Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: meems on 29/11/2017 20:08:05
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hi. I'd like to know if there has been any in-situ measurements of mid ocean rift rates. Like some locators dropped onto the ocean floor near and either side of the rift, and a method employed to discern their distances over years, which should increase by a few cm per year.
I've always assumed this simple and obvious experiment would have been done and repeated many times, such that today after more than 50 years after the discovery of mid ocean rifts, there'd be a network of locators along mid ocean rifts all working to measure the rift rate. I've been searching myself for any papers on this subject but in all my time I've found none.
Perhaps I'm unskilled at finding papers. Does anyone know of this experiment or the group that manage the mid ocean rift locator network?
thx
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When I google search, I find numerous reports about probes sent to the mid ocean ridges : to measure the outflowing water temperature, chemistry, biology and ecology. We're sending a lot of probes to the mid ocean rifts. Makes it all the more baffling why I cant find reports on in-situ rift rate measurements.
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locators dropped onto the ocean floor near and either side of the rift, and a method employed to discern their distances over years, which should increase by a few cm per year.
That is the crux of the problem, how would you measure that small movement.
On the surface laser triangulation can take accurate measurement, but at depth the measurement is extremely difficult. Most surveys rely on seismic imaging and core sampling.
Look at this link which will give you some names to search on or contact. https://www.ldeo.columbia.edu/~polsen/nbcp/basinevolution.html
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I'd think sonar or some EM frequency could be used to coordinate. If directline of sight is needed, a tripod or quadpod stand could be used. Other methods, a cable from one locator to another.
EM triangulation can have a resolution of nanometres, we only need mm to get started here.
Your reply suggests indeed there is no direct measurement of constructive rifting!
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Your reply suggests indeed there is no direct measurement of constructive rifting!
I didn’t say that, I said it was not straightforward. Systems do exist but because of complexity and cost are not used as first line investigation.
I've always assumed this simple and obvious experiment would have been done and repeated many times, such that today after more than 50 years after the discovery of mid ocean rifts, there'd be a network of locators along mid ocean rifts all working to measure the rift rate.
Placing sensors is expensive and only measures drift (plus temperature which is useful for oceanographich info), so for slow movement you get a lot more info about long term trends plus geology by using seismic and core drilling techniques, so it isn't worth putting blanket sensors out.
Where there is significant drift it is worth real time monitoring for example in this rift which is moving at 65mm/yr and represents a significant seismic risk:
https://www.sonardyne.com/case-study-long-endurance-monitoring-tectonic-motion/
The other article I posted gives you a starter for your search linking to experts in the field.
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The easiest place to measure this divergence is in Iceland, where the mid-atlantic ridge rises above sea-level.
There is a rift valley here that started opening in 1789.
There are major earthquakes about every 10 years, so the rate of divergence may not be uniform on timescales of 1 year.
See: https://en.wikipedia.org/wiki/Silfra