Emplacement of Basaltic Lava Flows
The focus of this research is to understand the style of emplacement and morphogenesis of historic basaltic pahoehoe lava flows, using field sites in Iceland. To date, investigations of two lava flow fields have been undertaken: the Skaftareldahraun (or Laki flow field) and Hallmundarhraun. The research has involved high resolution mapping of flow surface landforms with GPS, supported by near-surface geophysical methods of remotely mapping subterranean features. On the 1783/4 Laki flow field, a study of the upper eastern arm, known locally as the Eldhraun, revealed a complex assemblage of landforms, including over 11km of accessible lava tube cave passage, closed depressions, lava rises, lava rise pits, collapse pits, squeeze outs and collapse trenches. By accurately mapping the position and morphology of these features, it was possible to work out their genetic relationships, which in turn enabled an interpretation of the emplacement history of this part of the flow field. Work on the Hallmundarhraun has involved more geophysical investigation than on the Eldhraun. A particularly intriguing feature on this 50km long, tenth century, lava flow is the long sinuous chain of crater-like features, known as shatter rings, each ring positioned at the summit of a small lava shield.
Invesigation with magnetometry and ground penetrating radar revealed that the craters overlie the route of what was probably the lava flow's master lava tube system, drained and accessible parts of which may be observed in the well-known Surtshellir/Stefánshellir and VĂdgemir lava tube caves. On-going research on the Hallmundarhraun is revealing an emplacement history that is far more complex than originally envisaged, probably involving repeated injection of fluid lava through the master lava tube system during separate phases of effusive activity at the vents. Of additional interest, the research on the Hallmundarhraun represents the first ever successful attempt to locate and map voids in lava flows from the surface, and the geophysical methods developed on the Hallmundarhraun are now recognised to be of use in civil engineering contexts. This approach to researching the emplacement history of cooled lava flows is providing substantial new information and possible future sites for investigation are planned in Iceland, Mt Etna and Lanzarote.
For more details contact Dr Chris Wood
