Atomic clock acts as volcanic early warning system

Monitoring 9,192,631,770 cycles of the electromagnetic radiation emitted or absorbed by the ground state hyperfine transition of the caesium atom (the Si definition of a second), atomic clocks measure time with exceptional accuracy. The best atomic clocks are so precise that they would lose less than a second over a 10bn year period.

The scientists' analysis shows that the slow down of time predicted by Einstein's theory of general relativity can be measured by local clocks and used to monitor volcanoes. General relativity states that clocks positioned at different distances from a massive body like the Earth have different tick rates. The closer a clock is to a massive object, the slower it ticks because of the increased gravity. Similarly, large subterranean objects influence the tick rate of local clocks on the Earth’s surface. New lava filling a magma chamber beneath a volcano makes a clock located above that volcano tick more slowly than a clock that is located further away.

Currently, volcanoes are monitored using GPS receivers but the resulting data often needs to be integrated over several years before an estimate of the volume of new magma can be made. A network of local, highly precise atomic clocks could provide the same information within a few hours, making it possible to monitor processes inside volcanoes more closely and to make better predictions for future volcanic eruptions.

The international team has also revealed that a ground-based network of atomic clocks could monitor the reaction of the Earth’s crust to solid Earth tides. The Earth moves in the gravitational field of the Sun and the Moon and when it reacts to these external fields by deforming (which in turn leads to ocean tides and to the ground on the continents lifting and falling regularly), the ground can rise as much as 50cm. A global network of atomic clocks connected via fibre optic cables, could provide continuous measurements of the Earth tides and check existing theoretical models. It would also be possible to examine any local differences in the response of the Earth’s crust to the Earth tides.

Dr. Ruxandra Bondarescu commented: “We need this additional tool to monitor magma movement under volcanoes such as the Yellowstone supervolcano, which is overdue for an explosion that would alter life on Earth as we known it."