MOVE - Mid-Ocean Volcanoes and Earthquakes
A seismicity study of active magmatic and tectonic processes at ultraslow-spreading ridges
Ocean basins are formed by seafloor spreading at active mid-ocean ridges, the boundary between two divergent lithospheric plates. Mantle material is upwelling under the ridges and melts to produce magma which erupts onto the sea floor and crystallises at depth to produce new oceanic crust (Fig. 1). Crustal generation and plate separation rate keep pace over a wide range of spreading rates and produce oceanic crust with a uniform thickness of about 7 km. Models predict that at spreading rates below about 20 mm/y, the mantle looses heat by conduction and only small amounts of melt are produced at large depths. Consequently, magmatism and crustal thickness should decrease with decreasing spreading rate. Volcanic eruptions should be unlikely at ultraslow spreading ridges (<20 mm/y). Until recently, very little data from ultraslow-spreading ridges were available to verify this theory because these ridges are located in remote ocean basins, the ice covered Arctic Ocean and the rough ocean between Africa and Antarctica (Fig. 2).
Microearthquakes image the active tectonic and magmatic processes at mid-ocean ridges and therefore help to understand crustal generation. Due to their remote location, the microseismicity of ultraslow-spreading ridges is hardly explored.
My junior research group MOVE studies in various projects the seismicity of ultraslow-spreading ridges. As ocean bottom seismometers can not be used in ice covered oceans, we use drifting ice floes as platforms for our seismic stations. Apart from mid-ocean ridge earthquakes, we are also interested in the seismic signals produced by the ice itself.
Projects
- AMORE2001: Microseismicity pilot study at Gakkel Ridge
- AGAVE2007: Characterising microseismicity at Gakkel Ridge
- Submarine volcanism
- Singing icebergs
Support
Young Investigators Group: Emmy-Noether Programme, Deutsche Forschungsgemeinschaft (DFG)
Figures
Figure 1:
Simplified model of the generation of new oceanic crust at divergent plate boundaries. The mantle melts by decompression and rises to form magma which erupts onto the seafloor and crystallizes at depth to build a crust of about 7 km thickness independent of spreading rate. At ultraslow spreading rates, the melt production should cease and a thin peridotitic crust should form.
Figure 2:
The mid-ocean ridges worldwide are delineated by normal fault earthquakes (Harvard Catalog). Selected ridge systems are labelled together with their average full spreading rate in mm/y. The Gakkel ridge and the Southwestindian Ridge belong to the ultraslow-spreading ridges with spreading rates below 20 mm/y.
