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from article Colemanite
Fundamental building block in the crystal structure of colemanite.
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Image
from article Colemanite
Crystal structure of colemanite viewed down the a axis. The 〈Δ2□&x3009 x232A; rings link to form chains of borate polyhedra parallel to the c axis.
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from article Emerald
Emerald crystals. (Credit: Reimphoto/Getty Images)
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from article Pyroclastic rock
Pyroclastic rock. Bombs from Mauna Kea, Hawai'i, USA. (Credit: J. P. Lockwood/USGS Photo Library, Denver, CO)
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from article Pyroclastic rock
Distribution downwind of the pyroclastic fall deposit from the climactic eruption of Mount St. Helens, Washington, on May 18, 1980. The contours (isopachs) are drawn through points of measured equal thickness (in centimeters) of this ash layer.…
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from article Pyroclastic rock
Aerial view in March 1998 of the fan-shaped pyroclastic delta formed by repeated entries of pyroclastic flows and surges into the Caribbean Sea during the Soufrière Hills Volcano eruption in 1996–1997. (Credit: R.P. Hoblitt, USGS)
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from article Pyroclastic rock
Observed or postulated mechanisms for the generation of pyroclastic flow and surge deposits. (a, b) Mechanisms that commonly produce block-and-ash flow deposits. (b, c) Mechanisms that trigger laterally directed blasts. (d–f) Mechanisms that…
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from article Pyroclastic rock
Some variations in pyroclastic rock formations. (a) Layers of pyroclastic fall deposits from the eruption plume of the June 15, 1991, explosive eruption of Mount Pinatubo (Luzon, Philippines). This exposure, located about 9 km (5.5 mi) southeast of…
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from article Earth's interior
Speculative models of the interiors of the terrestrial planets. All are rocky, divided into a crust (not shown here), mantle, and metallic core. (After R. T. Merrill and M. W. McElhinny, The Earth's Magnetic Field, Academic Press, 1983)
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from article Earth's interior
Preliminary Reference Earth Model (PREM) for P- and S-wave velocities, vp and vs, and density ρ. In the part of the upper mantle where the model is anisotropic, velocities are given in both the vertical and horizontal direction. The broken lines…
