Nearly half of Iceland was formed from a slow spreading period from 9 to 20 million years ago (Ma).

[3] The buoyancy of the deep-seated mantle plume underneath has uplifted the Iceland basalt plateau to as high as 3,000 m (9,800 ft).

At Reykjavík towards the northern end of this peninsula the relative movement of the North American Plate away from the Eurasian Plate can be modelled as 1.883 cm/year (0.741 in/year), but less than 60% of this divergence is accommodated by tectonic structures just to the immediate east of Reykjavík, with most of the rest being absorbed by tectonic structures in the south-east of Iceland.

The most productive volcanic region is located under the Vatnajökull glacier in the mid-east of Iceland where all of about 1.853 cm/year (0.730 in/year) of extension is being accommodated near a plate triple junction.

[4] The historic subglacial volcanic eruptions result on the exposure, after the recent ice retreat, of distinctive flat topped landforms such as tuyas and rebound effects need to be accounted for in the seismic interpretations outlined below.

The southern boundary of the block is termed the South Iceland seismic zone (SISZ), where strike-slip earthquakes can occur.

[1]: 38, 41 There are two major and active transform faults zones striking west to north-west in northern and southern Iceland.

[9] The TFZ is defined seismologically as an approximate triangle with apex about 67°N, sides 120 km (75 mi) and base of 150 km (93 mi) off the north coast of Iceland, connecting the north Iceland volcanic zone (NVZ) and the southern end of the Kolbeinsey Ridge.

[1]: 50  Shear stress accumulated along the Húsavík-Flatey fault zone caused localized, tectonic rotation as evidenced by field and paleomagnetic observations.

[7] There is a significant change in the age and lithology of the volcanoes in a north-south direction near Reykjanes Peninsula due to bookshelf faulting.

[1]: 43 [7] In the transform fault zones of Iceland, earthquakes usually occur on small scales (micro-earthquakes) due to plate straining and pore fluid pressure.

[14][15] During these events, additional small scale earthquakes concentrated narrowly and linearly around the transform fault planes.

Not all the names used to classify the volcanoes into groups are yet standardised and not all the volcanic and tectonic relationships are well characterised due to issues such as accessibility or less current activity.

It is believed that the relative positions of the Icelandic hot spot and the active rift spreading axis have changed with time.

Each zone consists of 20–50 km (12–31 mi) wide belts and is characterised by active volcanoes, numerous normal faults, a high temperature geothermal field and fissure swarms.

[7] It accommodates the entire rifting of North Iceland and can be regarded at the present time to be in a steady state of spreading rate.

Seismic activity focuses in the Vatnajökull Glacier area which is the accepted location of the Icelandic hot spot.

[1]: 46  The EVZ started forming between 1.5 and 3 million years ago as a result of NVZ southward propagation.

[24] Long hyaloclastite ridges, formed by subglacial eruptions during the last glacial period, are distinctive structures in the EVZ.

[1]: 46  During the past glacial period, a huge volume of basaltic eruptions occurred, producing the long volcanic fissure swarms.

The WVZ remains active despite being an ultra-slow spreading center with extension rates of 0.3–0.7 cm/year (0.12–0.28 in/year) which is 20–30% of the total opening across south Iceland.

[1]: 44  It is located to the north of the plate triple junction manifest as the intersection of the WVZ, RVB and SISZ near the Hengill volcano.

[3] The extension component has been proposed to be caused by the opposite sense of rotation of crustal blocks to the north, which is in the Eurasian Plate and the Hreppar microplate to the south.

The SHRZ formed when the WVZ had the hotspot directly under it, and existed prior to the last historic rift zone jump.

[29] It is unknown if the SHRZ and or hot spot interactions are the reason for the SVB and this continues to be an area of study.

[30] It is now known that the magma production/maturation time scale at over 100,000 years, is an order of magnitude or more greater than that in other zones in Iceland favouring fractional crystallization mechanisms as primary.

[30] The SVB comprises the stratovolcanoes of Snæfellsjökull, Helgrindur (Lýsuskarð) and Ljósufjöll in a peninsular east to west lineament,[28] and is mainly basaltic volcanism from sources such as monogenetic cinder cones and isolated sub-glacial tuyas such as Vatnafell rather than from the long fissures found in the rift zones.

[29] Magma storage, in the studied regions of the belt, occurs just above the Moho, at about 22–11 km (13.7–6.8 mi) in the lower to mid crust,[25] which is not usually the situation in the rift zones where magma chambers occur in the mid to shallow crust at about 5 km (3.1 mi).

[3] Its three component central volcanoes of Öræfajökull, Esjufjöll, and Snæfell are in a south-west to north-east trending lineament and have rhyolite through to alkalic erupted basalts.

[33] There is some evidence from similarities in the compositional studies on Snæfell and the Upptyppingar subglacial volcano in the NVZ for the ÖVB being a flank zone.