Felix Andries Vening Meinesz
Figure #1 - Felix Andies Vening Meinesz hard at work. (http://en.wikipedia.org/wiki/Felix_Andries_Vening_Meinesz)
Felix Andries (A.D.) Vening Meinesz was born on July 30, 1887 and was the youngest of four children of S.A. Venin Meinesz and C.A.C. den Tex. His father was the mayor of Rotterdam and then Amsterdam. Due to his family's background, one would have expected Vening Meinesz to have a career as a lawyer or magistrate. However, in high school he started studying science, technology, and commerce.
Vening Meinesz graduated from Delft Technical University in 1910 with a degree in civil engineering. His first job was with the Netherlands State Committee on Arc measurements where he was to measure gravity throughout the Netherlands, which would lead to Vening Meinesz' future career. After designing a two pendulum apparatus, he earned himself a doctors degree, cum laude in 1915.
Specific contributions to the theory of plate tectonics and/or our modern view of the solid Earth/Other important scientific contributions
Vening Meinesz designed a new gravimeter that consisted of two pendulums of the same size that hung in a frame but moved in opposite directions. Using mirrors and light beams the difference in the amplitudes of the pendulums were captured on film. Vening Meinesz soon realized that horizontal accelerations did not influence the amplitudes, which lead to more accurate measurements in gravitational forces . This apparatus originally was set up at 51 different monitoring stations around the Netherlands to measure the differences in gravity. The land measurements became such a success that he was encouraged to continue them at sea. For the apparatus to work at sea, Vening Meinesz needed to place the apparatus in a ‘swing' of sorts. (Figure #2 & #3)
Figure #2 - The new gravimeter created by Vening Meinesz. (Vening Meinesz, 1932)
Figure #3 - Gravimeter that was used on the submarine research missions. (Vening Meinesz, 1932)
This new gravimeter allowed for gravitational measurements at sea. Between 1923 and 1929 Vening Meinesz worked in small submarines to determine the shape of the Earth. While at sea he was interested in finding out if Earth's equator would deviate from a circle. From his observations, a deviation was never found. On the other hand, he confirmed that just like on the continents that Airy isostasy existed. This observation confirmed the existence of a thin low-density crust that floats on a high-density mantle. Knowing that continental topography would change the isostatic equilibrium, Vening Meinesz then focused his gravity measurements in the deep trenches of the oceans. This then lead to the discovery that strong negative isostatic anomalies ran parallel to the trenches. These negative anomalies would later become known as Meinesz belts.
These negative belts could only be explained by assuming that the elastic crust was held down in the trench by an external cause. A second positive belt was found on the seaward side of the trench could be caused by the upward flexing of the crust due to pushing down in the trench. This theory of flexure of the crust gave a thickness of 35 km. This thickness is still a valid figure for the mechanically strong parts of the oceanic lithosphere. Vening Meinesz did distinguish between chemical crust (subject to Airy isostasy) and ‘elastic' crust (defined rheologically). The flexure of the elastic crust helped him to expand the concept of isostasy. Whenever Airy isostasy deviated from the local density compensation at depth (trenches), Vening Meinesz introduced regional isostasy and compensation by taking a loaded crust into account.
This new idea became known as regional or Vening isostasy and is useful in connecting mountain building and loading of the oceanic lithosphere by volcanic edifices.
Examples of Isostasy (From http://userpage.fu-berlin.de/~hajo/Bratislava/Files/Isostat/Isostat.html):
Airy Isostasy - topographic heights are due to differences in crustal thicknesses.
Pratt Isostasy - topographic heights are due to changes in rock density.
Regional or Vening Isostasy - the lithosphere flexes under its own weight and shields the asthenosphere from the difference in pressures.
Other cool stuff you should know
One interesting fact about Vening Meinesz is that he was just over two meters or six and a half feet tall. So imagine a man of that stature in a small submarine for extended periods of time.
"Crustal Loading, Isostatic Models and Lithospheric Flexure." Web. 07 Feb. 2011. <http://userpage.fu-berlin.de/~hajo/Bratislava/Files/Isostat/Isostat.html>.
"Felix Andries Vening Meinesz." Wikipedia, the Free Encyclopedia. 19 Nov. 2010. Web. 31 Jan. 2011. <http://en.wikipedia.org/wiki/Felix_Andries_Vening_Meinesz>.
"Isostasy." Wikipedia, the Free Encyclopedia. 18 Jan. 2011. Web. 01 Feb. 2011. <http://en.wikipedia.org/wiki/Isostasy>.
"Vening Meinesz, Felix Andries." Complete Dictionary of Scientific Biography. 2008. Encyclopedia.com. 1 Feb. 2011 <http://www.encyclopedia.com>.
Vening Meinesz, F.A. Gravity Expeditions at Sea 1923-1930. Vol. I The Expeditions, the Computations and the Results. Rep. Delft: Nederlandse Commissie Voor Geodesie. Published 1932. Accessed 07 Feb. 2011. <http://www.ncg.knaw.nl/eng/publications/Green/03VeningMeinesz.html>.
Vlaar, N.J. "EGU Awards & Medals | Vening Meinesz." EGU Home. Web. 31 Jan. 2011. <http://www.egu.eu/awards-medals/awards-and-medals/award/portrait-vening-meinesz.html>.