David Pratt, in the NCGT journal (March, 2013), see www.ncgt.org/newsletter.php … says there have been numerous finds of old continental crust in the Atlantic, Pacific and Indian oceans (and remember the post last week where some new old continent was found near Mauritius). He says this contradicts the claim the present ocean floors are of fairly recent origin (or at least post-Jurassic). This evidence alone, he assures the reader, contradicts the idea of continents drifting thousands of miles around the surface of the Earth. It is also fatal to the expanding Earth theorists – which is a bit of a relief. They claim the areas occupied by the present oceans simply did not exist 200 million years ago – when the Earth was suppposedly somewhat smaller. Plate Tectonics theory explains these away as 'new spreading blocks' left behind by drifting, associated with transform faults. These are interesting fault zones and not altogether making sense within the sea floor spreading model. Mostly, this evidence of bits of crust is ignored, he says. However, the latest find was definitely not ignored – and reported in mainstream sources. However, as far as Plate Tectonics theory and the consensus is concerned these off bits of old continent are contrary to the model and therefore figure in a very small way in the literature. The recent discovery was heralded as unusual when the opposite is true – there are an awful lot of bits of old continental crust hanging around on the sea bed when they should have suffered the fate of that gaping jaw, the subduction zone. I don't suppose it is in any way terminal to the Plate Tectonics theory which appears to be extremely popular amongst geologists but it is worth noting that Palaeozoic and Proterozoic igneous rock were recovered in cores on the Mid Atlantic Ridge and the Bermuda Rise (where all the new ocean crust in the Atlantic is thought to be oozing out). The consensus response to this discovery, at the time, was that the age of the rock was disputed – it had to be wrong as it contradicted the theory. The site could not contain rock that was older than 10 million years ago, it was said – and yet it does. Pratt presents a raft of evidence of older rocks where Plate Tectonics would demand a much younger age. Ocean floor samples and drilling, seismic data, palaeocurrent and sediment provenance data as well as ocean bed flora and fauna, indicate there used to be, now submerged, continental land masses in the present oceans. Many islands and ocean plateaus with semi continental crust appear to be remnants of much larger 'palaeo-lands'.
If the sea floor spreading paradigm is wrong so is the subduction hypothesis. Lots of evidence exists, he assures the reader, to suggest so. Plate Tectonics theory and a geologically young ocean crust and vast continental displacements is supposedly supported by marine magnetic anomalies – alternating bands of slightly high and lower magnetic intensity on either side of ocean ridges (supposedly produced by sea floor spreading in combination with global magnetic reversals). However, the bands are found on only 70 per cent of seismically active mid ocean ridges and they are hardly as linear as shown in text book examples of the phenomenon. They are often quite opposite to being linear lines – very often oblique to the ridge. The bands are also local where no ridge systems exist and can be explained by other means than sea floor spread.
According to Plate Tectonics the Earth's outer shell, or lithosphere, is divided into 13 plates. That is how it all began but since then lots of very small plates have been added to account for palaeomagnetic poles and other discrepancies that have come to light. The lithosphere is said to move over a hotter more liquid mass known as the asthenosphere. They even tell us how thick the lithosphere is – 70km on the ocean sea bed and between 125 and 250km on the continents. The asthenosphere thickness is guesswork and is argued over. Seismic tomagraphy, which produces 3 dimensional images of the interior of the Earth has indicated continental lithosphere can extend, in places, to as much as 400km deep, like the big roots on molar teeth. In addition, geophysical data appears to show the asthenosphere is not a continuous layer but is made up of disconnected lenses which are observed mainly in regions of tectonic activity and high heat flow. There are also close correlations between near surface geological features, crustal structures, heat flow, geoid anomalies, and inhomogeneities in both the upper and lower mantle. These appear to remain stable for long periods of geological time which would then appear to contradict the idea of lithosphere plates continually moving around – albeit at a minute rate of knots.
You get none of the uncertainty involved reading your average text book on geology. Pratt appears to shed light on what is generally regarded almost as a closed subject. Just as the base of lithospheric plates is often ill defined, he continues, some plate boundaries are likewise ill defined – some are even non-existent (arguable, perhaps) and lists the discrepancies as he sees them. In addition, whereas plate boundaries were intially reckoned to be fairly narrow affairs their width, as a result of evidence in the field, is now said to be hundreds of m to thousands of km and have been dubbed 'diffuse plate boundaries' (which sounds like a bit of a cop out). These are thought to cover some 15 per cent of the surface of the Earth – and that is a lot of space without a plate.
The Earth's topography ranges from 8.8km above sea level to 10.8km below it. Mantle heat flow and transport can cause significant changes in crustal thickness, composition , density, and so on, which can result in substantial uplift or subsidence. In other words, the land can actually go up and down just as a result of the flow of heat in the mantle. Is it possible this can cause sea levles to appear to rise during cooling or warming periods, the land sinking and the seas appearing to rise?
This all happens without the need for plates colliding with each other or subduction. The scale of vertical movement, or uplift, is immense in some place, as marine sediments and layering in mountainous regions seem to show. As far as horizontal movement is concerned, plates actually moving across the face of the Earth, evidence exists to show plates can be thrust sidewards for considerable distances, at what are called wrench faults. However, as the lithosphere varies substantially in thickness, the existence of deep continental roots, the lack of a continuous asthenosphere and the absence in some places of plate boundaries (where theory dictates they should occur) as well as the correlation between near surface features and deep mantle features, all this inhibits the idea that huge lithosphere slabs, the plates, move over hundreds of thousands of km and yet Plate Tectonics advocates and the consensus shirt tail hangers-on, are convinced their models of plate motion are supported by palaeomagnetic data and marine anomalies, even space geodetic data – in spite of the serious discrepancies noted above.
Computer simulation seems to rule the roost at this branch of science – replicating the situation in climate science. No wonder the two are already bound up with each other. Naomi Oreskes, writer of an important textbook on Plate Tectonics, is also prominent in pushing the greenhouse gas theory of global warming. In fact, it is that trace gas, co2, that binds the two as Plate Tectonics relies on high levels of co2 during the Dinosaur age to account for warming at the Poles – which otherwise would be anomalous.
Pratt warms further to the subject by adding that geologists and geophysicists tend to treat pieces of the Earth's crust like a roomful of furniture on their computer screens, which can be pushed around here and there. The Day of the Geeks is upon us it would seem.
Pratt also says the Earth's crust cannot easily be manipulated, particularly if physical laws of motion are taken into account. The rigid crust and uppermost mantle form a massive interlocking mosaic. Objects within that mosaic are moved substantial distances as geological field mapping allows – but the movements are both vertical and horizontal. That may have no bearing on the hypothesis that huge slabs or plates up to 200km thick and thousands of km wide, weiging an enormous sum of tons, can be moved freely and systematically about the surface of the Earth in defiance of basic physical constraints.
Pratt is a sceptic (of Plate Tectonics) and marshals his evidence very well. Thus, he turns his eye to the Super Contient. Palaeomagnetic data is one of the reasons why Plate Tectonicists believe there have been at least three supercontinents – with Pangaea the last of them. Once again Pratt is somewhat devastating in his critique – how do you get all the continents to join up and come together as one whole. Easy to achieve on a computer screen – but how about real life. According to the theory the various blocks, in between, expanded out and retracted, did their thing and then reassembled once again. Pangaea, the third supercontinent formation, allegedly came into being at 300 to 250 million years ago (give a few days either way). The first major break-up of Pangaea occurred in the Jurassic – and Pratt produces several pages of images and graphs and maps to pieces of continent coming together and then drawing apart. It is at this point you begin to realise how complicated it all is – pieces of land being moved around solely because of geomagnetic anomalies that could mean something quite different to what is being claimed.
At this point, also, Pratt introduces a very nice nuance (page 91 of the journal), but bigger than a nuance ought to be. This involves the distribution of the land and sea in the modern world. Pangaea involves a totally lopsided arrangement of the continents and oceans which is in direct contrast to the modern arrangement of sea and land – which is balanced. Firstly, you will need a world map, or better, a globe. The continents tend to be triangular in shape with their points towards the south. Secondly, the North Pole is almost entirely ringed by land while at the South Pole the Antarctic continent, in contrast, is ringed by water – the opposite effect. Now, various geologists have observed this arrangement and gone on to take it one stage further – with some surprising results. The oceans and the continents are also arranged antipodally – there is land in one area of the globe, there tends to be water in the corresponding area on the opposite side of the globe. Easy to spot when you look for it and mentioned as early as 1899 (Gregory), in 1933 by Bucher and in 1950 by Steers, for example. The Arctic is antipodal to the Antarctic; N America is continental to the Indian Ocean; Europe and Africa to the central Pacific; Australia to the small basin of the N Atlantic, while the S Atlantic corresponds to East Asia (less exactly so, or not completely, but a huge continental shelf lies offshore). Just 6 per cent of the Earth does not comply to the antipodal theory. Harrsion et al (1968) calculated there is a 1 in 14 probability that this arrangement is the result of chance – which means a larger than life probability it has a purpose of some kind. We may note this arrangement is also incompatible with polar wander theory as well as continental drift. Interestingly, Gregory (1899) speculated that in the Upper Palaeozoic the tetrahadron effect of land arrangement may have been the other way up (upside down). Meyerhoff (1995) thought the continents may have reached their present positions in a molten Earth very early in its history and is perhaps in response to the Earth's rotation, with the surface masses distributed more or less axisymmetrically for rotational stability. In reality the field is wide open to reinterpretation and some young buck may come up with a surprise or two. The question is – was there a roughly antipodal distribution of land and sea in the geological past when parts of the present continents were submerged and land masses existed in parts of the present oceans.
I'm warming to this subject and there is a long way to go. I shall do another post next week some time.