If you're on a volcanic island - such as one of the Hawaiian Islands - you may find a particular type of rock, known as an ocean island basalt, or OIB. These rocks actually originated deep within the Earth, but volcanic eruptions brought them to the surface.
Although the rocks may look the same - and all of them originated from the same layer in the planet's interior - they're not all the same chemically, with differences in trace elements and isotopic composition. How these dissimilar rocks could come from the same place has long been a puzzle to scientists.
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Now, however, a group of present and former University of Arizona researchers have figured out why. They've created a model of dynamics in the Earth's mantle - the hot, semi-molten layer below the crust. It indicates that plumes of hot rock originate in the lower mantle and then physically interact with chemically distinct piles of material above them before they reach the surface. That, in turn, produces the variability in the chemistry of rocks that's seen in Hawaii.
Their findings are described in a recent article in the journal Nature Communications.
"This model provides a platform for understanding links between the physics and chemistry that formed our modern world as well as habitable planets elsewhere," Curtis Williams, the study's lead author, said in a release.
The differences in OIB samples provides scientists with new insights into the chemical structure and temporal evolution of Earth's interior.
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"In particular, it means that the Earth's mantle - the hot rock below Earth's crust but above the planet's iron core - is compositionally heterogeneous," said Williams, who now is doing post-doctoral work at the University of California, Davis. "Understanding when and where these heterogeneities are formed and how they are transported through the mantle directly relates to the initial composition of the Earth and how it has evolved to its current, habitable state."
Ocean island basalt from the Canary Islands comes from the same level deep within the planet.
Take a tour of some of the most impressive geological features around the world, as
kicks off worldwide. Above, a special landform at Zhangye Danxia Landform Geological Park, in northwest China's Gansu Province, formed from reddish sandstone that has been eroded over time into a series of mountains surrounded by curvaceous cliffs and many unusual rock formations. Danxia translates to "rosy cloud."
In Culebrita, part of the Culebra National Wildlife Refuge in Puerto Rico, visitors can relax in tidal pools that provide a jacuzzi-like bath -- and which capture small marine life at low tide.
Huge waves from the sea storm smash into the coast of Makurazaki, as Typhoon Vongfong barreled into Japan on Monday morning.
These cascades are one of dozens along the River Skoga in Iceland.
These natural sculptures in Ubon, Thailand, are made of sandstone that's thousands of years old. The “mushroom” shapes have been formed by wind and rain for centuries. They're called Sao Chaliang, which comes from the Thai word “sa liang” meaning stone pillar. Geologists believe that they're the remains of a dried up ocean that existed more than 1 million years ago.
Mayon Volcano in the Philippines is currently in seeing a "soft eruption," officials there said Sunday.
These naturally occurring limestone formations in Nambung National Park in Australia are called the Pinnacles. Rising above desert sand dunes, they were formed from the remains of seashells from an era when the area was full of marine life.