Thursday, 25 October 2012

The Marvellous Granites of Seychelles


The Seychelles are the only granitic oceanic islands in the World. Formed millions years ago, the size and shapes of some of these granites are truly mindboggling. TONY MATHIOT tells us about a few of them.

ANSE L’UNION GRANITE BOULDER (at Anse L’Union, La Digue)

Granite. Our glorious granite. Forty islands in the Seychelles archipelago are granitic. The fascination of the Seychelles lies not only in its resplendent greenery or in its pristine beaches or sunshine. The granite is awesome. Majestic. One admires and gasps. Yes, it’s PLUTONIC! But can one go dithyrambic over the granites of Seychelles without venturing into the recondite science of geology stratigraphy or Petrogeny?!

The granites of Seychelles date back to millions of years ago to the Mesozoic era… to the time of Gondwanaland, the time of the first amphibians, the first winged insects, the first dinosaurs.

Granite is an igneous rock that formed by solidification from a molten state (igneous comes from the Latin word ignis: to inflame). It is made up mainly of crystals of quartz, feldspar and mica. And it was formed deep in the earth. And while the magma, that is, the molten matter, was forming, fragments of materials called xenoliths were trapped in the magma before it crystalised – yes, like dust of glitter in a bath of hot treacle!

Since granite was formed deep beneath the earth’s crust, it is because the rocks lying on top of it have been worn away or because it has been pushed upwards by movements of the rocks long ago.

Yes, long ago. And now when one beholds this grandest scenery of granite covering over one acre of land, here on the west coast of La Digue, it is almost stupefying to realize that we are the only oceanic granite islands in the world.



ROS KOSON (at Anse Louis)

On the beautiful west coast of Mahé, one finds this marvelous monstrosity! A veritable natural wonder! Yes, this is Ros Koson (Pig rock) aptly named because it certainly resembles a crouching snarling hog in profile. One can distinctively make out the sunken eyes, the cartilaginous snout over the mouth baring the teeth in a rictus of rage. Definitely one of our most common ungulate mammals!

Of course with so much granite around, it is not uncommon nor unusual to come across boulders or shapes of some recognizable representation.

But upon seeing this particular ‘pig’ up there, one is naturally inclined to wonder just how long has it been perched up there on that giant boulder?

We’ve been told by scientists that once upon a time, meaning so many millions of years ago when all continents were joined that Seychelles, a tiny fragment of the earths crust halfway between Africa and India became isolated during the so-called continental drift… could that rock have landed up there on that boulder during the upheaval and then over the centuries it was shaped into a pig by the ravages of time? Fascinating!

One thing for sure. This is one pet porky that future inhabitants of Anse Louis will certainly inherit and learn to like!.


ROS LESKALYE (ROCK STEPS) (at Port Launay)

The resplendence of Port Launay in North Western Mahé is breathtaking. Here along the boulder-strewn coast the waves of the Indian Ocean come to nudge themselves against the rocks after having spent their rage further away. But amidst this sublime scenery there is a particular feature that certainly can be baffling to the lonely peasant who happens to venture along this part on an afternoon when looking for limpets (bernik).
These steps are mind-boggling. Almost like a gateway to the backwoods used by undersea aliens! Fascinating! Well, geology IS fascinating.
This rather unusual feature is known as a dyke. It is typically the result of igneous intrusion: a long mass of igneous rock that cuts across the structure of adjacent rock. This happens when magma or molten rock move upwards by injecting into cracks at higher levels in the earth’s crust, forcing the sides apart. Magma solidifies in the crack to form a dyke, and in the case here at Port Launay, the dyke do look like a row of steps.

MIRAY DEMON (at Anse Déjeuner)
Miray demon? (the devils wall?) Why on earth would he build a wall here on earth in Paradise?!

Yes, this is certainly a mind-boggling sight. One gets the impression that these different sizes and shapes of granite boulders have been gingerly arranged to rest on top of one another to make a crude wall.

Well, some inhabitant of Anse Déjeuner must have appreciated the extraordinary strength of the devil and gave this bizarre heap of boulders an appropriate appellation!

In fact, once upon a time, a long long time ago, this was one single huge boulder. The ravages of time which spanned thousands of years, created fissures and clefts in it and gradually it was divided into separate pieces of rock which have more less remained in place like interlocking pieces of a gigantic jigsaw puzzle. That’s the mystery of the devil’s wall… For sure, those boulders will never be taken to the crushing plant located a mile away to be turned into aggregate!

Article first appeared on Virtual Seychelles. Original article can be found here: http://www.virtualseychelles.sc/index.php?option=com_content&view=article&id=842:the-marvellous-granites-of-seychelles&catid=51:additions

 

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