Dynamics of Volcanic Systems in Iceland: Example of Tectonism and Volcanism at Juxtaposed Hot Spot and Mid-Ocean Ridge Systems

Abstract

Volcanic systems are swarms of tectonic fractures and basalt volcanoes formed as a result of plate-pull (as the plates are pulled apart) associated with the mid-ocean ridges and the magma dynamics of the Iceland Mantle Plume. Most systems are 40–150 km long, 5–20 km wide, and develop a central volcano. They supply magma to all eruptions in Iceland. Data obtained in the last few years have greatly improved our knowledge of their volcanotectonic environment; as a result, the geometry of the plume is better constrained, and the crust, previously considered thin (∼10 km), is now modeled as thick (∼20–40 km). Depending on the location of the volcanic systems, their activity either decreases or increases faulting in the two main seismic zones. From this, we can infer that emplacement of the feeder-dike to the largest historical eruption in Iceland (that of Laki in 1783) increased shear stress in the South Iceland Seismic Zone and almost certainly triggered the largest (M∼7.1 in 1784) historical earthquake in Iceland. [ Addendum posted 20 April, 2010 ]

Volcanism in Iceland in historical time: Volcano types, eruption styles and eruptive history

“…Later studies, independently, reached the same conclusions regarding the overall volcanotectonic architecture in Iceland (e.g. Walker, 1959Walker, , 1963Walker, , 1964Walker, , 1975Saemundsson, 1974Saemundsson, , 1978Saemundsson, , 1979Tryggvason, 1973;Jakobsson et al, 1978;Jakobsson, 1979a) and as such established the volcanic system as a fundamental structure in the volcanic successions (Jakobsson, 1979b;Gudmundsson, 1995bGudmundsson, , 2000.…”

“…Gudmundsson, 2000). Collectively, the regions of active volcanism cover ∼30,000 km 3 or about one third of Iceland.…”

“…Modified after Saunders et al (1997). Gudmundsson, 2000). Of those the most prominent belt is the axial volcanic zone, the loci of active spreading and plate growth that follows the plate boundary across Iceland from Reykjanes in the southwest toÖxarfjörður in the north (Fig.…”

“…(b) Another where rifting episodes on volcanic systems are driven by the magma pressurization in large and elongate reservoirs at the base of the crust (>20 km depth) and subsequent injection of subvertical dykes into the upper crust (e.g. Gudmundsson, 1987aGudmundsson, , 1995bGudmundsson, , 2000.…”

“…The recurring eruptions occur on circular summit vents or ring fractures within the summit caldera or on short, often radial, fissures on the outer flanks of the volcano (e.g. Gudmundsson, 2000). Published studies of Tertiary-age central volcanoes show that their construction was dominated by effusion of basaltic lavas, with small but significant contribution from eruptions of intermediate and silicic magma (e.g.…”