Sunday, April 26, 2015
A volcano eruption in the Canary Islands of the Atlantic has helped prove those islands have a lot in common with the Hawaiian Islands—geologically.
(Image: The Canary Islands from space. Credit: European Space Agency.)
The October 2011 eruption off the Canary island El Hierro trapped ancient rock from the seafloor inside fresh volcanic pumice, and drove it to the surface.
In some of that rock, scientists found tiny fossils that date to the Cretaceous period.
The Cretaceous was 65 to 145 million years ago, when dinosaurs roamed the planet, flowering plants were spreading, ants and butterflies appeared, and humans were still a gleam in Mother Nature’s eye.
The floating rocks from the El Hierro eruption contained “sedimentary xenoliths.” A xenolith is an older rock that gets trapped inside lava.
Inside some of that older rock, the scientists found tiny fossils that they were able to date, and researchers led by Kirsten Zaczekconcluded that by dating the rock, they were able to conclude that the Canaries were formed through the same process by which the Hawaiian Islands were formed.
“The sedimentary xenoliths were contained in ‘floating stones’ of up to soccer ball size that consisted of dominantly light-coloured pumiceous glass coated with basanite, which we have termed ‘xeno-pumice,’” the scientists wrote.
Their discovery led to the overturning of the dominant theory about the formation of the Canary islands and shed information that clarified ancient geologic mysteries.
“The origin and life cycle of ocean islands have been debated since the early days of geology,” they wrote.
A popular account in phys.org is here.
Another from Science Daily is here.
Zaczek and her colleagues were able to show that the Canary Islands were successively older going from east to west. It suggested that, like Hawai`i, that the Canaries were formed from a volcanic plume that erupts through the earth’s mantle as the region's tectonic plate moves over the plume.
“The erupted El Hierro sedimentary relicts provide crucial support for an east-west age progression for the onset of volcanism in the Canary archipelago by demonstrating unequivocally that the youngest pre-island sediment is located beneath El Hierro.
“The fossil evidence from El Hierro therefore concludes the current debate on the origin of the Canary Islands and reinstates a mantle-plume as the most plausible cause of volcanism in the Canary Islands,” the paper’s authors conclude.
They found in the pumice-encased sediment rock a lot of coccolithophores.
These are open ocean single-celled algae that deposit calcium, and which becomes fossils after settle to the sea floor. Different species of coccolithophores have gone extinct at known times, making them good markers for dating geological sediment.
The Hawaiian Islands are also older as you move west from the newest, Hawai`i Island.
© Jan TenBruggencate 2015