Fire and Ice: Living with Volcanoes, Earthquakes and Glaciers in Iceland
Abstract
Iceland is a volcanically-hyperactive part of the Mid-Atlantic Ridge, where the North American and Eurasian plates diverge above a mantle plume. As such, Iceland provides a natural laboratory for detailed studies of process occur along mid-ocean ridges (MORs) where two-thirds of Earth’s crust is formed. Similar to MOR spreading centers, volcanic activity and seismogenic faulting are focused along discrete rift zones connected by transform faults. The rift zones are marked by active central volcanoes, high-temperature geothermal activity, and dike/fissure swarms that have produced the largest historic lava flows on Earth. Historic eruptions have posed major threats for both the local population and north Atlantic airline transportation. The rift zones occur in an en echelon array along a 50 km wide plate boundary zone that propagates N and S away from the center of the Iceland hot spot. Rift propagation results in migration of the seismically active, EW transform fault zones. Block rotations caused by changes in finite spreading along the plate boundary zone are associated with widespread, NS, rift-parallel, strike-slip faulting that may reactivate older zones of weakness created during spreading. The widespread faulting in the plate boundary zones helps maintain transmissive pathways for domestic hot water wells over much of Iceland. Glacial melt waters are exploited for hydroelectric power, but subglacial volcanoes periodically cause catastrophic glacial outburst floods (“jökulaups”), building a broad outwash plain and threatening vulnerable infrastructure. The Icelandic population has learned to live with both the benefits and hazards of this very active geological environment.