The dialectics of geology
There is an English saying, “as solid as the ground under our feet.” This comforting idea, however, is very far from the truth. The earth beneath our feet is not as solid as it seems. The rocks, the mountain ranges, the continents themselves, are in a continuous state of movement and change, the exact nature of which has only begun to be understood in the latter half of this century. Geology is the science that deals with the observation and explanation of all the phenomena that take place on and within the planet. Unlike other natural sciences such as physics and chemistry, geology bases itself, not on experiments, but on observation. As a result its development was heavily influenced by the way in which these observations were interpreted. These, in turn, were conditioned by the philosophical and religious trends of the day. This fact explains the tardy development of geology in relation to other earth sciences. Not until 1830 did Charles Lyell (1797-1895), one of the fathers of modern geology, show that the earth is far older than the book of Genesis says. Later measurements based on radioactive decay confirmed this, establishing that the earth and the moon are approximately 4.6 billion years old.
From the earliest period, men and women were aware of phenomena like earthquakes and volcanic eruptions that revealed the tremendous forces lying pent up beneath the earth's surface. But until the present century such phenomena were attributed to the intervention of the gods. Poseidon-Neptune was the “earth-shaker”, while Vulcan-Hephistes, the lame blacksmith of the gods, lived in the bowels of the earth, and caused volcanoes to erupt with his hammer-blows. The early geologists of the 18th and 19th centuries were aristocrats and clergymen, who believed, with Bishop Ussher, that the world had been created by God on 23rd October 4004 B.C. In order to explain the irregularities of the earth's surface, such as canyons and high mountains, they developed a theory—catastrophism—which tried to make the observed facts fit in with the Biblical stories of cataclysms, like the Flood. Each catastrophe wiped out whole species, thus conveniently explaining the existence of the fossils which they found buried deep inside the rocks in coal mines.
It is no coincidence that the catastrophe theory of geology gained most ground in France, where the Great Revolution of 1789-94 had a decisive influence on the psychology of all classes, the echoes of which reverberated down the generations. For those inclined to forget, the revolutions of 1830, 1848, and 1870 provided a vivid reminder of Marx's penetrating observation that France was a country where the class struggle is always fought to the finish. For Georges Cuvier, the celebrated French naturalist and geologist of the 19th century, the earth's development is marked by:
“a succession of brief periods of intense change and that each period marks a turning point in history. In between, there are long uneventful periods of stability. Like the French Revolution, after upheaval, everything is different. Likewise, geographical time is subdivided into distinct chapters, each with its own basic theme.” 1
If France is the classical country of revolution and counter-revolution, England is the classical home of reformist gradualism. The English bourgeois revolution was, like the French, quite a bloody affair, in which a king lost his head, along with a lot of other people. The “respectable classes” in England have been trying hard to live this down ever since. They far prefer to dwell on the comically misnamed “Glorious Revolution” of 1688, an inglorious coup d'état in which a Dutch adventurer acted as the middleman in an unprincipled carve-up of power between the money-grubbing nouveaux riches of the City and the aristocrats. This has provided the theoretical basis for the Anglo-Saxon tradition of gradualism and “compromises”.
Aversion to revolutionary change in any shape or form is translated into an obsessive concern to eliminate all traces of sudden leaps in nature and society. Lyell put forward a diametrically opposite view to catastrophism. According to him, the boundary line between different geological layers represented not catastrophes but simply recorded the shifting pattern of transitions between two neighbouring sedentary environments. There was no need to look for global patterns. Geological periods were merely a convenient method of classification, rather like the divisions of English history according to reigning monarchs.
Engels paid tribute to Lyell's contribution to the science of geology:
“Lyell first brought sense into geology by substituting for the sudden revolutions due to the moods of the Creator the gradual effects of a slow transformation of the earth.” However, he also recognises his deficiencies: “The defect of Lyell's view—at least in its first form—lay in conceiving the forces at work on the earth as constant, both in quality and quantity. The cooling of the earth does not exist for him; the earth does not develop in a definite direction but merely changes in an inconsequent fortuitous manner.” 2
“These views,” writes Peter Westbroek, “represent the dominant philosophies of the nature of geological history—on the one hand catastrophism, the notion of stability interrupted by brief periods of rapid change, and on the other, gradualism, the idea of continuous fluctuation. In Coquand's time, catastrophism was generally accepted in France, but sympathy for this philosophy would soon fade, for purely practical reasons. Geological theory had to be built from scratch. The founders of geology were forced to apply the principle of the present as the key to the past as rigorously as possible. Catastrophism was of little use precisely because it claimed that the geological conditions were fundamentally different from those in the subsequent periods of stability. With the far more advanced geological theory now at our disposal, we can adopt a more flexible attitude. Interestingly, catastrophism is regaining momentum.” 3
The argument between gradualism and catastrophism is really an artificial one. Hegel already dealt with this by inventing the nodal line of measurement, in which the slow accumulation of quantitative changes gives rise to periodic qualitative leaps. Gradualism is interrupted, until a new equilibrium is restored, but at a higher level than before. The process of geological change corresponds exactly to Hegel's model, and this has now been conclusively proved.
At the beginning of the 20th century, Alfred Wegener, a German scientist, was struck by the similarity of the coastlines of eastern South America and the West Coast of Africa. In 1915, he published his theory of the transposition of continents, which was based on the assumption that, sometime in the past, all the continents had been part of a single great landmass ( Pangaea), which later broke up into separate landmasses which drifted apart, eventually forming the present continents. Wegener's theory inevitably failed to give a scientific explanation of the mechanism behind continental drift. Nevertheless, it constituted a veritable revolution in geology. Yet it was indignantly rejected by the conservative geological community. The geologist Chester Longwell even went so far as to say that the fact that the continents fitted together so well was “a trick of the devil” to deceive us. For the next 60 years, the development of geology was hampered by the dominant theory of “isostacy”, a steady state theory that only accepted vertical movements of the continents. Even on the basis of this false hypothesis major steps forward were made, preparing the ground for the negation of the theory that increasingly entered into conflict with the observed results.
As so often happens in the history of science, technological advance linked to the requirements of production, provided the necessary stimulus for the development of ideas. The search for oil by big companies like Exxon led to major innovations for the investigation of the geology of the seabed, and the development of powerful new methods of seismic profiling, deep-sea drilling and improved methods for dating fossils. In the mid-1960s, Peter Vail, a scientist in Exxon's main Houston laboratory, began to study the irregularities in the linear patterns on the ocean floor. Vail was sympathetic to the old French view of interrupted evolution, and believed that these breaks in the process represented major geological turning points. His observations revealed patterns of sedimentary change that seemed to be the same all over the world. This was powerful evidence in favour of a dialectical interpretation of the geological process.
Vail's hypothesis was greeted with scepticism by colleagues. Jan van Hinte, another of Exxon's scientists, recalled: “We palaeontologists didn't believe a word he was saying. We were all brought up in the Anglo-Saxon tradition of gradual change, and this smelled of catastrophism.” However, Jan van Hinte's own observations of the fossil and seismic record in the Mediterranean, revealed exactly the same as Vail's, and the ages of the rock corresponded to Vail's predictions. The picture that now emerges is clearly dialectical:
“It is a common feature in nature: the drop that makes the bucket overflow. A system that is internally stabilised is gradually undermined by some external influence until it collapses. A small impetus then leads to dramatic change, and an entirely new situation is created. When the sea level is rising, the sediments build up gradually on the continental shelf. When the sea goes down, the sequence becomes destabilised. It hangs on for some time, and then—Wham! Part of it slides into the deep sea. Eventually, sea levels begin to rise and bit by bit, the sediment builds up.” 4
Quantity changed into quality when in the late 1960s, as a result of deep-sea drilling on the ocean floor, it was discovered that the seabed of the Atlantic Ocean was moving apart. The “Mid-Ocean Ridge” (that is, an under-sea mountain chain located in the Atlantic) indicated that the American continent is moving away from the Euro-Asian landmass. This was the starting-point for the development of a new theory, that of plate tectonics, which has revolutionised the science of geology.
Here we have a further example of the dialectical law of the negation of the negation, as applied to the history of science. Wegener's original theory of continental drift is negated by the steady state theory of isostacy. This in turn is negated by plate tectonics, which marks a return to the older theory but on a qualitatively higher level. Wegener's theory was a brilliant and basically correct hypothesis, but he was unable to explain the exact mechanism whereby continental drift occurs. Now, on the basis of all the discoveries and scientific achievements of the past half-century, we not only know that continental drift is a fact, but we can explain exactly how it takes place. The new theory is on a far higher level than its predecessor, with a deeper understanding of the complex mechanisms through which the planet evolves.
This represents the equivalent in geology of the Darwinian revolution in biology. Evolution applies not only to animate but also to inanimate matter. Indeed, the two interpenetrate and condition each other. Complex natural processes interconnect. Organic matter—life—arises inevitably from inorganic matter at a certain point. But the existence of organic matter in turn exercises a profound effect upon the physical environment. For example, the existence of plants producing oxygen had a decisive effect on the atmosphere and therefore on climatological conditions. The development of the planet and of life on earth provide a wealth of examples of the dialectics of nature, development through contradictions and leaps, long periods of slow “molecular” change alternate with catastrophic developments, from the collision of continents to the sudden extinction of whole species. Moreover, closer examination reveals that the sudden, apparently inexplicable leaps and catastrophes normally have their roots in the earlier periods of slow, gradual change.
What are plate tectonics?
The earth's molten surface eventually cooled down sufficiently to form a crust, under which gas and molten rock were trapped. The surface of the planet was continually broken up by exploding volcanoes, spewing out lava pools. Gradually a thicker crust was formed, entirely made up of volcanic rock. At that time, the first small continents were formed out of the sea of molten rock (magma), and the oceanic crust began to form. Gases and steam from volcanic eruptions began to thin out the atmosphere, causing violent electrical storms. Owing to the higher thermal regime, this was a period of tremendous catastrophes, explosions, with the continental crust forming then being blown apart, then forming again, partial melting, crystal formation and collisions, on a far vaster scale than anything seen since. The first micro-continents moved far faster and collided more frequently than today. There was a rapid process of generation and recycling of the continental crust. The formation of the continental crust was the most fundamental event in the history of the planet. Unlike the seabed, the continental crust is not destroyed by subduction into the mantle, but increases its total volume in the course of time. The creation of the continents was thus an irreversible event.
The earth is made up of a number of layers of material. The main layers are the core (divided into the inner and outer core), the thick mantle, and the thin crust on the surface. Each layer has its own chemical composition and physical properties. As the molten earth cooled some four billion years ago, the heavier materials sank to the earth's centre, while the lighter elements stayed nearer the surface. The earth's inner core is a solid mass, compressed by colossal pressures. The crust forms a thin layer around the semi-liquid mantle, like the skin around an apple. From the cool thin crust, down 50 kilometres, the temperature is about 800°C. Deeper still, at around 2,000 km, the temperature rises to well over 2,200°C. At this depth the rocks behave more like liquids.
This crust supports the oceans and landmasses, as well as all forms of life. About seven-tenths of the crust is covered by water, which is a fundamental feature of the planet. The surface crust is very uneven, containing huge mountain ranges on its landmass, and under water ranges in the deep oceans. An example of one is the Mid-Atlantic Ridge, which forms the boundary between four of the earth's plates. The crust is made up of ten major plates that fit together like a jigsaw puzzle. However, along the edges of these plates “faults” are situated, where volcanic activity and earthquakes are concentrated. The continents are fixed into these plates and move as the plates themselves move.
At the border of these plates underwater volcanoes spew out molten rock from the bowels of the earth, creating new ocean floor. The seabed spreads away from the ridge like a conveyer belt, carrying with it huge rafts of continental crust. Volcanoes are the source of the transformation of enormous energy from the earth into heat. There are an estimated 430 active volcanoes at present. Paradoxically, volcanic explosions release energies that cause the rocks at the crust to melt. The earth's crust (lithosphere) is being continually changed and renewed. New lithosphere is constantly being created by the intrusion and extrusion of magma at the mid-ocean ridges through the partial melting of the mantle (asthenosphere). This creation of new crust at these faults pushes the old floor apart and with it the continental plates. This new lithosphere spreads away from the mid-ocean ridges as more material is added, and eventually, the very expansion of the ocean floor leads elsewhere to it submerging into the earth's interior.
This process explains the movement of continents. The constant subterranean turmoil in turn creates colossal heat, which builds up and produces new volcanic activity. These areas are marked by island arcs and mountain ranges and by volcanoes, earthquakes and deep ocean trenches. This keeps the balance between new and old, in a dialectical unity of opposites. As the plates themselves collide, they produce earthquakes.
This continuous activity under the earth's surface governs many phenomena affecting the development of the planet. The landmass, oceans and atmosphere are not only affected by the sun's rays, but also by gravity and the magnetic field surrounding the earth. “Continual change,” says Engels, “i.e., abolition of abstract identity with itself, is also found in so-called inorganic things. Geology is its history. On the surface, mechanical changes (denudation, frost), chemical changes (weathering), and, internally, mechanical changes (pressure), heat (volcanic), chemical (water, acids, binding substances), in great upheaval, earthquakes, etc.” Again, “Every body is continually exposed to mechanical, physical and chemical influences, which are always changing it and modifying its identity.” 5
Under the Atlantic Ocean there is an undersea volcanic mountain chain where new magma is constantly being created. As a result, the oceanic crust is being enlarged, and is pushing apart the continents of South America and Africa, and also North America and Europe. However, if some areas are getting bigger, others must also be consumed. As the American continent is being pushed by colossal forces against the Pacific Ocean crust, the ocean plate is being forced to dip under America, where it dissolves, moves in currents, and eventually emerges—after millions of years—in another mid-ocean ridge.
These are not smooth, linear processes, but take place through contradictions and leaps of truly cataclysmic dimensions. There are times when the forces beneath the earth's outer crust meet with such resistance that they are forced to turn back upon themselves, and find some new direction. Thus, for a very long period, an ocean like the Pacific can be enlarged. However, when the balance of forces changes, the whole process goes into reverse. A vast ocean can be squeezed between two continents, and eventually disappear, forced between and under the continents. Such processes have occurred many times in the history of the planet over 4,600 million years. Two hundred million years ago, there was an ocean—Iethys—between Euro-Asia and Africa. Today the only remnant of that ocean is part of the Mediterranean Sea. The rest of that great ocean has been consumed and has vanished beneath the Carpathian Mountains and the Himalayas, destroyed by the collision of India and Arabia with Asia.
On the other hand, when a mid-ocean ridge is closed (that is, consumed under a continent) then new lithosphere will appear in another place. As a rule, the lithosphere breaks through at the weakest point. Unimaginable forces accumulate over millions of years, until eventually quantitative change produces a cataclysm. The outer shell is shattered, and the new lithosphere breaks through, opening up the way for the birth of new oceans. In the present day, we can see signs of this process in the volcanic valley of Afar in East Africa, where the continent is breaking up and a new ocean will be created in the next fifty million years. In effect, the Red Sea represents the very early stages in the development of an ocean separating South Arabia from Africa.
The understanding that the earth is not a static but dynamic entity gave a powerful impulse to geology, placing it on a really scientific basis. The great success of the plate tectonics theory is that it dialectically combines all the natural phenomena, overturning the conservative conceptions of the scientific orthodoxy based upon formal logic. Its basic idea is that everything upon earth is in constant movement, and that this takes place through explosive contradictions. Oceans and continents, mountains and basins, rivers, lakes and coastlines are in a process of constant change, in which periods of “calm” and “stability” are violently interrupted by revolutions on a continental scale. Atmosphere, climatic conditions, magnetism, even the location of magnetic poles of the planet are likewise in a permanent state of flux. The development of each individual process is influenced and determined, to one extent or another, by the interconnection with all the other processes. It is impossible to study one geological process in isolation from the rest. All of them combine to create a unique sum total of phenomena which is our world. Modern geologists are compelled to think in a dialectical way although they have never read a single line of Marx and Engels, just because their subject matter can be adequately interpreted in no other way.
Earthquakes and the genesis of mountains
As a young man, Charles Darwin found the fossil of a marine animal far inland. If it were true that marine animals had once lived in this place, then the existing theories of the earth's history were wrong. Darwin showed his find excitedly to an eminent geologist, who replied: “Oh, let's hope it's not true.” The geologist preferred to believe that someone had dropped the fossil there, after a trip to the seaside! From the standpoint of common sense, it appears incredible that continents should move. Our eyes tell us that this is not so. The average velocity for that kind of movement is around 1-2 centimetres a year. Therefore, for normal purposes it may be discounted. However, over a much longer period of millions of years, these slight changes produce the most dramatic changes imaginable.
On the top of the Himalayas (almost 9,000 metres above sea level) there are rocks which contain fossils from marine organisms. This means that these rocks, which originated at the bottom of a prehistoric sea, the Iethys Ocean, were thrust upwards over a period of 200 million years to create the highest mountains in the world. Even this process was not a uniform one, but involved contradictions, with tremendous upheavals, advances and retreats, through thousands of earthquakes, massive destruction, breaks in continuity, deformations and folds. It is evident that the movement of the plates is caused by gigantic forces inside the earth. The entire make-up of the planet, its appearance and identity is determined by this. Humanity has direct experience of only a tiny fraction of these forces through earthquakes and volcanic eruptions. One of the basic features of the earth's surface is the mountain ranges. How do these develop?
Take a bunch of paper sheets and press it against a wall. The sheets will fold and deform under the pressure and they will “move” upwards, creating a curved feature. Now imagine the same process when an ocean is being pressurised between two continents. The ocean is being forced under one of the continents, but the rocks at that point will be deformed and fold, creating a mountain. After the total disappearance of the ocean, the two continents will collide, and the crust at that point will be thickened vertically as the continental masses are compressed. The resistance to subduction causes large nappe folds and thrust faults, and this uplift gives rise to a mountain chain. The collision between the Euro-Asian and the African plates (or parts of Africa) created a long mountain chain, starting from the Pyrenees in the West, passing through the Alps (collision of Italy and Europe), the Balkans, Hellenic, Tauridic, Caucasus (collision of South Arabia and Asia) and finally the Himalayas (collision of India–which was originally an island–and Asia). In the same manner, the Andes and Rocky mountains in America are located over the zone where the Pacific Ocean plate is dipping under the American continent.
It is not surprising that these zones are also characterised by intense seismic activity. The world's seismically active zones are exactly the borders between the different tectonic plates. In particular, zones where mountains are being created signify areas where colossal forces have been accumulated over a long time. When continents collide, we see the accumulation of forces acting on different rocks, at different locations and in different ways. Those rocks, which are composed of the hardest material, resist deformation. But, at a critical point, quantity is transformed into quality, and even the hardest rocks are broken or plastically deformed. This qualitative leap is expressed in earthquakes, which despite the spectacular appearance actually represent only a tiny movement of the earth's crust. The formation of a mountain chain requires thousands of earthquakes, leading to extensive folding, deformation and the movement upwards of rock.
Here we have the dialectical process of evolution through leaps and contradictions. The rocks, which are being compressed, present an initial barrier, offering resistance to the pressure of subterranean forces. However, when they are broken, they turn into their exact opposite, becoming channels for the release of these forces. The forces that operate under the surface are responsible for creating mountain chains and ocean trenches. But on the surface there are other forces operating in the opposite direction.
Mountains do not continuously rise higher and higher, because they are subject to opposing forces. On the surface we have weathering, erosion and transportation of matter from the mountains and the continents back to the oceans. Solid rocks are worn away by the action of strong winds, intense rain, snow and ice, which weaken and fracture the outer shell of the rocks. After a period, there is a further qualitative leap. The rocks gradually lose their consistency, small grains begin to separate from them. The effect of wind and water, especially rivers, transport millions of grains from higher levels to basins, lakes, but mainly oceans, where these rock-particles are gathered together again at the bottom of the sea. There they are buried again, as more and more material is accumulating above them and a new operation appears, the opposite one—rocks are being consolidated again. As a result, new rocks are created, which will follow the movement of the ocean bed until they are once again buried under a continent, where they will melt, possibly emerging once again at the top of a new mountain somewhere in the earth's surface.
The fact that the material under the solid surface is liquid is shown by the lava flows from volcanoes. Rocks are buried very deep in the earth's crust under big mountains and in subduction zones. Under such conditions they suffer a number of changes. As they sink deeper into the crust, the earth's internal activity leads to a rise in temperature. At the same time, the weight of the overlying rocks and mountains leads to a further tremendous increase in pressure. Matter is organised in specific combinations of elements which in the solid state form crystals called minerals. Different minerals come together to form rocks. Every rock has a combination of minerals, and every mineral has a unique combination of elements in a specific crystal form. The changes in temperature and pressure cause changes in the chemistry of most minerals through the substitution of one element for another. While some minerals, within certain limits, remain stable, at a critical point, matter is reorganised in different crystal forms. This causes a qualitative change in the minerals, which react, producing a new combination reflecting the new conditions. This is a qualitative leap, like the change of water to ice at 0°C. The result is that the entire rock is transformed into a new rock. Thus, under the pressure of environmental conditions, we have a sudden leap, involving a metamorphosis not only of minerals but of the rocks themselves. There is no one single mineral form that remains stable under all natural conditions.
In zones which experience the subduction of an ocean under a continent, rocks can be buried very deep in the crust. Under such extreme conditions, the rocks themselves begin to melt. However, this process does not happen all at once. We have the phenomenon of partial melting, because different minerals melt at different points. The melting material has a tendency to move upwards, since it is less dense than the surrounding rocks. But this movement is not without problems, owing to the resistance of the overlying rocks. The molten rock, or magma, will slowly move upwards until, faced with a solid barrier, it is temporarily forced to halt. In addition, the outer area of the magma will start to cool and consolidate into a solid layer that will act as an additional barrier in the path of the magma. But eventually, the elemental force of pressure from below gradually increases to a point where the barriers are broken, and the magma finally breaks through to the surface in a violent explosion, realising colossal pent-up forces.
It is therefore evident that these processes do not take place in an accidental way, as it may appear to the unfortunate victims of an earthquake, but correspond to fundamental laws, which we are now only beginning to understand. They take place in specific zones, located at the borders of the plates, especially in mid-ocean ridges and behind subduction zones. This is exactly the reason why there are active volcanoes in Southern Europe (Santorini in Greece, Etna in Italy), in Japan, where there are subduction zones (which led to the Kobe earthquake), in mid-Atlantic and the Pacific Ocean (volcanic islands and submerged volcanoes in mid-ocean ridges) and in East Africa (Kilimanjaro) where there is a continental drift and the creation of a new ocean.
It is well known to miners that the temperature of the earth's crust increases the further down you go. The main source of this immense heat, which is responsible for all the processes that take place in the bowels of the earth, is heat energy released by the decay of radioactive elements. Elements contain isotopes (atoms of the same element, but with different mass), some of which are radioactive—that is to say, they are unstable and break down with time—producing more heat and more stable isotopes. This continuous process of reaction is proceeding very slowly, because these isotopes have been decaying since the origin of the earth, when they must have been more abundant. Thus, heat production and heat flow must have been higher than at present, maybe two or three times more during the Archaean period than now.
The Archaean-Proterozoic boundary is likewise of major significance, representing a qualitative leap. Not only do we have the emergence of the first life-forms, but also another crucial change in the land mass—from many small continental plates in the Archaean, with its numerous plate collisions, to the formation of larger, thicker and more stable plates during the Proterozoic. These large continental masses were the result of the aggregation of many small proto-continental plates. This was the period of major mountain building, of which two major episodes can be distinguished—1.8 billion and one billion years ago. The remnant of the last event of this titanic process, in which the rocks were repeatedly metamorphosed, deformed and re-shaped, can be seen today in South Canada and North East Norway.
The gradualist theory of uniformitarianism, originally advanced by Hutton in 1778, has no application whatsoever to the early history of the earth. All the available evidence suggests that modern-style plate tectonics began in the early Proterozoic, whilst some earlier variant of the plate tectonic process seems most likely to have been in operation in Archaean times. More than 80 per cent of the present continental crust was created before the end of the Proterozoic period. Plate tectonics is the determining factor in all these processes. Mountain building, earthquakes, volcanoes and metamorphosis are all interconnecting processes, one depends on the other, each determines, influences, causes or is caused by the other, and all of them, taken together, constitute the evolution of the earth.
1. Westbroek, P. Life as a Geological Force, p. 71.↩
2. Engels, The Dialectics of Nature, p. 39, note.↩
3. Westbroek, P. op. cit., pp. 71-2.↩
4. Ibid op. cit., p. 84.↩
5. Engels, F. Dialectics of Nature, 1946 edition, p. 163 and p. 162.↩