Large crack in East African Rift is evidence of continent splitting in two | Hacker News Reader

Large crack in East African Rift is evidence of continent splitting in two

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148 pointslovelearning49 comments

Wild eyed idea. Could we run a cable across this. Have it turn a gear. Then gear it up to a one million to one ratio and turn a giant generator with the motion?

Free continental drift power?

Something with that much gear ratio would essentially be locked. It would most likely just tear the mechanism apart before it did any actual work.

Then a thousands of them over the split with a thousands less ratio :P

Considering the drift is occurring at a rate of a couple millimetres a year...no.

With high enough gearing that is plenty. The issue is we are not capable of building strong enough gears.

Seems like someone already had that idea, atleast for the continental shelf: https://patents.google.com/patent/US8258638

I love this idea, but the speed of separation is just a couple of cm per year. Unless the cable had absolutely no temperature expansion, weather changes would probably have a far greater effect on cable length than the imperceptible drift of the endpoints (which suggests another crazy idea interesting in its own right).

One might build this deep underground to minimize temperature changes and provide the hard rock anchor points necessary for the forces involved.

Go deep enough and you might as well just build a geothermal power plant.

Which would have the side effect of actually generating power!

Kenya is way ahead of you:

https://www.nytimes.com/2018/02/23/business/geothermal-energ...

Kenya generates 47% of power from geothermal and 35% from hydro. For a third world country, it’s quite greener than most developed nations. https://mobile.nytimes.com/2018/02/23/business/geothermal-en...

I do hope Kenya gets a electric car boom, because all of it’s fuel is imported. Solar + other methods could power the whole economy with relative ease. Being on equator means plenty of sun throughout the year.

> weather changes would probably have a far greater effect on cable length than the imperceptible drift of the endpoints (which suggests another crazy idea interesting in its own right)

There is a clock running for over a century based on a similar idea: https://en.wikipedia.org/wiki/Beverly_Clock

...and the commercial version, which is still in production:

https://en.wikipedia.org/wiki/Atmos_clock

Not cheap (few k$), but not as expensive as some other high-end timepieces either.

> Unless the cable had absolutely no temperature expansion...

One might be able to get a composite with very close to zero thermal expansion coefficient by linking stages made of materials with positive and negative [1] coefficients.

[1] https://en.wikipedia.org/wiki/Negative_thermal_expansion

You don't even need to use exotic materials with negative thermal expansion: instead, you can use a combination of materials with different coefficients of thermal expansion pointed in opposite directions. This was one of the innovations that John Harrison made that allowed him to make precision timepieces.

https://en.wikipedia.org/wiki/Gridiron_pendulum

You could use a couple of anchors so that when it only moves 1mm the end attached to the gear would move several meters. Where the gear is really huge which makes the small gear spin faster. But it might still be too slow.

You'd stand a better chance to get that to work by using hydraulic pistons that are used to compress a working fluid using an appropriately placed lever.

There’s lots of other ‘free’ and ‘infinite’ energy around that is much easier to collect. You could go to the moon and make strawberry jam and then market it as ‘Space Jam’ but it’s simpler and cheaper to skip the whole moon part.

lemonde.fr published an article [1] yesterday, in which they debunk this news. A seismologist at Southampton University says [2] that it's unrelated to the rifting.

[1] https://www.youtube.com/watch?v=4QJ8MmbAC_o (in French)

[2] https://twitter.com/seismo_steve/status/977258571716091904

Lots of people don’t realize that North America almost did this same thing about a billion years ago. Check out the failed rift zone called the Midcontinent Rift. Ever curious why Lake Superior is shaped like that? MCR ground zero.

https://en.m.wikipedia.org/wiki/Midcontinent_Rift_System

What about how Lake Superior is shaped indicates anything weird is going on?

Does this also explain the extended butte-and-valley terrain in the Southwest?

The butte-and-valley terrain, as you called it, is more from the uplift and slow erosion of a large area called the Colorado Plateau. The various sediments deposited on and off over a billion years or so have different erosion rates. When a thick, more weatherproof, sandstone overlies a more erodable shale you get those big cliffs and buttes.

The area covered by Nevada, on the other hand, is being pulled apart over the whole state. This creates what is called a basin and range topography. The extension is mostly east-west and you can see the ranges and valleys mostly are north-south due to this. Lots of geothermal there as the spreading rock allows hot rock from below to move close to the surface.

I was also going to mention that.

Also, it displays the same equiangular vertex of three rifts that we see with the Arabian, Nubian and Somalian plates. Which you also see in oxide scum on molten lead. Or on oatmeal, just before it's ready.

Non-mobile link https://en.wikipedia.org/wiki/Midcontinent_Rift_System

Does anyone else think this is just erosion in the soil due to heavy rain? That's probably too boring of a story though. I think an earthquake that pulled the land apart that wide would be a major news event.

Seems very plausible. Roads in my area are currently full of wide cracks and holes that appeared seemingly overnight, as happens every spring.

It's not evidence of continent splitting but of soil erosion, much like what is happening in Rome[0]

[0](http://www.lastampa.it/2018/02/14/italia/cronache/roma-si-ap...)

Probably not...

> and was accompanied by seismic activity in the area.

Was this a sudden shift of several feet on the ground level (because the underlying ground was in tension for years)? Or how does a crack that big form? Is it even as big as the hole? I.e. if we were to measure from two points across the crack - did they move as much as the crack is wide?

Who would own the new land?

"the South Atlantic ocean, which resulted from the break up of South America and Africa around 138m years ago – ever noticed how their coastlines match like pieces of the same puzzle?"

No I had not but now that I look at it it's so obvious. And wow!

Alfred Wegener noticed this about a hundred years ago and formulated that theory around this observation and some supporting evidence. However, until the 1950s and 1960s the why would they be moving? was wholly unanswered and Wegeners theories were not accepted until then.

It's remarkable how young that understanding is

They match, but only at a curvature slightly smaller than the Earth's curvature, spawning many theories about an expanding Earth in the early days of geology. Those theories have all now been debunked but they make for a fascinating read if you're into scientific rabbit holes.

Also the North Atlantic, but less clearly. Also Greenland and northeastern Canada. And Greenland and Norway, I think.

One related fact that I love is that the Congo and the Amazon used to be the same river - the Amazon reversing flow when the Andes rose up:

https://en.wikipedia.org/wiki/List_of_rivers_by_age

If it's rift due to plate separation, wouldn't the crack go down all the way to the mantle? Not the 20-30 feet seen in the video.

It does, but in general when a rupture opens up at the surface, the side walls fail quickly and fill it in with loose material. It is only when a surface rupture is "fresh" that it looks as dramatic as this.

Sure, the side walls fall in... but wouldn't that happen more easily near the surface, with loose topsoil, than for deeper rock? Meaning, that if the top part hadn't fallen in yet, the lower parts wouldn't have either.

Perhaps pressure with depth is a factor, tending to press the sides together. Amd the deeper material might not be rock, but e.g. sand or other loose material.

There isn't just one well-defined crack. Where the plates are separating there is a whole zone of material that is being pulled apart and cracking open. The current crack is just one of many many fissures in the rift zone. And the individual fissures are jagged and ziggy-zaggy, so even if they had clean sidewalls you still couldn't see straight down to the bottom.

Also, the crack is not filled in all the way to (near) the top. There are gaps and voids all the way down. The "bottom" that you see is just the first filled-in part. If you dug down you'd probably find more gaps. (I'm not 100% sure about this. I know about the mechanics of slip-strike faults because I live in California within walking distance of the San Andreas, but the African rift is different so I could be wrong about some of these details.)

This well known process, which will play out over tens of millions of years, appears to be receiving media attention because ...

> A large crack, stretching several kilometres, made a sudden appearance recently in south-western Kenya. The tear, which continues to grow, caused part of the Nairobi-Narok highway to collapse and was accompanied by seismic activity in the area.

That's literally the title of the article.

If it hadn't gone through the highway, I doubt there would have been the flurry of "Africa splitting in two!" articles.

No-one's allowing East-Africa its 15 million years of fame...

I am imagining the copywriter fighting the urge to say "there's a rift in the Rift."

There was a previous flurry of media attention about the extreme geology in Djibouti and Ethiopia.

https://www.theguardian.com/world/2006/nov/02/travelnews.tra...

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