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Space surveillance shows that the ground beneath our feet is not quite as solid as it seems. Earth’s crust is continuously in motion, driven by gradual geological shifting that occasionally speeds up, in the potentially destructive form of earthquakes or volcanoes.

Looking down on Earth from hundreds of kilometres away in space has proven a surprisingly accurate way of detecting slight sub-centimetre-scale motion across tens of kilometres of terrain that might otherwise go unobserved.

Combining together multiple radar images of the same location through a technique called Synthetic Aperture Radar Interferometry highlights tiny land changes that have occurred between acquisitions. It’s a technique that has been used to survey the seismically active belts that make up around 15% of global land area, in order to search out previously unknown fault lines.

InSAR has also been used to survey supposedly extinct volcanoes – slight signs of ‘breathing’ indicate continued active status.

ESA’s GOCE mission peers deeper into solid Earth by measuring slight variations in Earth’s gravity field to detect hidden features, such as subsurface water aquifers, deep ocean currents, volcanic magma plumes and polar ice sheets.

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CryoSat unveils secrets of the deep

03 October 2014

ESA's ice mission has been used to create a new gravity map, exposing thousands of previously unchartered 'seamounts', ridges and deep ocean structures. This vivid new picture of the least-explored part of the ocean offers fresh clues about how continents form and breakup.

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GOCE reveals gravity dip from ice loss

26 September 2014

Although not designed to map changes in Earth's gravity over time, ESA's extraordinary satellite has shown that the ice lost from West Antarctica over the last few years has left its signature.

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Geoid

The use of satellite data in the detailed study and precise measurement of the Earth's geoid in order to improve our understanding both of the Earth's interior, and dynamic topography of the world's oceans.

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Geomagnetism

Observations show that geomagnetic field lines follow closely the atmospheric circulation patterns and that geomagnetic field variations are precursors to climate change. Therefore close monitoring of the local and global geomagnetic field variations by satellite systems will assist prediction of hurricane tracks, intensification and also long-term weather trends.

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Tectonics

The monitoring of the movement and deformation of the Earth's crust with the aim of understanding its evolution and of predicting major seismic events. Interferometry is an important technique in this application.