In this paper we present a time-stratigraphic scheme and geologic time scale for the protoplanet Vesta, based on global geologic mapping and other analyses of NASA Dawn spacecraft data, complemented by insights gained from laboratory studies of howardite–eucrite–diogenite (HED) meteorites and geophysical modeling. On the basis of prominent impact structures and their associated deposits, we pro...

First posted April 6, 2023 For additional information, contact: Director, Geologic Hazards Science CenterU.S. Geological Survey1711 Illinois StreetGolden, Colorado 80401Contact Pubs Warehouse Debris flows are a type of mass movement that is more likely after wildfires, and while existing hazard assessments evaluate the rainfall intensities to trigger debris flows, no operational assessment exis...

Geologic process, including tectonics and global climate change, profoundly impact the evolution of life because they have the propensity to facilitate episodes of biogeographic differentiation and influence patterns of speciation. We investigate causal links between a dramatic faunal turnover and two dominant geologic processes operating within Laurentia during the Late Ordovician: the Taconia...

Amazonian The youngest of the geologic epochs on Mars identified through geoiogic mapping of superposition relations, and the area! density of impact craters. caldera An irregular collapse feature formed over the evacuated magma chamber within a volcano. central volcano Emplacement of volcanic materials from a centralized source vent rather than along a distributed line of vents, composite volc...

As part of a 3.year program of geologic mapping from the Yukon border south through the Midway, Cassiar and Erickson mining camps (Nelson and Bradford, 1987a; 1987b; 1989, this volume; Nelson et al. 1988a; 1988b), I:25 000.scale mapping was conducted in the northeast quarter of the Needlepoint Mountain (104P/4) map area during the 1988 field season (Figure l-35-1). Since Gabrielse’s ( 1963) ori...

PRD1, an icosahedra-shaped, 62 nm (diameter), double-stranded DNA bacteriophage with an internal membrane, has emerged as an important model virus for studying the manner in which microorganisms are transported through a variety of groundwater environments. The popularity of this phage for use in transport studies involving geologic media is due, in part, to its relative stability over a range ...