Case Study: Volcanic Eruption — Eyjafjallajökull, Iceland, 2010

Between 20 March and late June 2010, the Eyjafjallajökull (pronounced roughly "AY-ya-fyat-la-yoh-kutl") volcano in southern Iceland erupted, producing lava flows, jökulhlaups and — most consequentially — an ash plume that caused the largest disruption to European airspace since the Second World War. This case study demonstrates that volcanic hazards can have impacts at scales far beyond the local eruption site. It addresses Edexcel A-Level Geography Enquiry Question 2 (EQ2): Why do some tectonic hazards develop into disasters?

Tectonic Context

Iceland occupies a unique tectonic position — it sits on both the Mid-Atlantic Ridge (a divergent plate boundary) and a mantle plume (hotspot). This dual tectonic setting produces exceptionally high rates of volcanic activity.

Tectonic Detail	Information
Plate boundary	Divergent — North American and Eurasian plates moving apart at ~2.5 cm/year
Hotspot	Iceland hotspot (mantle plume) beneath the Mid-Atlantic Ridge
Volcano type	Stratovolcano (composite), partially covered by Eyjafjallajökull ice cap (~200 m thick)
Summit elevation	1,651 m
Ice cap area	~100 km²
Previous eruptions	920 CE, 1612 CE, 1821–1823 (14-month eruption)
Magma type	Initial: basaltic; later: intermediate (trachyandesitic)

Eyjafjallajökull is closely linked to the much larger and more dangerous Katla volcano, located 25 km to the east. Historically, eruptions of Eyjafjallajökull have been followed by eruptions of Katla (this pattern held in 920 and 1612, though Katla did not erupt after the 2010 Eyjafjallajökull event).

The Eruption: Phases and Processes

The eruption occurred in two distinct phases:

Phase 1: Fimmvörðuháls Flank Eruption (20 March – 12 April 2010)

Aspect	Detail
Location	Fimmvörðuháls pass, between Eyjafjallajökull and Mýrdalsjökull ice caps (not beneath the glacier)
Eruption style	Effusive — basaltic lava flows and fire fountains
Lava composition	Basaltic (low silica, low viscosity)
Hazards	Localised lava flows; no significant ash; hiking trails closed
Impact	Minimal — attracted tourists ("volcano tourism")

Phase 2: Summit Eruption (14 April – late June 2010)

Aspect	Detail
Location	Summit caldera, beneath the Eyjafjallajökull ice cap
Eruption style	Explosive — phreatomagmatic (magma-ice interaction)
Lava composition	Trachyandesitic (intermediate silica, higher viscosity)
VEI	4 (Cataclysmic)
Ash plume height	Up to 9–11 km (reaching the tropopause and lower stratosphere)
Ash production	~250 million m³ of tephra
Duration	~6 weeks of significant eruption; intermittent activity until late June

The transition from Phase 1 to Phase 2 was critical. When the eruption migrated to the summit caldera beneath the ice cap, meltwater flooded into the vent, causing phreatomagmatic explosions — violent interactions between magma and water that fragment the magma into extremely fine-grained ash particles (< 0.1 mm). This fine ash remained suspended in the atmosphere for extended periods, creating the aviation hazard.

graph TD
    A["Magma rises to summit"] --> B["Encounters 200m thick ice cap"]
    B --> C["Rapid ice melting"]
    C --> D["Meltwater enters vent"]
    D --> E["Phreatomagmatic explosions"]
    E --> F["Fine-grained ash plume<br/>rises to 9–11 km"]
    E --> G["Jökulhlaups<br/>(glacial outburst floods)"]
    F --> H["SE winds carry ash<br/>over Europe"]
    G --> I["Flooding of Markarfljót river<br/>800+ evacuated"]

Exam Tip: The reason the Eyjafjallajökull eruption was so disruptive was not its magnitude (VEI 4 is moderate) but the combination of factors: (1) intermediate magma composition producing fine ash; (2) ice-magma interaction creating phreatomagmatic fragmentation; (3) wind direction carrying ash southeast directly over Europe's busiest airspace; and (4) the eruption's multi-week duration. Always emphasise this combination in exam answers.

Local Impacts

Jökulhlaups (Glacial Outburst Floods)

The melting of the ice cap produced jökulhlaups that flooded the Markarfljót river system:

Flood Detail	Information
Peak discharge	~3,000 m³/s (compared to normal flow of ~50 m³/s)
Evacuations	~800 people evacuated from farms in the Markarfljót floodplain
Damage	Roads and bridges damaged; farmland flooded; no deaths
Response	Civil Protection Agency ordered pre-emptive evacuation based on monitoring data; all evacuees returned within days

The successful evacuation was attributed to Iceland's extensive monitoring network and well-rehearsed emergency procedures. The Icelandic Meteorological Office (IMO) had been monitoring increased seismicity and GPS-measured ground deformation since early 2010, providing advance warning.

Agricultural Impact

Impact	Detail
Ash fall	Up to 20 cm of ash fell on farms within 20 km of the volcano
Livestock	Animals exposed to fluorine-contaminated ash; animals brought indoors; supplementary feeding required
Water contamination	Surface water contaminated by ash; groundwater unaffected
Pasture	Contaminated; livestock could not graze for several weeks
Crop damage	Limited (eruption occurred before main growing season)
Long-term	Ash improved soil fertility once incorporated; pasture recovered within one growing season

Case Study: Volcanic Eruption