AMORE2001

At ultraslow spreading rates, mantle melting and magma production are thought to be low and volcanic eruptions should be rare. However, in 1999, a large submarine eruption took place at eastern Gakkel ridge where full spreading rates are less than 10 mm/y. The eruption was accompanied by an unusually strong and long-lasting earthquake swarm. In summer 2001, the multidisciplinary Arctic Mid-Ocean Ridge Expedition (AMORE2001) studied the bathymetry, petrology, geophysical and oceanographic characteristics of Gakkel Ridge. They discovered robust magmatism at western Gakkel ridge, an amagmatic section further east and active volcanic centres at eastern Gakkel ridge (Fig. 1). New models are necessary to understand the processes generating oceanic crust at ultraslow spreading rates.

During AMORE2001, we made a first attempt at recording the microearthquake activity of the ridge using drifting ice floes as platforms for small seismological arrays. The unusual method worked: With the help of 4 three-component seismometers on one ice floe, we could distinguish between mostly horizontally travelling icequakes and vertically impinging earthquakes. We detected a wide variety of seismic signals of interest (Fig. 2) including local microearthquakes and the explosive sounds from an ongoing submarine eruption at the 85°E volcanic complex.

Dr. Vera Schlindwein