A volcanologist stands inside a fracture in Iceland’s northern volcanic zone
Volcanism on Earth is dominated by eruptions beneath the sea, at mid-ocean ridges that extend over 40 thousand miles. As Vine and Matthews elegantly demonstrated using magnetic stripes on the sea floor, it is here that rising magma creates new oceanic crust where two tectonic plates diverge. Shifts in the magnetic pole from north to south provided a pendulum against which the timing of volcanism could be calibrated.
However these deeply-submerged underwater eruptions seldom make the news, as the rising magma is quenched by seawater, gently forming pillows of lava. However, in the north Atlantic mid-ocean ridge volcanism is boosted by a plume of upwelling material from deep in the mantle. This creates a unique situation where the mid-ocean ridge rises above the sea, to form an island whose volcanoes are definitely newsworthy – Iceland.
Like the sea floor, the geological map of Iceland also shows stripes, with the youngest material in the centre. These stripes record another fundamental change to the Earth’s surface. Eruptions during glacial periods have created mountains of volcanic glass moulded within thick ice sheets, towering above flat-lying lavas erupted during interglacial periods. Scientists have recently proposed that changing ice thicknesses may influence volcanism, with unloading due to melting of ice making volcanoes more active.
One of my research goals is to better understand the behaviour of Iceland’s hazardous ice-covered volcanoes, as magma and glacial meltwater are an explosive cocktail that can trigger far-reaching ash plumes and colossal floods. Forecasting of future events at Eyjafjallajokull or Katla requires knowledge of how magma moves within volcanic systems, and clues are frozen into lava and ash formed in past eruptions.
A key future research question is whether climatic warming in the 21st century will lead to larger or more frequent eruptions at the many ice-covered volcanoes from Iceland to the Andes. Glaciers on many volcanoes are rapidly thinning, but it is unclear how much unloading of ice is needed for volcanoes to become more active.
Dr Hugh Tuffen is a University Research Fellow at Lancaster Environment Centre, Lancaster University. His work is on fracture and fluid flow in volcanic conduits and lava domes.