EP311: Life On Demi-Earth
Ben Franklin Centre for Theoretical Research
PO Box 27, Subiaco, WA 6008, Australia.
This article is about the state of our planet at a critical point in its past history -- 200 million years ago, when the Earth was still only half its current diameter. That time, some 200 million years ago, is relatively recent in geological terms. The Earth, as a planet, is believed to have formed about 4700 million years ago, so its status as "Demi-Earth", with half its current radius, is quite late on in its life.
The time of Demi-Earth, at the start of the Jurassic Period, marks a particular milestone in the Earth's development. Prior to this, continental Crust covered the whole of the Earth's surface, and has been regarded as a single continent, called Pangea.
Fig. EP311-F1. Structure of the Earth. From .
Figure F1 is a representation of the main parts of the Earth's structure today. The main parts are the Core, the Mesolayer, the Mantle, and the Crust. The Crust is essentially re-worked material from the upper part of the Mantle, and as such, it contains all the varied rock types known to geologists. These include sedimentary, metamorphic, and igneous rocks -- essentially the results of weathering, sedimentation, and movements in upper parts of the Earth.
The modern Crust varies from about 40 km thick, down to nothing. Around 200 million years ago, there were no deep oceans, and the Crust covered virtually all the surface of a smaller Earth. There were only some shallow seas. This crustal rock surface must have been continuously stretched by expansion prior to Demi-Earth time, but it was only then that the crustal rocks were stretched apart enough to expose Mantle rocks.
How we came to understand Earth Expansion
Over recent years, the concept that the Earth has expanded in size over geological time has become more and more popular. There are now plenty of good, well-presented explanations for an expanding Earth. For example, as at the end of 2020, there were 34 videos up on YouTube about this topic. The basis of most of these is that the Earth has been expanding for most of its geological life -- some 4.7 billion years. This expansion has split apart the older continents, by inserting new sea-bed between them.
A detailed history of the scientific exposition of Earth Expansion is given in references [B] and [C] in the Stablemate Material section below, immediately preceding the general References section. Reference [A] in the same section explains how the Earth could undergo large changes in its volume and density, without any change in mass .
James Maxlow, the current doyen on Earth-expansion studies, has an extensive website on the topic , and published his latest book  in December 2021. On his website, James Maxlow shows a number of models of how Earth has expanded through the ages, from right back at the time of formation up to the present day.
Fig. EP311-F2. Expansion of the Earth, splitting the continents apart. From .
Figure F2 shows an extract from a YouTube video  on how the Pangaea of Demi-Earth times became split up into the modern continents by the insertion of new sea-bed. The idea that such a thing could happen is relatively recent. What settled the question for most scientists was the stunning evidence gathered from sea-floor probings during and after the so-called International Geophysical Year (which lasted from 1 July 1957 to 31 December 1958).
Multi-year programs involving ships drilling the deep ocean floors (Glomar Challenger, Joides Resolution), gradually exposed the whole histories of these sea-floors. The drilled rock contained minerals which could be used to date their times of formation. The complete picture which emerged was astonishing and unexpected. It turned out that all the deep ocean beds were made up of rocks younger than 200 million years -- they had all been formed during the Age of the Dinosaurs or subsequent to this. This unexpected data gave rise to an even greater puzzle -- where had the surface area occupied today by these deep seas come from?
Fig. EP311-F3. Ages of rocks on the ocean beds. From .
The conclusion is that 200 million years ago, the Earth was much smaller in diameter -- about half the present value. The Earth has been expanding, proving new surface area for the deep-sea basins. The subjects of Earth Expansion and Plate Tectonics are very extensive, for more detail, readers are referred to References [B] and [C] in the Stablemate Material references.
Look again at Figure F3, showing the ages of rocks on the ocean beds, and understand what this is telling us. The red and orange sections show sea-bed created during the last 30 or so million years, up to the present day. This new surface has been laid down on either side of mid-oceanic rifts, shown by the black lines. The most active areas have been the eastern Pacific, with a lot of new surface, and a large patch in the southern Indian Ocean curving around under Australia, as part of the Southern Ocean.
Another significant area, in the 0-30 million year range, has been created on either side of the Atlantic Rift, the double mountain chain running from north of Iceland right down to the southern Atlantic, where it merges into the Antarctic Ocean Ridge. This is all classical "sea-floor spreading", with molten rock emerging from volcanic slots and being pushed out on both sides by newly-emergent and younger rock.
The green, light-blue, and yellow areas show where sea-bed formation was most active in the first two-thirds of the 200-million-year period, while older rock, shown in blues and purples, is mostly along continental margins, but with a large area of its own in the Western Pacific. The age- and area-detail available makes it possible to trace the past history of any given part of the sea-bed quite closely, and the details are almost impossible to explain except by Earth Expansion.
The so-called Age of the Dinosaurs includes the Jurassic Period (201 to 145 million years ago) and the Cretaceous Period (145 to 66 million years ago). Figure F3 shows that the Earth added considerably to its surface area during these two periods, the addition all being new sea-floor.
How Demi-Earth was different: Part 1, GRAVITY
Conditions for life on Demi-Earth must have been different from those applying today. A prime example is Surface Gravity -- the gravitational pull felt by creatures on the surface of the Earth.
The laws of gravitation, developed by Isaac Newton in 1687, are well known. The gravitational force felt by an object on the surface of the Earth (usually called "g") is given by the formula F=G*M1*M2/D2, which just means it is proportional to the mass of the Earth, divided by the square of the distance to the centre. In everyday terms, this force has a value of 1g.
In a half-diameter Earth, the surface gravity would be 4g, four times the present value . This is basic physics, and no-one disputes the value. But we have plenty of fossil evidence from Demi-Earth times, with things such as dinosaur bones, and these just do not seem to fit the picture of a landscape where the gravity is four times as high as present.
This whole question has been detailed by Stephen Hurrell, in his book "Dinosaurs and the Expanding Earth" . He shows that dinosaurs, which included the largest land animals ever seen of Earth, do not have bone structures of the type needed to exist in 4g gravity, but instead were built as if they experienced much lower gravity than that of today's 1g.
Moreover he shows that some flying creatures of the times of the dinosaurs had greater wingspans than anything seen today, wingspans claimed to be "aerodynamically impossible" under today's conditions. He says that surface gravity in the past must have been considerably less than that known today.
How can these two conflicting points be reconciled? How could dinosaur bone structures cope with a gravity four times today's? The answer lies in the nature of Demi-Earth's atmosphere. If this was very much denser than that of today, its upthrust on the land creatures of Demi-Earth could counter the higher gravity.
Movement in a very dense atmosphere would become more like swimming. Creatures living wholly within the seas are not directly affected by the pressure of the atmosphere above the sea, but for land creatures in a very dense atmosphere, the float forces provided by the dense atmosphere would reduce the effects of gravity to a greater or lesser extent, depending on the density of that atmosphere.
I'll go on to show that Demi-Earth had an atmosphere was both very much denser and of different composition compared to that we observe today.
How Demi-Earth was different: Part 2, ATMOSPHERE
If the amount of atmosphere on DemiEarth was similar to that today, and was present on an Earth of half the diameter and a quarter the surface area, that would give an atmospheric pressure at the surface four times greater than today's, that is 4 atmospheres . If the mass of the atmosphere on Demi-Earth was much greater than today, as appears to be the case, then the surface atmospheric pressure would also be much greater.
To understand the atmosphere situation, we need to digress onto the composition of the atmospheres of Solar System planets and moons. These compositions are known to have altered fundamentally over the lifetimes of these objects.
Each planet or moon has what's called its Escape Velocity, which is more or less the minimum velocity at which an object must be fired upwards in order to escape the planet or moon. More massive planets. such as Jupiter or Uranus, have higher escape velocities, while smaller planets or moons, such as Pluto or Europa, have lower ones.
Fig. EP311-F4. Atmospheres of planets and moons in the Solar System. From .
An atmosphere is made up of gas molecules, which fly about and collide with each other continually, in what's called kinetic motion. For a given type of gas molecule, the higher the temperature, the more rapidly the molecules travel. When the average rate of kinetic motion of a molecule exceeds the escape velocity of a planet or moon, then that molecule may be lost into space.
In summary, what the Figure F4 graphic shows, is that heavier, colder planetary objects can retain much lighter molecules in their atmospheres than less massive, hotter objects. So the gas and ice giants of the Solar System (Jupiter, Saturn, Neptune, and Uranus) retain even the lightest molecules (hydrogen), while smaller planets and moons like Mercury and the Moon will lose almost everything they ever had in their atmospheres.
Fig. EP311-F5. Molecular Weights of some atmospheric gases. From .
The table in Figure F5 shows the molecular weights of some atmospheric gases. In general, planets and moons in space tend to lose all of their lighter gases progressively. Earth has lost all of its atmospheric hydrogen (MW=2) and methane (10) and kept a lot of its water vapour (18) and most of its nitrogen (28) and oxygen (32).
There are complications to this picture, for example Earth loses a lot of water vapour to space each year but picks up a lot of ice in its orbit to compensate , but these complications won't be gone into here.
The interesting part comes when we look at Venus, the next planet in towards the Sun. Venus is almost as heavy as Earth, but its temperature is quite a bit higher. Over the years, it has lost almost all of the gases in the table, except for the very heaviest, carbon dioxide (38).
In fact, the atmosphere of Venus is more than 96% carbon dioxide, with 3.5 % nitrogen, and fractions of one percent of carbon monoxide, argon, sulphur dioxide, and water vapour . But the big surprise with Venus is that its atmosphere is so thick -- about 90 times that of Earth, equal to a pressure of 90 atmospheres.
I will go into why the Venus atmosphere is so thick a little later, but the important point here is that it reflects directly on the atmospheric pressure which can be calculated for Demi-Earth. If, 200 million years ago, the Earth had a similar atmosphere to what Venus had now, but it was squeezed onto a planetary surface of one-quarter the area, the pressure on Demi-Earth would be 360 atmospheres (90 x 4).
This calculation can hardly be disputed. It is a simple multiplication of the atmospheric pressure on Venus today, by the surface area of the Earth today divided by its half-radius surface. Going back to the earlier suggestion that the dinosaurs could have body structures able to exist in a higher-gravity environment because of the upthrust of a thicker atmosphere, a pressure of 360 atmospheres would seem easily sufficient to supply the upthrust needed.
Why do the atmospheres of Earth and Venus differ so much?
The atmospheres of the "twin planets", Earth and Venus, are now very different. In earlier ages, the atmospheres of Earth and Venus were very similar. Subsequently there have been changes to both, but in different directions.
There is general agreement that Venus lost out because it is so much closer to the Sun and hotter, so that it could not retain liquid water and form seas. As a consequence, life like that on Earth never appeared, instead Venus just suffered physical changes in the gradual loss of all its lighter atmospheric gases.
On Earth, we know from dated sedimentary rocks that seas in some form appeared in the earliest days of our planet. We also know that eventually life appeared, and eventually life was responsible for fundamental changes in the composition of the atmosphere.
Earth's earliest atmosphere probably was mostly made up of methane and carbon dioxide, with some nitrogen and sulphur compounds. Primitive life extracted energy from reactions which gradually released free oxygen into the atmosphere. One of the biggest effects of this, well before the development of abundant macroscopic life in the Palaeozoic, was the oxidation of ferrous ions dissolved in the seas, giving the massive deposits of ferric iron rocks which are our current major source for steel and iron ores.
The Great Carbon Dioxide Draw Down
The time of Demi-Earth, 200 million years ago at the beginning of the Jurassic Period, saw the start of a period of huge draw-down of carbon dioxide from the atmosphere by plants and animals such as corals and shellfish, which continued throughout the Jurassic Period and the following Cretaceous Period. This carbon dioxide was converted into carbonate rocks which became part of the Crust.
Fig. EP311-F6. Geological Timecales. From .
These huge extractions of CO2 from the atmosphere, to make limestone and chalk deposits, totally changed the amount and composition of Earth's atmosphere during the Mesozoic Era. Carbon dioxide concentration was reduced from about 96% down to a fraction of 1% -- almost trace proportions -- where it has remained. Most of the carbon dioxide transformation was due to the action of life, particularly in formation of shells and bones.
Fig. EP311-F7. The Seven Sisters chalk cliffs in Sussex, England. From .
Figure F7 shows a small part of the extensive deposits of chalk (calcium carbonate rock), well known from the southern coast of Britain, as in the "White Cliffs of Dover". These were laid down during the Cretaceous Period as its signature component -- "cretaceous" means chalky. It's pertinent to ask, from where else could all this carbon be sourced, if not from the atmosphere?
There also appears to have been a draw-down of the second most common of the Venus-atmosphere components, which is nitrogen. The atmosphere of Venus actually contains about 4 times as much nitrogen as does that of Earth, suggesting that three-quarters of the original Earth nitrogen has been drawn down, again probably mostly through actions by life.
So the recipe for making an atmosphere like that of today's Earth appears to be: 1) Be further from the Sun, to retain water; 2) Use lifeforms to convert most atmospheric CO2 into carbonate rocks; 3) Use lifeforms to convert much of the atmospheric nitrogen to biological compounds.
More about the Demi-Earth Atmosphere
When compared to Earth, Venus has some major differences in kind, apart from its thick atmosphere. The first is that Venus is completely covered in cloud, at all times.
Permanent cloud cover leads to another factor -- little temperature variation. Unlike Earth, Venus has a single surface temperature, of 460 degrees Celsius, day or night, at the poles or at the equator . This is partly because the cloud cover evens conditions out over the planet's whole surface, and partly because the surface has a lot of mass above it, just as temperatures on Earth get more even with depth below ground. And as on Earth today, heavily overcast conditions go with lack of strong winds.
The suggestion that in Demi-Earth times our planet had permanent cloud cover over a dense atmosphere explains a number of puzzling observations. Dinosaur fossils have been found in what are now cooler areas of the Earth, as in southern Victoria . These dinosaurs are notable for their large eyes and apparent ability to cope with lower light conditions.
In recent years, more and more dinosaur fossils have been found in Antarctica , in areas with modern-day conditions far too cold for such creatures to have survived. It has often been remarked that the occurrence of the same fossils world-wide in rocks of the Paleozoic and Mesozoic means that conditions must have been much more uniform over the whole world then than they are now. This is true even if it is supposed that, say, fossils now found in the Arctic might have been moved up from warmer areas of origin by domain shifts, because there is no evidence of differing 'cold-weather' and 'warm-weather' fossils for those times, in contrast to modern flora and fauna .
The physical structures of ancient plants also suggest that they lived in atmospheres much denser than those applying today. The huge trees of Coal Measure times were apparently buoyed up by the dense air, since their cells were large water-filled sacs with comparatively thin walls, lacking the strength to stand up under today's conditions .
Finally, there is some direct evidence of higher atmospheric pressures in the Earth's history. Blobs of amber (fossilized tree sap) are sometimes found with small insects and other creatures trapped within them, sometimes perfectly preserved. Other blobs have small inclusions of gas within them, evidently tiny bubbles of ancient atmosphere. Carefully examined, these bubbles can be shown to be at high pressures, 10 atmospheres or more .
According to detailed Earth Expansion studies, at 200 million years before the present, the Earth had half its current diameter (Demi-Earth). Simple physics suggests that the surface gravity of the planet at that time was four times the current value (4g). However, examination of dinosaur bone structures suggest that they existed under a gravity of less than 1g. This conflict is resolved by analysis of atmospheric pressure on Demi-Earth, which is estimated at 360 atmospheres, enough to provide significant uplift countering high gravity.
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Stablemate material on the AOI website
[A]. EP314: How and why the Earth is Expanding.
[B]. EP302: The Earth-Expansion Model Part A: The Death of Plate Tectonics.
[C]. EP303: The Earth-Expansion Model Part B: Answers to A Hundred Puzzles.
References and Links
. David Noel. EP314: How and why the Earth is Expanding. http://aoi.com.au/EP/EP314.htm/ .
. James Maxlow. Beyond Plate Tectonics: Unsettling Settled Science. Terrella Press, 2021. ISBN: 9780992565213.
. James Maxlow. Website. www.expansiontectonics.com
. Rob Steenwinkel. Expanding Earth Theory. Video. https://www.youtube.com/playlist?list=PLEpr4aa9rk9r_AXSSUE1zL-6EhKB9OGaF .
. Seafloor spreading. https://en.wikipedia.org/wiki/Seafloor_spreading .
. Dinosaurs of the Frozen Continent.. Video, Blue Ant Media, 2021.
. Stephen Hurrell. Dinosaurs and the Expanding Earth. One Off Publishing, 2011, ISBN 0952260379.
. Atmospheric escape. https://en.wikipedia.org/wiki/Atmospheric_escape .
. Darin Dragozzine. Calculate surface gravity and atmospheric pressure on half-diameter Earth. http://assets.zombal.com/e9cca5c5/ZBL159Vault.pdf .
. The legend of carbon dioxide heaviness. https://www.researchgate.net/publication/228475055 .
. David Noel. EP307: Louis Frank Snowballs and Condensation of Interplanetary Matter. http://www.aoi.com.au/EP/EP307.htm/ .
. Nola Taylor Tillman. Venus' Atmosphere: Composition, Climate and Weather. https://www.space.com/18527-venus-atmosphere.html .
. Geological Time Scale. https://pcsstudies.com/geological-time-scale/
. White Cliffs of Dover. Video. https://flemingsbond.com/white-cliffs-of-dover/ .
. What is the Average Surface Temperature on Venus?. https://www.universetoday.com/14306/temperature-of-venus/ .
. David Noel. The Earth's Atmosphere [NU011]. http://aoi.com.au/NUSite/NU011.htm.
. Patricia Vickers-Rich. Big-Eyed Dinosaurs Foraged in Polar Australia’s Darkness. https://www.scientificamerican.com/article/big-eyed-dinosaurs-foraged-in-polar-australia-s-darkness/.
. John G Cramer. Dinosaur breath.. Analog Science Fiction/ Science Fact/ July p.140-143, 1988.
 David Noel. EP302: The Earth-Expansion Model Part A : The Death of Plate Tectonics. http://www.aoi.com.au/EP/EP302.htm .
 David Noel. EP303: The Earth-Expansion Model Part B: Answers to A Hundred Puzzles, http://www.aoi.com.au/EP/EP303.htm.
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Compilation started 2020 Nov 24. Draft worked on till 2020 Nov 29. Recommenced 2022 Apr 25. First version 1.0 on Web, 2022 May 3. Version 1.1, with input from Cliff Ollier, on Web 2022 May 11.