Iceland’s Volcano Spews Unusual, Continental Rock

AMHERST, Mass. – Iceland is the only place on Earth where land sits atop a mid-ocean spreading center, says Sheila Seaman, professor of geosciences at the University of Massachusetts Amherst. One aspect of Iceland’s volcanoes of particular interest to geoscientists is that within the magmas being extruded there are small amounts of lightweight, light-colored volcanic materials known as felsic rock, which “has no reason whatsoever for being there – it’s the kind of stuff found in continental crust, not ocean crust,” Seaman says.

So Iceland is an area of real scientific questions and potential discovery about the origin of both ocean and continental crust. She says young volcanic rocks are of interest because they’re a direct link to what’s going inside the Earth right now.

New magma now erupting from the Eyjafjallajokull volcano hardens to form new ocean floor. It means North America is moving about an inch and a half further from Europe each year and Iceland is being torn apart by the spreading action.

Seaman has been studying volcanoes and young volcanic rocks in Iceland since 2003, supervising the research projects of four graduate students. All such material on Iceland is extremely young, only 8 million years old compared to many hundreds of millions for other areas.

Iceland sits atop a big plume of mantle rock with a spreading, mushroom-shaped magma dome that is wider than all of Iceland. The current eruption is very interesting because it reportedly has a lot of gas content. In the past some such eruptions have contained fluorine which is dangerous to livestock and to people if it settles on crops, for example. It remains to be seen whether this one will prove to have this element in the ash.