摘要:

New geodetic techniques and computer technology are providing scientists in the United States and other countries of North America with the precise tools needed to modernize the North American horizontal and vertical geodetic control networks—a web of geodetic survey monuments that spans the continent. When the project is completed in 1987, it will provide an improved base for mapping and engineering projects, crustal motion studies, inventories of natural resources, land parcel recordation, and the launch and recovery of space vehicles. In particular, the earth scientist will have available, in an instant, 100 years of historical geodetic data in computer‐readable form, supplying valuable information on crustal motion and earthquake prediction.The National Ocean Survey (NOS) through one of its main line components, the National Geodetic Survey (NGS), is responsible for the geodetic mission of the United States government. This task began on February 10, 1807, when the Congress enacted legislation proposed by President Jefferson to perform a ‘Survey of the Coast of the United States,’ thereby creating the first federal scientific agency. The first work performed was the measurement of two baselines and an 11‐station triangulation network in the vicinity of New York City during the period 1816–1818 [Powell, 1976], The first geodetic leveling survey was made during 1856 and 1857 by the U.S. Coast Survey (renamed the National Ocean Survey in 1970). This survey, directed by G. B. Vose, was in support of a detailed study of tides and currents in the vicinity of New York Bay and the Hudson River [B

ISSN:0002-8606    

DOI:10.1029/EO061i024p00489

年代:1980

数据来源: WILEY

摘要:

A relatively new dating technique that uses a radioisotope with an extremely long halt life has led some UCLA and Caltech researchers to picture the interior of the earth as of surprisingly simple structure. As they see it, the earth's mantle, which makes up about two thirds of the planet, is divided into two layers: an upper portion that supplies magma to the mid‐ocean ridges and other volcanic regions of the earth's surface and a lower layer that has remained untouched since the earth formed.In a Frontier session at the AGU Spring Meeting in Toronto, Don DePaolo of UCLA presented current findings from work with neodymium 143, the decay product of samarium 147. Frontier sessions highlight research of general interest in new areas of exploration. Research with neodymium has occurred only in the past 6 years, DePaolo said, because the measurement techniques available before then were not sensitive enoug

ISSN:0002-8606    

DOI:10.1029/EO061i024p00491-01

年代:1980

数据来源: WILEY

摘要:

The clearest picture yet of the electrical activity that evolved from a tornado‐producing thunderstorm shows that cloud‐to‐ground lightning hugged the leading edge of the storm center and became active only after the tornado died off.This data has been gained from a National Oceanic and Atmospheric Administration study of last spring's major tornado in Lawton, Oklahoma. The storm was one of 11 produced when an intense squall line formed in northern Texas and central Oklahoma. The severe storm activity on April 10, 1979, killed 54 persons in Lawton, and in Wichita Falls and Vernon,

ISSN:0002-8606    

DOI:10.1029/EO061i024p00492-01

年代:1980

数据来源: WILEY

摘要:

Despite the budget pinch, the National Aeronautic and Space Administration (NASA) has again awarded a cost‐plus‐management fee contract to Universities Space Research Associates of Columbia, Maryland, for the continued management and operation of the Lunar and Planetary Institute, Houston, Texas.Total cost and management fee for a 2‐year period through March 31, 1982, is $4,292,700. The work will be performed at the Institute, adjacent to the Johnson Space Center in Ho

ISSN:0002-8606    

DOI:10.1029/EO061i024p00493-01

年代:1980

数据来源: WILEY