Geology

Mediterranean Mud Pies

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Science  13 Jul 2001:
Vol. 293, Issue 5528, pp. 175
DOI: 10.1126/science.293.5528.175c

A mud volcano forms from the compression of fine-grained water-rich (usually clay) minerals, possibly mixed with hydrocarbon gases, producing a pressurized slurry that rises to the surface to create a bubbling mudflow. Over time, repeated eruptions can create a small edifice. These dome-shaped, meter-sized piles of mud can be found on the surfaces of accretionary prisms that develop at subduction zones.

On the seafloor of the eastern Mediterranean, a large number of mud volcanoes and mud pies—flat areas of mud outflows that resemble cow pies, only larger—have been mapped. These mudflows occur on the accretionary prism that is being formed by the subduction of the African plate beneath the Eurasian plate. Kopf et al. estimated the volume and porosity of the mud volcanoes, which are abundant close to the Eurasian plate, where compressive stresses are higher, and of the mud pies, which are abundant close to the African plate, where stresses are lower. The fluid flux from the mud pies was higher than that from the mud volcanoes and from estimates on other accretionary prisms. Thus previous estimates of fluid flux from a subduction zone may have been too low, and revisions of the estimated global fluid mass balance between crust and mantle related to subduction may be needed. — LR

Earth Planet. Sci. Lett.189, 295 (2001).

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