Article 60

Belief De-Throned By Knowledge.

Having recognised in Articles 58 and 59 that knowledge is currently subjugated by belief to the extent of being publishable only through the mouths of fictitious characters in the form of novels, I now draw my readers’ attention to a further example of this subjugation provided bythe publisher’s disclaimer which appears in the book The Geology of Britainby Peter Toghill re-published by Airlife Publishing in 2012. This disclaimer is that ‘the information in this book is true and complete to the best of our knowledge’; but that ‘all recommendations are made without any guarantee on the part of the Publisher, who also disclaims any liability incurred in connection with the use of this data or specific details’. Given that some of its diagrams are those of Course S 26, Historical Geology, of the Open University, this disclaimer astonishes me, and causes me to wonder (rhetorically) whether such graduates in geology reproduce such knowledge only to obtain their degrees, and disclaim it, and retain beliefs counter to it, thereafter.

Be that as it may, I now use the above book to demonstrate how geology uses the demonstrable knowledge of physicochemical science to replace nineteenth century biblical belief in a young, 4000 year old, Earth with the demonstrable knowledge that the Earth is very old, in fact, millions of years old; that the early belief which assumed that every feature of the Earth’s surface was formed by catastrophic action or biblical flood was replaced by uniformitarianism in which the Earth’s surface changed immeasurably slowly; and that the processes which formed rocks and geological features in the past are still active today at the same slow rates; that the present is the key to the past; that we can explain all ancient features in terms of current processes; and that the recent discovery of plate tectonics now replaces all previous uniformitarian theories (beliefs). The introduction to this book recalls that James Hutton, a member of the Scottish Enlightenment, began to study geological features around Edinburgh and at Siccar point on the Berwickshire coast, where he observed what is now called an unconformity, a structural difference between two sedimentary rock sequences caused by a period of uplift and erosion between the formations of the two sequences. As of now, we know that such an unconformity is evidence of a long time interval. In the Siccar point case, it is about 50 million years. However, without knowing anything about such time intervals, Hutton recognised that one sequence had been laid down, hardened, folded and eroded before the next was laid down on top, and in looking at these exposures, he reported in 1788 that in terms of Earth history, he could see ‘no vestige of a beginning and no prospect of an end’, an observation which brings us to the recognition and measurement of geological timescales.

It was William Smith, often called the ‘father of stratigraphy, who while constructing canals in southern England in the early 1800s, observed that each layer of rock contained a distinct layer of fossils; and that strata could thus be recognised elsewhere by the fossils they contain. Thus, it became possible in the 1800s to recognise different levels in the enormous rock sequence covering Britain from the fossils they contained, and on this basis, observers such as William Smith, had enabled Smith to produce a geological map of England and Wales by 1815. Such observations, over the whole of Britain, led in turn to the sequence of rocks being recognised, with the oldest on the bottom and youngest on top, which on the basis of fossil content could be divided into a series of major units progressively called eras, periods/systems, and epochs/series of relative time, which were initially named the Palaeosoic, Mesozoic and Cainosoic, i.e. ancient, middle and new life, the three of them comprising the Phanerzoic. In regions of layered sedimentary rocks of sequential periods where folding has occurred, the sequence of layering could be determined without reference to the differing fossil content of the layers.

However, the chemical discovery of radioactivity and its application to geology in the twentieth century, enabled geologists to advance from relative to absolute ages, and thus to discover how old rocks actually are in terms of their formation millions of years ago. In simple terms, we know that when lava solidifies to rock, some grains contain a radioactive isotope of uranium which decays to a non-radioactive isotope of lead; that having measured the constant rate of this decay in the laboratory, we can measure the extent of its progress in our rock sample and thus determine the time interval since its solidification, the constant rate of decay being slow enough for its defined and measured half-life to be capable of measuring time lapses of thousands of millions of years, thus giving the radiometric date of origin, and the unit thus used is given the abbreviation Ma, for millions of years ago. Thus, the Cainozoic Era is now sub-divided into the Quaternary Period/ System which itself is further sub-divided into the Holocene Epoch/Series, (10,000 years ago) the Pleistocene Epoch/Series (2 Ma years ago), the Neogene Epoch/Series (24 Ma), and the Palaeogene Epoch/Series (65 Ma) both of which are further sub-divided to two and three Epochs/Series; while the Mesozoic Era is sub-divided into the Cretaceous (146 Ma), the Jurassic (208 Ma) the Triassic (245 Ma) Periods/Systems; and the Palaeozoic Era is sub-divided into the Permian (290 Ma), the Carboniferous (363 Ma), the Devonian (409 Ma), the Silurian (439 Ma), the Ordovician ( 510 Ma); and the Cambrian(544 Ma) Periods/Systems; while the Precambrian Era is subdivided into Proterozoic (1000 – 2500 Ma), the Archaean (2500 – 3800 Ma) and the Pre-Archaean, (4600 Ma and back to the Formation of Earth). Indeed all of the above Eras are further sub-divided into Epochs and Series, though these need not detain us here. However, before proceeding, we must differentiate the rock-types now classified as igneous, sedimentary and metamorphic.

The very first rocks on the Earth’s surface were formed from the cooling of molten solutions and are termed igneous. The molten material which nowadays comes from shallow depths in the Earth’s mantle, down to 60 kilometres, is called magma. This can come to the surface from a volcano in the form of lava, and when it cools, the resulting igneous rock is often of a chemical composition which we call basalt, good examples from the geological past in Britain can be seen on Mull and in the nearby Fingal’s Cave on the Isle of Staffa. Other types of lava include andesite (common in the Andes) and obsidian. Sometimes lava has already hardened in the volcanic vent and is subsequently thrown out as volcanic ash during volcanic explosions. This ash which is called Tuff if it is from an ancient explosion, can entomb whole areas, as it did at Pompeii. It can also be erupted as a dense incandescent gas cloud which flows down the mountain at great speed and causes great damage, as it did at the eruption in Martinique in 1903, thus killing over 30,000 people. The early stages of the eruption of Vesuvius in AD 79 (Pompeii) were probably of this type.

On the other hand, when areas of the Earth’s crust are exposed as land, and are eroded by the sea, or by rivers, wind or ice, the small particles thus formed are called sediment and this material can be transported away from the source and laid down in layers on the seabed, in lakes, in river estuaries or on land to give great thicknesses of sediment which over long periods of time can be hardened to form sedimentary rocks, which usually have an obvious layered structure. Again, such layered sedimentary rocks have been moved to create the sedimentary rocks of some of world’s highest mountains such as the Canadian Rockies in which the layered structure remains clearly visible. Again, some of the best known sedimentary rocks are sandstones which consist of relatively coarse particles, while shales and mudstones consist of finer clay particles, while limestones are calcareous sedimentary rocks made up of the shells of marine animals and plants with proportional precipitates of calcium carbonate. Indeed, some of the latter include whole fossilised reefs, indicative of their formation in sub-tropical latitudes.

At this point, we have to consider the mechanism by which all of this implied lateral movement is actually achieved, and which is known as plate tectonics. The earliest idea was that of continental drift put forward by Alfred Wegener in 1915, but it was not until the 1960s that an explanation of the mechanism of that drift became available. Since then, geologists have accepted that the Earth’s outer shell, down to around 100 km consists of a number of distinct regions which they now call plates; that these plates move independently of each other, driven by giant convection cells in Earth’s molten interior; that the boundaries of the plates, where they are in contact with each other, are lines of movement (tectonic activity) where one plate is over-riding or sliding past another, or where new molten material, in the form of basalt lava, is coming to the Earth’s surface; that the latter boundaries, now called constructive plate boundaries, occur at mid-ocean ridges where volcanic activity produces a constant conveyor belt of new oceanic crust on either side of the ridge to produce new ocean floor; that the new floor moves continents apart on either side of the ocean; that the constant supply of new ocean-floor would increase the size of the Earth, were the crust material not being dragged back into the Earth at corresponding destructive plate boundaries which take the form of deep ocean trenches which mark the route of these returns; that this process is called subduction to denote that one plate is descending below another; that such subduction zones are areas of intense earthquake and tectonic activity where the rocks are folded, faulted, altered (metamorphosed) and melted to form new igneous rocks; that the world’s major earthquakes and volcanoes are associated with subduction zones; but that some of the most intense earthquake activity occurs where one plate is sliding past another along major breaks in the crust called transform faults; that such boundaries are called conservative boundaries; that the best known is the San Andreas Fault in California; that fold mountains and volcanoes are also formed on the leading edge of the plate which is over-riding the other if it is of continental material; that this is happening in the Andes of South America; and that island arcs occur when the two colliding plates are both oceanic areas, as in the East Indies today; that sea-floor spreading is certainly driven by convection cells causing a ‘push’ effect at ocean ridges; but that widening is also caused by a pull’ effect as cold dense plates slide down subduction zones due to gravity; and finally that the process of sea-floor spreading which causes new oceans to form and grow, also leads to the destruction of older oceans; and that the end product of the latter process is that the two continents previously on either side of the old ocean, finally collide to form a huge fold-mountain chain as in today’s Himalayas.

The foregoing now brings us to the great breakthrough in plate tectonics of the 1960s which related sea-floor spreading to magnetic anomalies, and thus introduced a means of deducing the rate of such spreading and of the associated continental drift. This breakthrough came about from observing that that Earth’s magnetic field repeatedly reverses its polarity every few hundred thousand years or so; and that there are large intervals of time when the field was opposite to what it is today- when a compass needle would have pointed to the south magnetic pole; and that a study of basalt lavas dated by the radioactive method on land going back over four million years would produce a timescale for these reversals; that studies of ocean floor in the vicinity of mid-ocean ridges showed them to be entirely basalt and to have a striped pattern of magnetic anomalies symmetrical about the ridge axis with strengths of the field greater and less than the average and it was shown by Vine and Matthews in 1963, following work by Hess in 1960 that these stripes corresponded to normal and reversed polarity in the basalts of the ocean floor. Hess had suggested that basaltic ocean crust was newly created at ocean ridges, and a comparison of the striped pattern on either side of the ridge axis on the ocean floor showed it to be identical with the pattern found in basalt lavas found on land. Thus, by calculating how far a particular stripe was from the ocean ridge and knowing the age of this stripe from continental lavas, it was shown how far the stripe had moved in so many million years from the ridge from which it had originated. Thus, sea-floor spreading rates are known to vary from 2cm per year in the North Atlantic to 20cm per year in the North Pacific, these being the amounts of movement on either side of the ocean ridge.

Sea-floor spreading is the mechanism by which oceans widen and push continents apart. However, all ocean crust is eventually destroyed at subduction zones where it dives back down to the mantle. Hess suggested that mid-ocean ridges were ephemeral structures having a life of 200 – 300 million years; and in fact nowhere on the Earth today is there any ocean crust older than 200 million years- all earlier ocean crust having been destroyed by earlier subductions. However, evidence for oceans up to 500 million years old comes from marine sediments which have not been subducted, old volcanic island arcs, and rare pieces of oceanic crust, called ophiolites, which are preserved within continents. In addition, we can see how continents have moved through various latitudes and climates in the past, as these continents have been pushed around by sea-floor spreading within oceans long since destroyed. All of the effects of plate tectonics can be seen happening somewhere on Earth today. Where we see these effects in older rocks we can conclude that these areas were at plate boundaries in the past. Thus, in examining the geology of Britain, we can see for instance the great thicknesses of volcanic lavas and ashes of Snowdonia which were formed between 500 and 450 million years ago, these being the products of a destructive plate margin where an oceanic plate was subducted under another to form a series of volcanic islands as material melted at depth. The volcanic ashes often fell into the sea and entombed animals of the seabed, which are now found as fossils on the very summit of Snowdon, while a modern example is the volcanic island arc of the East Indies and the teeming life of its surrounding oceanic area. Again, by analysing the chemistry of rocks we can identify trace element differences between volcanic rocks from continental areas such as the Andes and those from oceanic areas such as the East Indies and by such means show that those from Snowdonia and the older lavas from Shropshire, the Wrekin, etc., are from island arcs while those from the Midland Valley of Scotland are of continental origin.

Yet again, we can show that the Great Glen Fault in Scotland may mark the site of an old conservative plate boundary where one plate slid past another around 400-350 million years ago and caused enormous earthquakes, analogous to the San Andreas Fault in California, where the Pacific plate is moving northwards by sliding past the North American plate and causing numerous earthquakes. Furthermore the old fold mountain chain which covers the Scottish Highlands is an example of an ancient continental collision around 400 Ma in closing an ancient ocean and folding mountains up to 8000m high in a process exactly like that which more recently raised the Himalayas when the India plate collided with Asia about 20 Ma with the closure of another ocean. Again, we see that the geological sequence in Britain shows evidence of rocks produced in a variety of climates from cold temperate, through sub-tropical to Sahara-like deserts and tropical rain forests; that instead of proposing widespread global climate changes in the past, we can simply say that Britain has drifted northwards during the last 500 million years from a position in the southern hemisphere with southern Britain near the Antarctic circle, across the equator and into the northern hemisphere to reach its present latitude around 50 Ma. Since then, movement following the birth of the Atlantic has been eastwards. Indeed, Britain probably spent 300 of these 500 million years in the tropics which explains its former coral reefs, coal generating forests and Sahara-like deserts.

However, the foregoing assumes that the Earth has usually had the same climatic conditions and temperature differences between the poles and the equator as it does now. Yet it appears that during the last 1000 million years the Earth has been warmer than it is today; but that during four particular periods there has been major cooling periods which produced Ice Ages; that we are now living in the most recent of these cooler periods; that it has been in effect for about two million years; that during this current period the Earth is cooler than usual; that the more normal condition is for there to be no ice at the poles and for sea levels to be correspondingly higher; and that during the colder periods, oceanic water is trapped in continental polar ice caps with sea levels being correspondingly lower; and that because of our position ne

Article 60: Belief Dethroned By Knowledge.

Having recognised in Articles 58 and 59 that knowledge is currently subjugated by belief to the extent of being publishable only through the mouths of fictitious characters in the form of novels, I now draw my readers’ attention to a further example of this subjugation provided bythe publisher’s disclaimer which appears in the book The Geology of Britainby Peter Toghill re-published by Airlife Publishing in 2012. This disclaimer is that ‘the information in this book is true and complete to the best of our knowledge’; but that ‘all recommendations are made without any guarantee on the part of the Publisher, who also disclaims any liability incurred in connection with the use of this data or specific details’. Given that some of its diagrams are those of Course S 26, Historical Geology, of the Open University, this disclaimer astonishes me, and causes me to wonder (rhetorically) whether such graduates in geology reproduce such knowledge only to obtain their degrees, and disclaim it, and retain beliefs counter to it, thereafter.

Be that as it may, I now use the above book to demonstrate how geology uses the demonstrable knowledge of physicochemical science to replace nineteenth century biblical belief in a young, 4000 year old, Earth with the demonstrable knowledge that the Earth is very old, in fact, millions of years old; that the early belief which assumed that every feature of the Earth’s surface was formed by catastrophic action or biblical flood was replaced by uniformitarianism in which the Earth’s surface changed immeasurably slowly; and that the processes which formed rocks and geological features in the past are still active today at the same slow rates; that the present is the key to the past; that we can explain all ancient features in terms of current processes; and that the recent discovery of plate tectonics now replaces all previous uniformitarian theories (beliefs). The Introduction to this book recalls that James Hutton, a member of the Scottish Enlightenment, began to study geological features around Edinburgh and at Siccar Point on the Berwickshire coast, where he observed what is now called an unconformity, a structural difference between two sedimentary rock sequences caused by a period of uplift and erosion between the formations of the two sequences. As of now, we know that such an unconformity is evidence of a long time interval. In the Siccar Point case, it is about 50 million years. However, without knowing anything about such time intervals, Hutton recognised that one sequence had been laid down, hardened, folded and eroded before the next was laid down on top, and in looking at these exposures, he reported in 1788 that in terms of Earth history, he could see ‘no vestige of a beginning and no prospect of an end’, an observation which brings us to the recognition and measurement of geological timescales.

It was William Smith, often called the ‘father of stratigraphy, who while constructing canals in southern England in the early 1800s, observed that each layer of rock contained a distinct layer of fossils; and that strata could thus be recognised elsewhere by the fossils they contain. Thus, it became possible in the 1800s to recognise different levels in the enormous rock sequence covering Britain from the fossils they contained, and on this basis, observers such as William Smith, had enabled Smith to produce a geological map of England and Wales by 1815. Such observations, over the whole of Britain, led in turn to the sequence of rocks being recognised, with the oldest on the bottom and youngest on top, which on the basis of fossil content could be divided into a series of major units progressively called eras, periods/systems, and epochs/series of relative time, which were initially named the Palaeosoic, Mesozoic and Cainosoic, i.e. ancient, middle and new life, the three of them comprising the Phanerzoic. In regions of layered sedimentary rocks of sequential periods where folding has occurred, the sequence of layering could be determined without reference to the differing fossil content of the layers.

However, the chemical discovery of radioactivity and its application to geology in the twentieth century, enabled geologists to advance from relative to absolute ages, and thus to discover how old rocks actually are in terms of their formation millions of years ago. In simple terms, we know that when lava solidifies to rock, some grains contain a radioactive isotope of uranium which decays to a non-radioactive isotope of lead; that having measured the constant rate of this decay in the laboratory, we can measure the extent of its progress in our rock sample and thus determine the time interval since its solidification, the constant rate of decay being slow enough for its defined and measured half-life to be capable of measuring time lapses of thousands of millions of years, thus giving the radiometric date of origin, and the unit thus used is given the abbreviation Ma, for millions of years ago. Thus, the Cainozoic Era is now sub-divided into the Quaternary Period/ System which itself is further sub-divided into the Holocene Epoch/Series, (10,000 years ago) the Pleistocene Epoch/Series (2 Ma years ago), the Neogene Epoch/Series (24 Ma), and the Palaeogene Epoch/Series (65 Ma) both of which are further sub-divided to two and three Epochs/Series; while the Mesozoic Era is sub-divided into the Cretaceous (146 Ma), the Jurassic (208 Ma) the Triassic (245 Ma) Periods/Systems; and the Palaeozoic Era is sub-divided into the Permian (290 Ma), the Carboniferous (363 Ma), the Devonian (409 Ma), the Silurian (439 Ma), the Ordovician ( 510 Ma); and the Cambrian(544 Ma) Periods/Systems; while the Precambrian Era is subdivided into Proterozoic (1000 – 2500 Ma), the Archaean (2500 – 3800 Ma) and the Pre-Archaean, (4600 Ma and back to the Formation of Earth). Indeed all of the above Eras are further sub-divided into Epochs and Series, though these need not detain us here. However, before proceeding, we must differentiate the rock-types now classified as igneous, sedimentary and metamorphic.

The very first rocks on the Earth’s surface were formed from the cooling of molten solutions and are termed igneous. The molten material which nowadays comes from shallow depths in the Earth’s mantle, down to 60 kilometres, is called magma. This can come to the surface from a volcano in the form of lava, and when it cools, the resulting igneous rock is often of a chemical composition which we call basalt, good examples from the geological past in Britain can be seen on Mull and in the nearby Fingal’s Cave on the Isle of Staffa. Other types of lava include andesite (common in the Andes) and obsidian. Sometimes lava has already hardened in the volcanic vent and is subsequently thrown out as volcanic ash during volcanic explosions. This ash which is called Tuff if it is from an ancient explosion, can entomb whole areas, as it did at Pompeii. It can also be erupted as a dense incandescent gas cloud which flows down the mountain at great speed and causes great damage, as it did at the eruption in Martinique in 1903, thus killing over 30,000 people. The early stages of the eruption of Vesuvius in AD 79 (Pompeii) were probably of this type.

On the other hand, when areas of the Earth’s crust are exposed as land, and are eroded by the sea, or by rivers, wind or ice, the small particles thus formed are called sediment and this material can be transported away from the source and laid down in layers on the seabed, in lakes, in river estuaries or on land to give great thicknesses of sediment which over long periods of time can be hardened to form sedimentary rocks, which usually have an obvious layered structure. Again, such layered sedimentary rocks have been moved to create the sedimentary rocks of some of world’s highest mountains such as the Canadian Rockies in which the layered structure remains clearly visible. Again, some of the best known sedimentary rocks are sandstones which consist of relatively coarse particles, while shales and mudstones consist of finer clay particles, while limestones are calcareous sedimentary rocks made up of the shells of marine animals and plants with proportional precipitates of calcium carbonate. Indeed, some of the latter include whole fossilised reefs, indicative of their formation in sub-tropical latitudes.

At this point, we have to consider the mechanism by which all of this implied lateral movement is actually achieved, and which is known as plate tectonics. The earliest idea was that of continental drift put forward by Alfred Wegener in 1915, but it was not until the 1960s that an explanation of the mechanism of that drift became available. Since then, geologists have accepted that the Earth’s outer shell, down to around 100 km consists of a number of distinct regions which they now call plates; that these plates move independently of each other, driven by giant convection cells in Earth’s molten interior; that the boundaries of the plates, where they are in contact with each other, are lines of movement (tectonic activity) where one plate is over-riding or sliding past another, or where new molten material, in the form of basalt lava, is coming to the Earth’s surface; that the latter boundaries, now called constructive plate boundaries, occur at mid-ocean ridges where volcanic activity produces a constant conveyor belt of new oceanic crust on either side of the ridge to produce new ocean floor; that the new floor moves continents apart on either side of the ocean; that the constant supply of new ocean-floor would increase the size of the Earth, were the crust material not being dragged back into the Earth at corresponding destructive plate boundaries which take the form of deep ocean trenches which mark the route of these returns; that this process is called subduction to denote that one plate is descending below another; that such subduction zones are areas of intense earthquake and tectonic activity where the rocks are folded, faulted, altered (metamorphosed) and melted to form new igneous rocks; that the world’s major earthquakes and volcanoes are associated with subduction zones; but that some of the most intense earthquake activity occurs where one plate is sliding past another along major breaks in the crust called transform faults; that such boundaries are called conservative boundaries; that the best known is the San Andreas Fault in California; that fold mountains and volcanoes are also formed on the leading edge of the plate which is over-riding the other if it is of continental material; that this is happening in the Andes of South America; and that island arcs occur when the two colliding plates are both oceanic areas, as in the East Indies today; that sea-floor spreading is certainly driven by convection cells causing a ‘push’ effect at ocean ridges; but that widening is also caused by a pull’ effect as cold dense plates slide down subduction zones due to gravity; and finally that the process of sea-floor spreading which causes new oceans to form and grow, also leads to the destruction of older oceans; and that the end product of the latter process is that the two continents previously on either side of the old ocean, finally collide to form a huge fold-mountain chain as in today’s Himalayas.

The foregoing now brings us to the great breakthrough in plate tectonics of the 1960s which related sea-floor spreading to magnetic anomalies, and thus introduced a means of deducing the rate of such spreading and of the associated continental drift. This breakthrough came about from observing that that Earth’s magnetic field repeatedly reverses its polarity every few hundred thousand years or so; and that there are large intervals of time when the field was opposite to what it is today- when a compass needle would have pointed to the south magnetic pole; and that a study of basalt lavas dated by the radioactive method on land going back over four million years would produce a timescale for these reversals; that studies of ocean floor in the vicinity of mid-ocean ridges showed them to be entirely basalt and to have a striped pattern of magnetic anomalies symmetrical about the ridge axis with strengths of the field greater and less than the average and it was shown by Vine and Matthews in 1963, following work by Hess in 1960 that these stripes corresponded to normal and reversed polarity in the basalts of the ocean floor. Hess had suggested that basaltic ocean crust was newly created at ocean ridges, and a comparison of the striped pattern on either side of the ridge axis on the ocean floor showed it to be identical with the pattern found in basalt lavas found on land. Thus, by calculating how far a particular stripe was from the ocean ridge and knowing the age of this stripe from continental lavas, it was shown how far the stripe had moved in so many million years from the ridge from which it had originated. Thus, sea-floor spreading rates are known to vary from 2cm per year in the North Atlantic to 20cm per year in the North Pacific, these being the amounts of movement on either side of the ocean ridge.

Sea-floor spreading is the mechanism by which oceans widen and push continents apart. However, all ocean crust is eventually destroyed at subduction zones where it dives back down to the mantle. Hess suggested that mid-ocean ridges were ephemeral structures having a life of 200 – 300 million years; and in fact nowhere on the Earth today is there any ocean crust older than 200 million years- all earlier ocean crust having been destroyed by earlier subductions. However, evidence for oceans up to 500 million years old comes from marine sediments which have not been subducted, old volcanic island arcs, and rare pieces of oceanic crust, called ophiolites, which are preserved within continents. In addition, we can see how continents have moved through various latitudes and climates in the past, as these continents have been pushed around by sea-floor spreading within oceans long since destroyed. All of the effects of plate tectonics can be seen happening somewhere on Earth today. Where we see these effects in older rocks we can conclude that these areas were at plate boundaries in the past. Thus, in examining the geology of Britain, we can see for instance the great thicknesses of volcanic lavas and ashes of Snowdonia which were formed between 500 and 450 million years ago, these being the products of a destructive plate margin where an oceanic plate was subducted under another to form a series of volcanic islands as material melted at depth. The volcanic ashes often fell into the sea and entombed animals of the seabed, which are now found as fossils on the very summit of Snowdon, while a modern example is the volcanic island arc of the East Indies and the teeming life of its surrounding oceanic area. Again, by analysing the chemistry of rocks we can identify trace element differences between volcanic rocks from continental areas such as the Andes and those from oceanic areas such as the East Indies and by such means show that those from Snowdonia and the older lavas from Shropshire, the Wrekin, etc., are from island arcs while those from the Midland Valley of Scotland are of continental origin.

Yet again, we can show that the Great Glen Fault in Scotland may mark the site of an old conservative plate boundary where one plate slid past another around 400-350 million years ago and caused enormous earthquakes, analogous to the San Andreas Fault in California, where the Pacific plate is moving northwards by sliding past the North American plate and causing numerous earthquakes. Furthermore the old fold mountain chain which covers the Scottish Highlands is an example of an ancient continental collision around 400 Ma in closing an ancient ocean and folding mountains up to 8000m high in a process exactly like that which more recently raised the Himalayas when the India plate collided with Asia about 20 Ma with the closure of another ocean. Again, we see that the geological sequence in Britain shows evidence of rocks produced in a variety of climates from cold temperate, through sub-tropical to Sahara-like deserts and tropical rain forests; that instead of proposing widespread global climate changes in the past, we can simply say that Britain has drifted northwards during the last 500 million years from a position in the southern hemisphere with southern Britain near the Antarctic circle, across the equator and into the northern hemisphere to reach its present latitude around 50 Ma. Since then, movement following the birth of the Atlantic has been eastwards. Indeed, Britain probably spent 300 of these 500 million years in the tropics which explains its former coral reefs, coal generating forests and Sahara-like deserts.

However, the foregoing assumes that the Earth has usually had the same climatic conditions and temperature differences between the poles and the equator as it does now. Yet it appears that during the last 1000 million years the Earth has been warmer than it is today; but that during four particular periods there has been major cooling periods which produced Ice Ages; that we are now living in the most recent of these cooler periods; that it has been in effect for about two million years; that during this current period the Earth is cooler than usual; that the more normal condition is for there to be no ice at the poles and for sea levels to be correspondingly higher; and that during the colder periods, oceanic water is trapped in continental polar ice caps with sea levels being correspondingly lower; and that because of our position near to plate-boundaries in the past, our differing latitudes, and the great variety of rock-types and structures which have resulted, we have been able to understand the fundamental principles of geology and to use plate tectonics to understand and explain past events.

At this point in time we recognise eleven plates, the Eurasian, the North American, the South American, the Scotia, the African, the Arabian, the Indian-Australian, the Philippine Sea, the Pacific, the Cocos, the Nazca, and the Antarctic. At this point, it is interesting to note that Scotland, north of the Great Glen was once on the edge of the North American plate while the rest of mainland Britain was on the edge of the Antarctic plate. 18/6/21

ar to plate-boundaries in the past, our differing latitudes, and the great variety of rock-types and structures which have resulted, we have been able to understand the fundamental principles of geology and to use plate tectonics to understand and explain past events.

At this point in time we recognise eleven plates, the Eurasian, the North American, the South American, the Scotia, the African, the Arabian, the Indian-Australian, the Philippine Sea, the Pacific, the Cocos, the Nazca, and the Antarctic. At this point, it is interesting to note that Scotland, north of the Great Glen was once on the edge of the North American plate while rest of mainland Britain was on the edge of the Antarctic plate. 18/6/21.

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