Nature

Africa splitting is just the beginning, Earth’s undergoing massive changes


Compared to our knowledge of other rocky worlds in our Solar System, our planet is an incredibly dynamic one.

Water in its various states weathers, erodes, and builds anew. Beneath our feet a slowly churning mantle grinds and spews rock.

 

The changes rendered by geological and meteorological processes are so gradual, it’s easy to think our planet will always look like this.

Hints of the face of future Earth are there, though, if you know where to look.

As solid as the ground might feel beneath our feet, most of our planet’s dry land is made up of moderately buoyant plates of mineral pushed around by the churning of a thick layer of molten rock.

So slow is this dance, nobody really noticed it was even happening until a geophysicist named Alfred Wegener pointed out in 1912 that this could explain why similar fossils and rock formations are divided up across the four corners of the globe.

Since then we’ve seen the signs of how this powerful force will continue to shape arrange our continents.

Africa is splitting in two

Just as Africa divorced South America millions of years ago, Africa is itself now splitting in two.

A giant crack in south-western Kenya that is visibly breaking apart the landscape, severing a major highway, points to this split that will see the continent divide apart.

 

It’s a small indication of a drift that moves just a few centimetres each year. Tiny, but one that suggests in 10 million years the east African plate of Somali will be isolated by ocean, and in 50 million years Africa’s bulk will have pushed into Europe.

Roughly 300 to 180 million years ago, all of the continental plates were piled together in what was called Pangaea.

Current predictions see all of the continents will squish together again in about 250 million years.

Tides could change dramatically

This cycle of break-ups and reformations has an interesting effect on the Sun’s and Moon’s influence over the oceans.

The monthly ebb and flow of tides we’re used to seeing can only occur when there are sizeable basins of water. 

Computer models suggest over the past quarter of a billion years, tides might have been a lot weaker. It’s only for the past two million years that we’ve see such ‘supertides’ washing over our globe.

That just might mean as the continents continue to shift, those basins might change shape again in the next hundred or so million years, once again interfering with tidal activities.

 

Australia is moving north too quickly for GPS to keep up

On a far smaller time frame, movements in the distribution of our planet’s water can in turn have a strange effect on how our continents move.

Seasonal changes to this aquatic map make a slight difference to how tectonic plates move, quite literally ‘sloshing’ them around. Australia is shaking back and forth on a scale of millimetres as it makes its way north.

While this wobble is trivial over large scales, it could make a huge difference where tiny measurements count.

Forget millions of years in the future – in just a few years, it might push Global Positioning Satellite (GPS) estimates out by a significant amount.

In a world where we’re increasingly reliant on mapping technology, this small change to the face of our planet might be a serious issue.

Ice is becoming ocean – very heavy ocean

Another incremental shifting in the crust’s position is being caused by changes in the distribution of water from ice to ocean.

Last year scientists from NASA’s Jet Propulsion Laboratory in California reported on a wave made up of 6.68 billion tonnes of frozen water inching its way down a glacier in Greenland in 2012.

 

This snail-paced tsunami literally warped the crust as it passed, demonstrating the impact all of that water has on the shape of our planet.

This wave is barely a ripple compared with the compression the ocean floor is under; we’re only just starting to comprehend how rising sea levels will push back down on the crust, bending it out of shape on a far larger scale.

The scars left by grinding rivers of ice during the last great ice age are clear across much of the globe, and as glaciers continue to melt we’ll no doubt be left with a similarly marked landscape.

Yet they do more than gouge valleys from the rock and push down the crust – huge piles of sediment called eskers accumulate at the glacier’s mouth, perforating the belly of the ice flow as it reaches the sea.

Researchers recently discovered knife-like eskers in Antarctica the size of the Eiffel tower. These build ups weakening the ice shelf, giving us one more thing to worry about as Antarctica’s ice cap slowly degrades and adds to rising sea levels that will also remap the globe.

It’s barely been a century since we started to fully appreciate the dynamic nature of our planet’s face. If recent science is anything to go by, we still have so much to discover.  

 



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