History of Geophysical Research in The Netherlands ... - DWC - KNAW

of the Royal Netherlands Academy of Arts and Sciences to serve the ocean disciplines
in the fields of physical oceanography. meteorology. chemical oceanography.
marine biology. marine geology and geochemistry. and marine geophysics.
The Vening Meinesz Laboratory was charged with the marine geophysical program.
Funds became available for computer systems for on-board data handling.
satellite navigation systems. renovation of the gravimeter and the magnetometers.
and for a powerful compressor and airguns.
Apart from H. Nl.M. S. Tydeman the Marine Geophysics Group used chartered
cargo vessels. In 1975 research was carried out on the Mid-Atlantic Ridge by
means of the M.S. Aegeon Express. and in 1977. 1978 and 1979 with the M.S.
Tyro. again on the Mid-Atlantic Ridge and also in the basins east of the Ridge.
The first results of the geophysical measurements on board of the H.Nl.M.S.
Tydeman were embodied in a publication by Twigt. Collette and Slootweg (1979).
1.8.5. Atlantic Ocean: other subjects
J. A. Schouten developed in his thesis (1970) a fundamental method for analyzing
geomagnetic anomalies over ocean ridges. This method was applied to
the geomagnetic anomalies in the Atlantic Ocean and in the Bay of Biscay (Schouten
et al.. 1971). Rutten analyzed the anomalies off Iceland in his thesis (1975).
W. J. M. van der Linden (1975) presented an interpretation of magnetic anomaly
and basement trends in the Atlantic • concerning sea floor spreading in the Labrador
Sea. He also discussed morphology. magnetic and seismic characteristics
indicating that the area west of Iberia and Morocco is a deformed passive continental
margin (Van der Linden. 1979). He proposed (1980) that the eastern
Walvis Ridge is a continental fragment that was originally positioned marginal
to Africa.
It is the intention of the Marine Geophysics Group to study in thè near future.
among other subjects. sea floor spreading by investigating geomagnetic
anomalies and gravity on the Mid-Atlantic Ridge. This may result in more information
about movements of the continents on both sides of the Atlantic. In
1979 a study of the problem of young volcanism at the bottom of the Atlantic
Ocean was started. Measurements above the submarine Atlantic-Meteor mountains
were carried out.
I. 9. PALAEOMAGNETIC RESEARCH
Interest of Netherlands geologists and geophysicists in the magnetic properties
of rocks (and especially in palaeomagnetism. which is the fossil remanent
magnetization) was aroused around 1950. when a student of geology from
Utrecht University. J. Hospers • discovered Tertiary basalt flows in Iceland.
which showed a natural remanent magnetization whose direction was opposite
to the present direction of the earth '5 magnetic field. Hospers had collected
his basalt samples at the request of W. Nieuwenkamp (professor of petrology
at Utrecht) who assumed that the phenomenon of reversed magnetization of
basalt. which had been discovered by J. Brunhes in 1906 in France. perhaps
would appear also in basalts from Iceland. Since at that time a suitable apparatus
for measuring rock magnetism was not yet available in the Netherlands •
Hospers studied his rocks in the Geological Laboratory of Cambridge University.
where he finished his doctor's thesis. His investigation was published in
the Proceedings of the Royal Netherlands Academy of Arts and Sciences (Hospers.
1953 and 1954). Hospers concluded that the geomagnetic field must have
changed its polarity repeatedly during Tertiary times. that is to say that the
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