Guest “truth is stranger than friction” by David Middleton
Alternate Title: The Cretaceous Sea Level Paradox
Oceans are at their deepest in 250 million years
And they have hardly been deeper in the last 400 million years than now.Lasse Biørnstad
JOURNALIST
PUBLISHED Monday 08. june 2020 – 12:24
“It moves absurdly slowly,” says Krister Karlsen. He is a PhD candidate in Geophysics at the University of Oslo (UiO)’s Centre for Earth Evolution and Dynamics.Karlsen is talking about how the Earth’s tectonic plates move – ever so slowly but surely, every single year. From a human perspective, this happens so slowly that it is almost imperceptible.
[…]
The world map 200 million years ago shows all the continents assembled in the supercontinent of Pangaea, a time when dinosaurs were well on their way to dominating the Earth’s landmasses.
Since then, the continents have been shifting farther and farther apart, and now they may be as far apart as they can be, says Karlsen. Give the Earth a few hundred million years more, and the continents will probably remerge into a new supercontinent. One proposed name for that possible future reunion is Pangaea Proxima, according to New Scientist.
The movements and age of tectonic plates have a great effect on the depth of the world’s oceans. Just over 100 million years ago, the oceans were around 250 metres shallower on average than they are today.
The older the seabed, the deeper it is, according to a new research article by Karlsen and several colleagues at the Centre for Earth’s Evolution and Dynamics.
[…]
Science Norway
Karlsen et al., 2020 is essentially a reconstruction of plate tectonics and the age of the oceanic crust over time.
According to their reconstruction (and others), 100 million years ago, during the middle of the Cretaceous Period, the oceans were about 250 meters shallower than they are today *and* sea level was about 250 meters higher than it is today. Process that for a moment… The oceans were 250 meters shallower, but the water level was 250 meters higher than it is today. This was due to the geometry and distribution of the ocean basins. While advancing and retreating ice sheets may have played a role in Cretaceous marine transgressions and regressions, the Cretaceous sea level paradox was a tectonic feature and a boon to humanity.
During the Mid-Cretaceous, shallow seas covered many continental interiors…
While the ocean basins were, on average, considerably shallower than they are today.
“How about that, geology fans?”
Apollo 15 CapCom Joe Allen on Dave Scott’s discovery of the “Genesis Rock.”
References
Goswami, A.; Hinnov, L.; Gnanadesikan, A.; Young, T. Realistic Paleobathymetry of the Cenomanian–Turonian (94 Ma) Boundary Global Ocean. Geosciences 2018, 8, 21.
Karlsen, Krister S., Mathew Domeier, Carmen Gaina, Clinton P. Conrad,
A tracer-based algorithm for automatic generation of seafloor age grids from plate tectonic reconstructions, Computers & Geosciences, Volume 140, 2020, 104508, ISSN 0098-3004, https://doi.org/10.1016/j.cageo.2020.104508.
As I read the post, the “thickness” of the oceans has increased by 250 meters during the last 100 million years to where it is today. Consider the volume of water this represents. And this decreased “thickness” of the oceans occurred during the middle of the Cretaceous period, when temperatures were much warmer and probably little to no ice present at either pole. Expansion would have been much higher during the Cretaceous period as well.
I don’t think the total volume of water that has existed since water formed, has changed that much. Where was this volume of water (represented by 250 meters “thickness” covering 3/5 of the surface of the Earth) hiding during the Cretaceous period?
What was the original composition of Earth’s atmosphere 1,500 Ma before life forms?
I had once read that the atmosphere was MAJORITY N/CO2 and the sky appeared pink . . . instead of blue due to O2.
Can someone point me to a source?
Thanks.
Atmospheric composition…lots of carbon dioxide, nitrogen, a smidgen of methane, ammonia and carbon monoxide, possibly hydrogen and a slight, very slight, trickle of oxygen’
https://advances.sciencemag.org/content/6/9/eaax1420
Sky colour….probably pale orange
http://www.travelinggeologist.com/2018/06/how-planet-earth-became-a-pale-blue-dot-with-janne-liebmann/
I once did a thought experiment … really as the basis for a never-written sci-fi novel.
Explorers coming back to the Earth in it’s last days, about 5B years in the future, on it’s way to becoming a red giant, expanded to roughly the orbit of Venus.
The earth at that point is tectonicly dead. The continents have all eroded away.
The Earth is now covered with water – about 6′ deep. Probably tidally locked, so currents keeping the dark side warm to radiate away the hear from the huge red sun dominating the sky.
Since then, I would have to add a more or less permanent line of thunderstorms (thanks Willis!).
So … maybe the seas are getting deeper right now. I see them (in my imagination) getting a lot shallower in the distant future.
The whole topic of continental drift/ocean floor spreading etc is geologically immature, in the earliest stages of investigation. If an author wants to extend study into ocean water depths and heights, the uncertainties of plate tectonics carry over into such study and make meaningful deductions almost impossible.
Some teasers have already been raised here, like where the energy to move plates comes from. Another teaser looks at geological times older than about 500 million years. That is about the metamorphic age of spread floor at its outer boundaries. Question: what processes were at work before then, during the massively greater earlier times, when helps like magnetic stripes are gone? What did ocean depths and heights do then? Another teaser, what does one use as an ancient reference level against which to measure vertical movement? Another, how does one measure the historic quantities of water of crystallisation in metamorphic rocks and consequent variations in free water volume? One can go on for hours of pointless conjecture. For what gain?
Another big question: apart from the valid scientific drive to complete global jigsaws, why are researchers publishing papers like this one, with possibly intended implications for climate change policies, when the uncertainties are so huge? Surely the vast majority of planning for ocean level changes can be measured with adequate accuracy and projected with high confidence, from the many tide gauges with century-long records. What more data do we need for most of our future planning?
It is tiresome to read paper after paper based on conjecture and arm waving by often junior authors who seem desperate to find something, anything, to subvert the plain but inconvenient evidence from the tide gauges, nasty devices that refuse to yield alarming numbers. Geoff S
Why are you all discussing this ludicrous article? You are like nerds discussing Star Wars as though it is real. To those who laugh at this shit, thank you, it makes me feel a little better about humanity and to those who give it a moments credence….sad.
Similar question to some posed above:
if the diameter of the earth was the same in the Cretaceous 100my ago as it is today, and all the current continents were not broken up and still part of a whole Pangea, would they not all be congregated on one side of the earth, with the rest as ocean?
Big problem for rotational/orbital stability?
From the sun’s point of view, the earth’s equator (roughly) passes by at a rate of 1000 MPH. The poles at 0 mph. That means one hell of a lot of centrifugal force from inside the earth to the surface, (not just coreolis), forcing the equatorial areas to be bulged out. The result is called an oblate spheroid, and it means the poles are flattened and the center is bulged. It doesn’t take much imagination to figure out why it is that shape. Imagine a spinning top with flexible ‘skin’.
The continents NOT responding to these forces is what is unimaginable. It is as if earth is trying to ‘fling’ the center continents off the earth. Not the most scientific example, but hopefully, it is an example of common sense about what must be at work here.
Just how do you imagine the continents would be “affected” by this centrifugal force?
A slight tug towards the equator?
I would say the opposite – away from the equator. If I were to image the long term land mass arrangement, I would expect there to be continents around the poles, and nothing in the center, eventually. The atlantic spreading could very well be due to the centrifugal forces. But the most massive force is at the center of rotation.
As always, Dave, your mini-geology lessons are both informative & fun. Keep ’em coming!
Cheers — Pete Tillman
Somewhat off-topic, but does anyone know why the University of Colorado have not updated their SLR graphs since Feb 2018?
http://sealevel.colorado.edu/
Apologies if I’ve missed a past WUWT post on this, but a quick search didn’t turn anything up.
“truth is stranger than friction”
Shouldn’t that be fiction?
Not in my world… 😉