https://www.livescience.com/65016-imposs...sland.html
On a tiny island between Madagascar and the east coast of Africa, scientists have discovered a mother lode of rocks that shouldn't be there.
The island is made from igneous, volcanic rock that hails from the oceanic crust. But the mystery rocks come from continental crust — more specifically, from a river delta or beach.
Since at least the 1900s, geologists have reported finding some very nonvolcanic rocks on Anjouan. In the 1980s, a French team documented some scattered outcroppings of quartzite. In 1991, Class saw a few pieces herself while working on her doctoral research on the islands.
Quartzite simply shouldn't be on Anjouan. The island sits in an ocean basin. Such basins form as tectonic plates pull apart, allowing magma from the mantle to roil up, harden and form new crust. Due to this process, Class said, the rocks from ocean basins are basaltic: dark, magnesium- and iron-rich rocks of the sort that make up the Hawaiian Islands or the iconic outcrops of Devils Postpile in California.
Continental plates, on the other hand, are made of less-dense, lighter-colored granitic rocks. Transition zones between oceanic and continental crust can hold both types of rock, but Anjouan doesn't match those regions.
Okay - so, small quantities of this "quartzite" rock was first discovered on the island in the 1980s; however, this is the first time half a mountain of the stuff has been discovered. Our current theories suggest it shouldn't be present in an ocean basin - so, how did it get there?
I will admit, I'm less than impressed by the sources available on this story so far: they go back to this blog post, rather than an academic journal. Furthermore, Live Science isn't the best source out there, but the few articles I could find on other outlets either link back to Live Science or the blog post . Still, assuming that there is anything to this, I will be intrigued to find out more!
On a tiny island between Madagascar and the east coast of Africa, scientists have discovered a mother lode of rocks that shouldn't be there.
The island is made from igneous, volcanic rock that hails from the oceanic crust. But the mystery rocks come from continental crust — more specifically, from a river delta or beach.
Since at least the 1900s, geologists have reported finding some very nonvolcanic rocks on Anjouan. In the 1980s, a French team documented some scattered outcroppings of quartzite. In 1991, Class saw a few pieces herself while working on her doctoral research on the islands.
Quartzite simply shouldn't be on Anjouan. The island sits in an ocean basin. Such basins form as tectonic plates pull apart, allowing magma from the mantle to roil up, harden and form new crust. Due to this process, Class said, the rocks from ocean basins are basaltic: dark, magnesium- and iron-rich rocks of the sort that make up the Hawaiian Islands or the iconic outcrops of Devils Postpile in California.
Continental plates, on the other hand, are made of less-dense, lighter-colored granitic rocks. Transition zones between oceanic and continental crust can hold both types of rock, but Anjouan doesn't match those regions.
Okay - so, small quantities of this "quartzite" rock was first discovered on the island in the 1980s; however, this is the first time half a mountain of the stuff has been discovered. Our current theories suggest it shouldn't be present in an ocean basin - so, how did it get there?
I will admit, I'm less than impressed by the sources available on this story so far: they go back to this blog post, rather than an academic journal. Furthermore, Live Science isn't the best source out there, but the few articles I could find on other outlets either link back to Live Science or the blog post . Still, assuming that there is anything to this, I will be intrigued to find out more!
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