tailieunhanh - Earth Sciences, History of

Asthenosphere A region of the earth’s upper mantle at a depth of approximately 75–150 km, characterized by low mechanical strength, attenuation of seismic shear waves, and partial melting. The term was coined in the 1910s by geologist Joseph Barrell to describe the zone in which isostatic adjustment occurs and basaltic magmas are generated. With the development of plate tectonics in the 1960s, the asthenosphere is now un- derstood as the plastic zone over which the rigid plates move | P1 GLM Final Pages Qu 00 00 00 00 EN004L-191 June 8 2001 19 25 Encyclopedia of Physical Science and Technology Earth Sciences History of Naomi Oreskes University of California San Diego I. Earth History and Geological Time II. Extinction Evolution and the Age of the Earth III. Continental Drift and Plate Tectonics IV. Oceanography Meteorology Seismology and Planetary Sciences V. Historiographic Reflections GLOSSARY Asthenosphere A region of the earth s upper mantle at a depth of approximately 75-150 km characterized by low mechanical strength attenuation of seismic shear waves and partial melting. The term was coined in the 1910s by geologist Joseph Barrell to describe the zone in which isostatic adjustment occurs and basaltic magmas are generated. With the development of plate tectonics in the 1960s the asthenosphere is now understood as the plastic zone over which the rigid plates move. Bathymetry Measurement of ocean depths. Benioff zones Zones of intermediate and deep-focus earthquakes dipping 30 -45 from the ocean toward the continents described by seismologist Hugo Benioff in the 1950s. While Benioff interpreted them as fault planes along continental margins these zones are now understood to mark the locations where oceanic crust is subducted beneath continental margins at convergent plate margins. Fennoscandian rebound In the early nineteenth century farmers and fishermen observed that the shorelines and coastal islands of Scandinavia were rising. In the early twentieth century this uplift was recognized as a regional phenomena encompassing Norway Sweden and Finland resulting from landscape adjustment to post glacial conditions. During the Pleistocene period the land had sunk under the weight of glacial ice. When the ice melted the land began to rebound in a gradual process still continuing today. Geognosy A term introduced in the eighteenth century by German mineralogist Abraham Gotlob Werner to denote factual knowledge of rocks minerals and their spatial .