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Deep magmatic plumbing of mid-ocean ridges revealed
August 25, 2005New images suggest that the Earth's lower oceanic crust is generated from multiple magma sources
Some of the highest quality images ever taken of the Earth's lower crust reveal that the upper and lower crust form in two distinctly different ways. A team led by researchers from Columbia University's Lamont-Doherty Earth Observatory will publish the results of their work in the August 25 issue of the journal Nature.
The Earth's oceanic crust is formed from magma bodies located beneath mid-ocean ridges. Although axial magma chambers, magma bodies located in the mid-crust, are known to be responsible for generating the upper oceanic crust, it has so far been unclear if the lower crust is formed from the same source or if it primarily arises from deeper "magma lenses" - smaller bodies located at or near the base of the crust.
Researchers from Lamont-Doherty as well as the Scripps Institution of Oceanography and the Woods Hole Oceanographic Institution collected seismic data of the oceanic crust beneath the seafloor off the coast of Washington, Oregon and northern California. To form the images, they analyzed sound waves that bounced off of structures deep in the Earth, a process similar to that of creating an ultrasound image. The resulting images are the first of their kind showing solidified lenses and sills, narrow lateral intrusions of magma, embedded within the crust/mantle boundary known as the Moho transition zone. The presence of such bodies that deep near a mid-ocean ridge suggests that the lower crust is at least partially formed from several smaller sources of magma rather than from a single large source located in the middle of the crust.
"This demonstrates quite strongly that the process of crustal formation is more complex than generally believed," said Mladen Nedimovic, lead author on the study and a Doherty Associate Research Scientist at Lamont-Doherty. "It also favors the emerging view that volcanoes have a complicated plumbing system consisting of many interconnected sills and magma conduits. We obviously still have a lot to learn about what goes on beneath the surface of the Earth."
The Earth Institute at Columbia University
Researchers from Lamont-Doherty as well as the Scripps Institution of Oceanography and the Woods Hole Oceanographic Institution collected seismic data of the oceanic crust beneath the seafloor off the coast of Washington, Oregon and northern California. To form the images, they analyzed sound waves that bounced off of structures deep in the Earth, a process similar to that of creating an ultrasound image. The resulting images are the first of their kind showing solidified lenses and sills, narrow lateral intrusions of magma, embedded within the crust/mantle boundary known as the Moho transition zone. The presence of such bodies that deep near a mid-ocean ridge suggests that the lower crust is at least partially formed from several smaller sources of magma rather than from a single large source located in the middle of the crust.
"This demonstrates quite strongly that the process of crustal formation is more complex than generally believed," said Mladen Nedimovic, lead author on the study and a Doherty Associate Research Scientist at Lamont-Doherty. "It also favors the emerging view that volcanoes have a complicated plumbing system consisting of many interconnected sills and magma conduits. We obviously still have a lot to learn about what goes on beneath the surface of the Earth."
The Earth Institute at Columbia University
Investigating the deepest layers of the Earth's crust
The deep layers of the Earth's crust and the upper part of its mantle have been the target for investigation by a number of research groups at the EHU/UPV. This deep zone, and the processes that have taken place there in the past, can be investigated by means of studying those rocks which today are lying on the surface but which in past geological periods were at great depths. On the Iberian Peninsula there are few places where one can find rocks which have been submerged at such depths (greater than 50-60 km). One of these is situated in the north-east zone of the Iberian Massif, occupying parts of Galicia and north-east Portugal. Geologically the area is known by the name of the North Eas
New activity on old fault lines: French earthquake no surprise
The relatively powerful earthquake that hit eastern France last Saturday confirms the findings of the postgraduate research currently being conducted by Gideon Lopes Cardozo at the Université Louis Pasteur in Strasbourg and the Faculty of Earth and Life Sciences at the VU Amsterdam. Lopes Cardozo is investigating the causes of earthquakes in the southern part of the Rhine Graben. His research is sponsored by the European Union and has shown that the movements in the earth's crust in the area around the Rhine occur along fault lines that have a long geological history. Until recently, it was thought that these movements actually took place more often on younger fault lines. The earthqu
Discovered: Cooling system under the sea floor
EMBARGO: February 5th, 8 pm The scientific, technical and logistic support of the geo scientists from Bremen, Prof. V. Spiess, Dr. L. Zühlsdorff and Prof. H. Villinger was instrumental in the discovery of a 50 km long cooling system by US-scientists under the sea floor off the north-west American coast. Its cornerstones are rocky outcrops which reach up to hundreds of meters from the ocean floor. They transfer heat from the earths crust to the waters above. The new studies concerning the heat balance of our planet will be published in the February 6th edition of the scientific journal "Nature". The international team of scientists studied the eastern flank of the Juan de Fuca R
GPS technology aids earthquake research
Scientists' understanding of the movement of the Earth's crust is being helped by new observing facility which is taking measurements that may one day help predict earthquakes. Newcastle University's School of Civil Engineering and Geosciences has become only one of two UK centres feeding Global Positioning System (GPS) data into the International GPS Service (IGS), which researchers and professionals throughout the world - including geophysicists - can access via the Internet. The other centre is the Royal Greenwich Observatory in Herstmonceux, East Sussex. The data is collected via a GPS station 20 miles north of the city, at the University's farm, Cockle Park, in Morpeth, Northumberland,
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