Petrology of Volcanic Products
Research
During and after the eruption in Surtsey, Icelandic and foreign scientists conducted diverse geological research on the island. The petrology of tephra and lava, the mineralogy of primary and secondary minerals, the chemical composition of gases in magma, and erosion by the sea and wind are examples of geological research projects that have been carried out. Examples of geophysical research projects are seismological measurements, aerial geomagnetic measurements, gravity surveys, and GPS measurements. The following is a discussion of the research data collected primarily after the end of the eruption.
Petrology of Volcanic Products
The magma and lava in Surtsey are of alkali olivine basalt, which is the type of basalt found in Vestmannaeyjar (Westman Islands) and on the Snæfellsnes peninsula. For the most part, the tephra is brown basalt glass that was formed by a quenching of the hot magma in the sea, but the lava is usually completely crystallized owing to a much slower cooling process. Large crystals of olivine and plagioclase can be found in the rock.
Chemical analysis of the rock at different times of the Surtsey eruption have shown that minor changes occurred gradually in the chemical composition of the magma as the eruption continued, more than is common in basalt eruptions. These changes most likely occurred over a long period in magma chambers several kilometers below the island. It has been argued that the original magma may have formed by partial melting of the rock in the earth’s upper mantle, at a depth of approximately 60-65 km.