Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.

Science 25 August 1967:
Vol. 157. no. 3791, pp. 920 - 923
DOI: 10.1126/science.157.3791.920
Prev | Table of Contents | Next

Articles

Magnetic Anomalies over the Mid-Atlantic Ridge near 27°N

J. D. Phillips 1

1 Woods Hole Oceanographic Institution, Woods Hole, Massachusetts

Ten magnetic profiles across the mid-Atlantic ridge near 27°N show trends that are parallel to the ridge axis and symmetrical about the ridge axis. The configuration of magnetic bodies that could account for the pattern supports the Vine and Matthews hypothesis for the origin of magnetic anomalies over oceanic ridges. A polarity-reversal time scale inferred from models for sea-floor spreading in the Pacific-Antarctic ridge and radiometrically dated reversals of the geomagnetic field indicates a spreading rate of 1.25 centimeters per year during the last 6 million years and a rate of 1.65 centimeters per year between 6 and 10 million years ago. A similar analysis of more limited data over the mid-Atlantic ridge near 22°N also indicates a change in the spreading rate. Here a rate of 1.4 centimeters per year appears to have been in effect during the last 5 million years; between 5 and 9 million years ago, an increased rate of 1.7 centimeters per year is indicated. The time of occurrence and relative magnitude of these changes in the spreading rate, about 5 to 6 million years ago and 18 to 27 percent, respectively, accords with the spreading rate change implied for the Juan de Fuca ridge in the northeast Pacific.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Global Increase in Quaternary Explosive Volcanism.
J. P. Kennett, J. P. Kennett, and R. C. Thunell (1975)
Science 187, 497-502
   Abstract »    PDF »
Viscosity of the Atlantic Ocean Bottom.
C. H. Cramer and C. H. Cramer (1970)
Science 167, 1123-1124
   Abstract »    PDF »
Ocean Floor Spreading: Olduvai and Gilsa Events in the Matuyama Epoch.
D. A. Emilia, D. A. Emilia, and D. F. Heinrichs (1969)
Science 166, 1267-1269
   Abstract »    PDF »
Crustal Plates in the Central Atlantic: Evidence for at Least Two Poles of Rotation.
P. J. Fox, P. J. Fox, W. C. Pitman III, and F. Shephard (1969)
Science 165, 487-489
   Abstract »    PDF »
Potassium-Argon Ages and Spreading Rates on the Mid-Atlantic Ridge at 45{degrees} North.
F. Aumento, F. Aumento, R. K. Wanless, and R. D. Stevens (1968)
Science 161, 1338-1339
   Abstract »    PDF »
Continental Drift and Spreading of Ocean Floors.
E. Karp (1967)
Science 158, 947
   PDF »


To Advertise     Find Products

Science. ISSN 0036-8075 (print), 1095-9203 (online)