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At least 775 records · Page 43Linked to original sources
USGS2009

Earth's magnetic field complex: U.S. National activities during the Decade of Geopotential Field Research

The US geomagnetism community is supported by NASA, NOAA, USGS, NSF, DOD, and US universities. During the Decade of Geopotential Field Research, inaugurated in 1999 with the launch of the Danish satellite Ørsted on a US rocket, the US community has been involved in satellite mission development and analysis, instrument development, model development, and in the discovery and understanding of new processes with satellite magnetic signatures. The ESA Swarm mission has been a primary focus of the US community, with three US scientists on Swarm's Mission Advisory Group. Swarm will measure, for the first time, the E-W gradient of the magnetic field. One of us (T. Sabaka) is involved with the development of a Comprehensive inversion scheme as part of the SMART consortium. This effort is an outgrowth of the Comprehensive Model [1]. Swarm will also provide valuable observations for ionospheric specification and forecast. The geomagnetism group at NOAA (S. Maus, P. Alken and C. Manoj) has developed algorithms to estimate the strength of the eastward electric field (EEF). As the driver of the equatorial plasma fountain, the EEF is an important space weather parameter. ESA is considering the implementation of the EEF as a dedicated inversion chain in the Level-2 Facility. In 2006, NASA launched a minisatellite magnetometer constellation mission (ST-5) to test technologies and software. The ST-5 constellation featured the first along-track gradient measurements. NASA has also initiated efforts to study geomagnetism mission concepts after Swarm. One of the ideas under consideration is the systematic measurement of radial field gradients. Instrument development, and geomagnetic observatories, are also an integral part of the US effort. The past decade has seen significant advances in the development of a self-calibrating vector helium magnetometer, and in the automation of the US observatory network. Working in coordination with Intermagnet, the USGS Geomagnetism Program has made operational 1-second data acquisition at 13 of its magnetic observatories. The Program is also developing a realtime 1-minute and 1-hour Dst service. Within the past decade, US scientists have been leaders in the development of models that describe the global geomagnetic environment, including comprehensive models (the CM series), maps of the lithospheric field from satellite (MF-series), near surface maps of the lithospheric field (WDMAM-series), models of the thickness of the magnetic crust, the IGRF and World Magnetic Model series, ionospheric models such as the EEJM1, JVDM1, and the IRI, and data assimilation-based models (MoSST-series) that predict the future state of the geomagneic field.

Conference Paper↗
USGS1949

The relation between earth movements and volcanism in the San Juan Mountains of Colorado

The late Tertiary volcanism in the San Juan Mountains of southwestern Colorado followed a long interval during which the crust was stable. The volcanic rocks have been divided into four main groups, (1) those of pre‐Potosi (?) age in the eastern area, (2) the Lake Fork quartz latite, San Juan tuff, and Silverton volcanic series, (3) the Potosi volcanic series and the Fischer quartz latite, and (4) the Hinsdale formation separated by long intervals without eruptions. Each of the groups is made up of rocks from basalt to rhyolite with chemical and other peculiarities. During the eruption of a group there was little deformation but there was subsidence after the eruption of two of the groups and doming after the eruption of the last group. The magma moved into the area from the sides and was erupted about as rapidly as it moved.in. For the group named the Potosi volcanic series, the first eruptions had a composition near that of the primary magma ‐ dark quartz latites. Their eruption was followed by a short time without eruptions during which the magma became layered by crystal settling. The next eruptions were rhyolites followed abruptly, probably because of active movement of magna by dark quartz latites. The process was repeated three times. Subsidence caused by withdrawal of magma followed, and after a long time a new and different magma moved into the area and yielded the rocks of the Hinsdale formation. After the Hinsdale, a magma intruded the area with subsequent doming, but without eruptions.

Colorado↗