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The spread of the oceans’ sea floors appears to be slowing

The uncertainty of science: Based on data covering the last 19 million years, scientists now believe that the rate in which the Earth’s ocean sea floors are spreading has been slowing steadily.

Today, spreading rates top out around 140 millimeters per year, but peaked around 200 millimeters per year just 15 million years ago in some places, according to the new study. The study was published in the AGU journal Geophysical Research Letters, which publishes high-impact, short-format reports with immediate implications spanning all Earth and space sciences.

The slowdown is a global average, the result of varying spreading rates from ridge to ridge. The study examined 18 ridges, but took a particularly close look at the eastern Pacific, home to some of the globe’s fastest spreading ridges. Because these slowed greatly, some by nearly 100 millimeters per year slower compared to 19 million years ago, they dragged down the world’s average spreading rates.

You can read the actual paper here.

To put it mildly, the conclusion here is uncertain. The difference between 140 and 200 millimeters is less than two and a half inches. A hundred millimeters is less than four inches. Such small differences over millions of years could simple be caused by random fluctuations over time. Furthermore, the scientists did not actually detect the spreading rates from millions of years ago. They instead inferred it based on the data we do have of the changes in the Earth’s magnetic field over time.

Still, this result is very intriguing indeed. More than anything, it should help geologists develop better theories to explain plate tectonics, and what drives it. At the moment no theory adequate explains it.

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  • Gary

    Obviously, it’s caused by the increase in carbon dioxide in the atmosphere from burning hydrocarbons for evergy. /Sarcasm off

  • Alex Andrite

    /sarc on.
    Gary, it is because of all the people and industries leaving California. JB knows this and is using the open border to repopulate CA to re-balance the pacific plate. Titled the teeter-totter effect.
    Now back to our recess.

  • sippin_bourbon

    Blame Bush.. er wait.. that’s old.. um… Blame Russia.

    Checks notes.. Blame Musk. It all started when he bought twitter.
    (I say this all with sarcasm.. but give it 6 months).

  • Edward

    Gary and Alex Andrite,
    I’m pretty sure it is all Orange Man Bad’s fault, and was bush’s fault a decade ago. Either way, it is the coming ice age/global warming/climate change/climate weirding/etc. Which is all Orange Man Bad’s fault, and was bush’s fault before that.

  • pzatchok

    This all because of global warming.

    It all started when apes first started walking upright.

  • Chris

    I want to see the ocean sized caliper they measured with.

  • MichiCanuck

    The geomagnetic reversal time scale, which shows up as magnetic anomaly stipes in oceanic crust is quite well established by a huge number of radiometric dates. The basics were worked out in the 60s and 70s. The actual spreading rates are measured in terms of kilometers per million years. A 1 cm per year rate equals 10 km per Myr. People are not measuring millimeters of spread, although the current spreading of the Atlantic Ocean has, I recall, been confirmed by long term precision GPS measurements. I think that the individual spreading rates as a function of time will be quite well determined, certainly to a precision better than the ~30% difference claimed in your quote. The tricky aspect will be the combination of spreading rates around the globe. There’s a lot of complicated geometry involved and not all ocean ridge systems are likely to be equally understood. However, the important thing to note is that reversals (which happen roughly 0.5 to 1 Myr apart, the last being ~780 kyr ago) are well documented and show up as magnetic stripes spanning many kilometers. Distances like that can easily be measured, even by rocket scientists. :-)

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