Earth on the move In 2011, the violence of the Tohoku-oki earthquake in Japan was a reminder that the Earth’s surface is constantly changing. By scrutinizing earthquakes and volcanic eruptions, researchers are constantly improving their predictions of such natural disasters. Dormant volcanoes are lighter sleepers 45° 45° than predicted 40° 40° In terms of volcanic eruptions, it was thought until now that, once a volcano’s magma chamber had cooled down, it remained dormant 35° 35° for centuries before it could be remobilized by fresh magma from deep inside the Earth. However, a theoretical model developed by two geophysicists has shown that reawakening can take place in 30° 30° just a few months. The reliability of this new model, which has been verified for two major eruptions, should lead to a reassessment of the dangerousness of some dormant volcanoes. TECU 135° 140° 145° 150° 125° cm 130° 135° 140° 145° 150°130°125°25°25° Nature March 2011 -0,6 -0,4 -0,2 0 0,2 0,4 0,6 950 25 15 10 5 0 -5 -10 -15 -25 -600 Left, disturbances in the ionosphere observed over Japan 25 minutes after the Tohoku-oki earthquake. Right, model of the tsunami generated by the earthquake. Space surveillance of tsunamis takes shape Tsunami warning sign in Constitución, in the Maule region of Chile. The strong mobilization of the French scientific community after the Tohoku-oki earthquake in Japan on March 11, 2011 contributed to the first, highly-accurate study of the disturbances caused by a powerful earthquake in the upper atmosphere. By using GPS sensors and observing the change in the airglow caused by certain seismic waves, the researchers were able to model the motion of a real atmospheric tsunami that traveled from Japan to Hawaii. This is a first step towards a novel method for the monitoring of tsunamis, based on the disturbances they cause in the ionosphere. Geophysical Research Letters July 2011 42 A year at CNRS 2011
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