Geology

A Map of Earth's Rocks

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Science  21 Dec 2012:
Vol. 338, Issue 6114, pp. 1512
DOI: 10.1126/science.338.6114.1512-c
CREDIT: J. HARTMANN AND N. MOOSDORF, GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS 13, 12 (7 DECEMBER 2012) © AMERICAN GEOPHYSICAL UNION

The distribution of rocks on Earth's continents reflects their geologic history spanning deposition, formation, deformation, metamorphism, uplift, and erosion. It also has important implications for engineering and resources, and the rocks exposed in areas of erosion influence global ocean chemistry and the composition of dust in the atmosphere. Hartmann and Moosdorf have compiled a global map of rock types exposed on Earth's continents using a variety of individual geologic maps and literature resources. Their high-resolution global map shows that most of the exposed rocks are sedimentary in origin, and most of these and about 20% of the total are carbonate rocks. Metamorphic rocks make up about 13%, as do igneous rocks, distributed roughly equally between volcanic and plutonic rocks. About 10% of Earth's continents are covered in ice or water. Rock types are distributed unequally over the continents; Africa is covered by extensive metamorphic rocks, whereas siliciclastic rocks (e.g. sandstones, shales, and conglomerates) dominate in North America and northern Eurasia.

Geochem. Geophys. Geosys. 13, Q12004 (2012).

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