The Valley..#1More Tales from theValley..#2 Return to the Valley..#3 To Walk in the Valley..#4 To Catch a Smuggler..#5by BlueWords ThePower of the Valley..#6 To Catch a ChildKiller..#7 Stolen from the Valley..#8 To Catch a Friend..#9 byJay Alam To Catch aCold..#10 To Catch the Past..#11 To Catch aMonster..#12 To Catch Rhianna..#13The Compound..#14Watchers of theCompound..#15 All of the Valley stories in epub format Her NewWorldSection 1: LaunchingSection 2: TravelingSection 3: LandingSection 4: StartingSection 5: LearningSection 6: LivingSection 7: ChangingSection 8: SeeingSection 9: Surviving
Direct observations of submarine volcanic eruptions are very sparse. Radiometric age constraints on submarine lava flows are thus an essential component for understanding even the most recent histories of oceanic crust formation. Chronometers in the decadal to century time frame have heretofore been lacking. This study focuses on the development and application of 210Pb-226Ra disequilibria as a geochronometer to provide quantitative eruption age constraints over the past 100 years, using submersible-collected samples from the North Cleft segment of the Juan de Fuca Ridge (JDFR) and adjacent Axial seamount, 9 50'N East Pacific Rise (EPR) and Loihi (Hawaii), areas with known stratigraphic field relations between mapped lava flows. The data set provides a unique opportunity to calibrate the 210Pb-226Ra geochronometer because it represents a broad selection of "zero age" (210Po-210Pb dated) and near-zero-age submarine lavas (glasses). 238U-230Th-226Ra-210Pb radioactive disequilibria in these samples will be discussed to rationalize the range of conditions responsible for producing 210Pb-226Ra disequilibria (effective half life = 22 yrs) as an initial step towards using this signature to constrain eruption ages and petrogenetic time scales. We will also investigate the temporal aspects of petrogenetic conditions responsible for producing the other disequilibria in these rocks, without the uncertainty imposed by decay corrections for rocks of unknown age. These data augment those we previously reported from the Aldo-Kihi and neighboring lava flows at 17 26'S EPR (Rubin et al., EOS, 82, F1279, 2001). Systematic differences between and within study areas exist: most normal zero age MORB display modest 210Pb deficits (3-10%); older MORB (the N-cleft sheet flow) have smaller deficits (0-3%); rocks erupted in 1998 from Axial seamount have 8-15% 210Pb excesses; and, rocks erupted in 1996 at Loihi are in equilibrium within error. Disequilibria amongst other nuclides are all
Nikki Glass 3 Epub Format
2ff7e9595c
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