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Lithic breccia and ignimbrite erupted during the collapse of Crater Lake Caldera, Oregon Lithic breccia and ignimbrite erupted during the collapse of Crater Lake Caldera, Oregon

The climactic eruption of Mount Mazama (6845 y.B.P.) vented a total of ∼50 km3 of compositionally zoned rhyodacitic to basaltic magma from: (a) a single vent as a Plinian pumice fall deposit and the overlying Wineglass Welded Tuff, and (b) ring vents as ignimbrite and coignimbrite lithic breccia accompanying the collapse of Crater Lake caldera. New field and grain-size data for the ring...
Authors
T. H. Druitt, C. R. Bacon

A history of paleoflood hydrology in the United States A history of paleoflood hydrology in the United States

The origins of paleoflood hydrology in the United States can be traced back to the beginning of the 19th century, when windgaps and watergaps in the Applachians were believed to have been eroded by extraordinary floods as large lakes that were ponded behind the ridges rapidly drained. Sediment evidence for extraordinary floods was evoked several decades later when glacial sediments in...
Authors
John E. Costa

Implications of silicic vent patterns for the presence of large crustal magma chambers Implications of silicic vent patterns for the presence of large crustal magma chambers

On the basis of the distribution of silicic vents, many volcanic fields can be grouped with (1) igneous systems that may be small and whose vent locations are controlled by regional tectonics, (2) those that include sizable crustal magma bodies which erupt at sites determined by their anomalous local stress fields, or (3) relatively small volume systems that are transitional between...
Authors
Charles R. Bacon

A constitutive equation for mass-movement behavior A constitutive equation for mass-movement behavior

A phenomenological constitutive equation can serve as a basis for modeling and classifying mass-movement processes. The equation is derived using the principles of continuum mechanics and several simplifying assumptions about mass-movement behavior. These assumptions represent idealizations of field behavior, but they appear highly justifiable in light of the geomorphological insight...
Authors
Richard M. Iverson

Mid-Atlantic Ridge coccolith and silicoflagellate biostratigraphy, Deep Sea Drilling Project Sites 558 and 563. Mid-Atlantic Ridge coccolith and silicoflagellate biostratigraphy, Deep Sea Drilling Project Sites 558 and 563.

Low-latitude coccolith zonation can be used for biostratigraphy at Mid-Atlantic Ridge sites DSDP 558 (lat. 38°N) and DSDP 563 (lat. 34°N). The low-latitude zonal sequence from lower Oligocene to Holocene is interrupted by coolwater assemblages in upper middle Miocene and by hiatuses that removed the lower Pliocene and part of the upper Pliocene. A gap in the range of zonal guide fossil...
Authors
David Bukry

Tropical Pacific silicoflagellate zonation and paleotemperature trends of the late Cenozoic Tropical Pacific silicoflagellate zonation and paleotemperature trends of the late Cenozoic

Quantitative study of late Cenozoic silicoflagellates at tropical Pacific DSDP Sites 572 and 575 shows that the greatest amplitude of fluctuation in relative paleotemperature values occurred in the late Miocene. The coolest minimum paleotemperature values (near 75 = 30) also occurred in the late Miocene. The warmest intervals (Ts = 80 to 100) occurred in the middle Miocene and late...
Authors
David Bukry
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