V-Shaped Ridges This image shows the bathymetry of the ocean floor just south of Iceland (reflected

V-Shaped RidgesThis image shows the bathymetry of the ocean floor just south of Iceland (reflected through the gravity), an area with a remarkable feature. See how there are linear features elevated above the surrounding ocean floor that open to the North? These are known as the V-shaped ridges and they demonstrate a remarkable property of the Icelandic plume.Iceland is a unique spot on earth, a combination of a mantle plume and a mid-ocean ridge. The mantle plume carries hot material in the mantle up from deep, causing Iceland to rise above the ocean floor as a huge island. The mid-ocean ridge south of Iceland shows some influence of this plume, changing in composition and rising higher above the ocean floor than ridges elsewhere in the world.The V-shaped ridges are formed at the mid-Atlantic spreading center. They’re elevated because they’re thicker, so they’re probably produced by melting of extra- hot mantle, like Iceland but not to the same extreme.The real interesting feature from a geophysical perspective is the shape. The mid-Atlantic ridge keeps spreading at a constant rate regardless of what is happening along this ridge, so to produce a V-shape, a blob of mantle that produces extra melt has to actually migrate away from Iceland.To make this ridge, a blob of extra hot mantle rises up south of Iceland and then flows away, being sampled along the ridge as it moves. This pattern of alternating ridges and valleys therefore tells us that whatever it is that drives volcanism in Iceland…it actually occurs in pulses!A pulse of mantle that melts extra rises up beneath Iceland and migrates away down the Mid Atlantic ridge. The ridge pushes the rocks apart, making a V-shape out of that ridge, while another pulse forms near Iceland and begins moving its way to the south.-JBBImage credit: http://www.nature.com/nature/journal/v411/n6838/images/411681aa.2.jpgRead more: http://onlinelibrary.wiley.com/doi/10.1029/2002GC000361/abstract -- source link

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