The main requirement for coal formation is a high water table that prevents plant matter from decaying. So, if that can be combined with high productivity of plant matter, coals can also form in cool and warm-temperate climate zones. This was particularly true over Gondwanaland, clothed with its unique
Glossopteris
forests, growing amid the lakes and valleys of the sodden, recently deglaciated
southern
continent. But plant remains (not abundant enough to make coals, though significant enough to create tantalizing ‘floral
localities
’) also extend around the shallow seas running south from the northern Boreal Ocean – like the Zechstein.

Despite these exceptions the main signature of Pangaea is one of almost unremitting aridity. The continent is too large for the moisture of the oceans to reach its interior; the late-Permian atmosphere, richer in carbon dioxide by perhaps five times the modern level, holds in the heat of the weaker Sun. In the parched heart of the northern and southern lobes of Pangaea summer temperatures soar over 45°C, while at polar latitudes they fall in winter below –30°C. South of the equatorial mountains, salt flats, gypsum playas and dune fields link the west coast of Pangaea, across the whole of the landmass that is now split into North America, North Africa and Arabia, to the
southern
shore of Tethys. North of it, desert; from shining, reef-fringed western shores bordering Panthalassa, all the way to the towering Urals – interrupted only by ephemeral, evaporating seas, recently filled and soon to teem with rich, spiny shellfish adapted to their bitter, hypersaline waters.

Further north, around the Boreal Ocean and its embayments, under the northerly storm track, the prevailing westerlies bring
moisture in from Panthalassa, just as they do today from the Pacific to the boreal rainforests of moss-curtained pinestands of Washington State and British Columbia. But that moisture is soon spent and cannot penetrate far inland, so these conditions give way rapidly
eastward
to cool and finally cold temperate zones along the chilly, but ice-free, roof of the end-Permian world; a silent tundra shore, where soon some of the largest volcanic eruptions in Earth history will
devastate
hundreds of thousands of square kilometres, burying them in kilometres-thick lava piles and nearly bringing the whole story to an end, even before the first dinosaur stalked the planet.

Since Alfred Wegener first pieced it back together in 1912, Pangaea continues to be reborn in the minds of Earth scientists – and their computers – as a living and ( just about) breathing world; a unique place with many lessons to teach us about how our planet’s climate works. It is the supercontinent about which we will always know most, because it is not long gone; its sediments are everywhere; our modern oceans contain a magnetic road map that helps us reconstruct it from its shattered remnants. Pangaea gave us much of our coal; Tethys laid down most of our oil and gas; evaporites formed in its shelf seas gave us nearly all our salt, on which almost all our chemical industries were established. The Zechstein Sea even gave us the fabric of the Palace of Westminster, and the treacherous landscape of Ripon. It even gave us dinosaurs, Alice and the rabbit hole.

Pangaea was the first lost supercontinent that actually
existed
to be imagined by the human mind. In one sense, it is still and always will be a fantasy; but one constrained by uniformitarianism – not Lyellian, but one that truly takes full account of the importance of the rare event in geological time. Thus the human imagination is held within
the fruitful confines of method. You can see the effect of this in every academic reconstruction of Pangaea. Ever since Wegener himself, whose didactic purpose made them necessary, the outlines of the
present
continents are always made clear, embodying the claim of this supercontinent to its objective reality.

But what of older supercontinents? What of the supercontinent that broke up to give us Pangaea? And the one before that? Compared with Pangaea, those lost worlds seem truly lost. As with all
geological
evidence, the older it is, the less of it survives, the more mangled it has become and the harder it is to interpret. It is all but impossible to picture them – to see oneself standing on them – as you can with Pangaea. They have their magical names, which lend them reality of a sort despite the fact that, for some, even their very existence remains controversial. About Rodinia, Pannotia, Columbia, Atlantica, Nena, Arctica or distant Ur, the mists of time gather ever more thickly.

A white-backed vulture, circling high over the empty central deserts of Namibia one day in 1940 would have seen something odd going on at the bottom of one of the rocky gorges of the Kuiseb River, which drains the Khomas Hochland west of Windhoek. Unusually for a Namibian river, the Kuiseb does not peter out into the Namib Desert but runs into the South Atlantic at Walvis Bay, the major port along Namibia’s beautiful but forbidding Atlantic coastline.

There has been a river valley at Kuiseb for perhaps thirty million years, though the present gorge is as little as two million years old, dating from the beginning of the last Ice Age, when global sea levels fell dramatically. Today, for most of the time, there is no water in the Kuiseb River, but the size of some boulders, the smoothing of the rocks high along its banks, or the occasional telltale tangle of logs and brushwood, lodged way up in the cliff, speak of the river’s terrible
force when rains finally come to Khomas Hochland. Yet, luckily for the game, and the occasional bushman trekking by, water often
persists
in isolated pools on the valley floor, even through the dry intervening months and years.

At any time such water holes might play host to a troupe of zebra, encircled by a cloud of hoof-kicked dust; or to a lone gemsbok, his dark, ribbed horns sweeping upright as he dips his head to drink in the still heat. Light-coloured tracks lead off from the pool in all
directions
. All around the water the trampled dust lies like buff flour. There is no patch that does not bear a hoof print. An animal reek, from the spoor and urine with which the visiting beasts pollute their source, hangs in the air. But on that day in the first year of the Second World War, the hole has human visitors.

Two naked young German geologists are wading through its tepid, greenish water, catching carp with a makeshift fence-net made out of two bed sheets sewn together with a pair of string underpants and stiffened with tamarisk twigs. One of these intrepid hunters is Dr Hermann Korn; the other – owner of the sacrificed pants – Dr Henno Martin. Both are on the run.

The two fugitives, who had both studied in the ancient University of Göttingen in Germany, had rejected the rise of fascism in their own country and emigrated to the protectorate of South West Africa, a former German colony. They earned their living on water exploration projects and together got to know the geology of this remote country. But not remote enough; before the growing tide of war, the two men, fearing internment by the South African Mandatory Government, hatched a plan. They would escape, to live a Robinson Crusoe existence in the desert they had come to love; and on 25 May 1940, with a stolen truck full of essential provisions, their dachshund Otto, an air rifle, a pistol and some ammunition, they set off for the wilderness.

Their desert sojourn, a constant battle for survival fought over
water, food and the many dangers of the desert and isolation, lasted two years. It was described in a book known in English as
The Sheltering Desert,
which Martin wrote for his wife and published in 1956, ten years after Hermann Korn was killed in a road accident.

Martin and Korn were not on the run for their lives. In the desert their lives were in just as much danger as they would have been in an internment camp. Yet – and Martin’s book does not make this clear, perhaps because it would have been too painful a thing to say in post-war Germany – the prospect of internment was not made so appalling by the fact of imprisonment alone, or even fear of the regime in whatever camp might have received them. It was fear of their fellow internees, who would most likely have been ardent Nazis.

Forsaking the hideous regime in their native Germany for the
freedom
of the southern African desert in the late 1930s, Martin and Korn found themselves in one of the bastions of free tectonic thought and quickly became aligned with it. Here, where geological evidence for the break-up of Gondwanaland was at its most stark and
undeniable
, Wegener already had his greatest champion. In the heart of Suess’s old imagined domain, amid the reality of evidence that the great London-born Austrian had first pieced together from books in Vienna, Henno Martin and Hermann Korn found themselves
walking
in the footsteps of one of the greatest field geologists of all time: Alexander du Toit.

In 1961, just as the tide was beginning to turn for Wegener’s theory, Henno Martin delivered a memorial lecture to Alex du Toit at the Geological Society of South Africa, appropriately entitled ‘The hypothesis of continental drift in the light of recent advances of
geological
knowledge in Brazil and south west Africa’. The paper was a development of Namibia-based work he and Korn had carried out (partly during their desert exile) and published in the decades before;
gathering detailed evidence of the ancient glaciation in that
geologically
unknown region, and fitting it together with the patterns of glacier movement first assembled by Suess and later taken up by Wegener in his reconstruction of Pangaea.

Martin’s later work in Brazil, which sought to make the
correlations
between sequences now separated by the South Atlantic more precise and therefore persuasive, followed pioneering work in the same vein by du Toit. South Africa’s greatest geologist, a man decent and truthful to the roots of his hair, came in 1924 to be on another continent pretending to the Carnegie Institution of Washington, which was paying his expenses, that he had nothing more on his mind than the simple collection of data whereas in fact he was looking for evidence to prove a rogue theory that most geologists (and especially geophysicists) in the USA ridiculed.

Alexander Logie du Toit was born in 1878 at Klein Schuur, under the shadow of Devil’s Peak and Table Mountain, in the Colony of the Cape of Good Hope. His protestant family, which originated around Lille in northern France, began its journey to South Africa from the Netherlands, where it had been driven by religious persecution. From there in 1687, two brothers du Toit sailed for the Cape, establishing their family dynasty one year ahead of the main body of Huguenot settlers, who contributed so much (include wine-making expertise) to South Africa. Du Toit eventually became one of the most widespread family names among the province’s settlers.

The other element in du Toit’s genetics was Scottish. Shortly after the British took over the Cape, Alexander Logie, a naval captain from Fochabers, Inverness, married into the family and took over the estate at Klein Schuur. Scots genes, however, had a little more difficulty
gaining entry. Alexander, having no children of his own, adopted his wife’s nephew (also called Alexander Logie du Toit) as his son and heir. He eventually came to marry
his
cousin, Anna Logie. Their union produced four children, the eldest destined to become South Africa’s first and greatest home-grown geologist.

Du Toit graduated from the forerunner of the University of Cape Town and then attended the Royal Technical College in Glasgow, where, in 1899, he qualified in Mining Engineering. After two years studying at London’s Royal College of Science, he was invited back to Glasgow, where he held two posts, as lecturer in Mining Engineering at the Royal Technical College and in Geology at Glasgow University. Then, in 1903, du Toit sailed back to the Cape to join its new Geological Commission, charged since 1895 with
geological
surveys and mapping in the resource-rich colony.

In the years between beginning work in 1903 and leaving the Survey in 1920, he mapped in detail over 50,000 square miles between the Cape and Natal. Of this enormous area, nearly 43,000 square miles found its way into published geological maps. Much of his work was carried out from a donkey wagon, his mobile home kept by his diligent and long-suffering Scottish wife. From this vehicle he would venture out across trackless mountain and veldt
on a bicycle
. And that is not all. Geological mapping depends on having a base topographic map – or today an aerial or satellite picture – on which the geologist plots his rock types and readings of technical measurements. Nothing useful can be done without one. However, for much of the area du Toit mapped, there were no such maps. So he made them too, using a small plane table (a level sighting and drawing surface mounted on a tripod) that he would carry with him on his bike. In effect he mapped much of this vast area twice.

There is always a tendency to beatify the departed in their
obituaries
, but reports of du Toit’s character are too consistent for this to
be the case with him. For all his stature and eventual fame among fellow geologists, du Toit was innately modest, eternally wary of
limelight
, kind and generous with people he met, in whom he clearly took a warm and sympathetic interest whatever their status. Reports abound of his phenomenal powers of recall, he not only wrote
everything
down but remembered where he wrote it down. Yet, as with Suess, his attention to detail was matched by an equal flair for the grand vision. He was also an unstinting worker, whose superhuman capacity for physical and mental effort continued almost unabated right up until his death, from a cancer diagnosed two years before but which he bore in silence and in secret.

One would think that he must have been an impossibly saintly man, were it not for the sly twinkle in so many of his portraits and an ingrained liking for devilment, for upsetting the applecart. The first inkling of this trait would come from his air of faintly amused
detachment
, his quaint and subtle sense of humour and certain unexpected pleasures. He had an unnerving tendency in company to spring up suddenly and recite questionable limericks. His musicality extended to a lifelong love of playing the oboe; and at one stage this outwardly quiet and unassuming intellectual took up motorcycle racing. He cut a strange figure for a rebel, but rebel he was.

If anyone needed an example of how a theory’s acceptance could have benefited from a bit of simple PR, then Alfred Wegener’s book
On the Origin of Continents and Oceans
provides it. The truth is that Wegener could not have done more to antagonize scientists in the USA if he had tried.

Derek Ager was able to write in 1961 that while he himself was (then) in a minority among British geologists in opposing drift,
‘American geologists appear to regard the Declaration of Independence as retroactive to the Palaeozoic.’ The hypothesis of continental drift was nowhere more despised and rejected than in the United States, and by the late 1950s it set the ‘island continent’ apart from the rest of the scientific world. This division today seems all the more remarkable because now you might be forgiven for thinking it was American geophysicists who invented it. The truth of how this schism came about is an object lesson in the influence of prevailing culture upon science; and how it was eventually healed, as the great supercontinent of science reunited around a new paradigm,
demonstrates
the self-correcting nature of the scientific endeavour.

Objectivity in science is a contentious and difficult issue. At its heart lies a basic question: how should a scientist approach nature? To take two extremes: one, you go to nature and record what you observe. You clear your mind of any explanatory theories and amass data. But factual data on their own do not explain anything, so after all this observational effort you allow explanations to
emerge
. This is called the inductive method. Alternatively, you can first develop a theory – a hypothesis – about how you think nature works, and then go out to test that theory by observation. This is called the deductive method, or sometimes the hypothetico-deductive method.

At their extremes these two approaches produce, in one case, colourless fact-gathering, and in the other, an unhealthy dominance of ruling theory that blinds the observer to observations that don’t fit. Clearly, the way in which science
really
works is a sensible and
pragmatic
mixture of the two; but balancing them has always been fraught with difficulty, not least in geology.

Many early geological thinkers in the eighteenth century had deductive tendencies. They imagined all-embracing ‘theories of the Earth’, expounded in thick tomes that offered ideological frameworks of how the Earth evolved into its present state. By the time the
Geological Society of London was founded in 1807, after the
spectacular
failure of several such ruling theories, advanced thought had swung back towards the inductive method. The general mood of the time was that science needed more facts. The stirrings of an ‘Anglo-Saxon’ approach to science were beginning to make themselves felt. The great early theorists of the Earth had been chiefly French and German. And while the Scots geologist James Hutton (1726–97), originator of uniformitarianism, also called his great book
Theory of the Earth,
his approach was truly more aligned with the observers than the grand theorizers.

Not that Hutton lacked grand theory. It was his concept of
judging
the record of the past by extrapolating from the present that Charles Lyell developed into its extreme form in the nineteenth
century
; and thus gave the whole tenor of the research conducted and published by the Geological Society of London its objective, inductive cast. This was very much in opposition to the caricature of
continental
science as over-theoretical and dogmatic, driven by God-like professors with their ruling theories and personal authority. This
caricature
, like all good caricatures, has some basis in truth, and is reflected in the German term
Weltall
that is given to this kind of theory and which means ‘whole world’.