Overview
About Katla
A volcano beneath an ice cap
The central volcano contains an ice-filled caldera measuring approximately nine by fourteen kilometres. A fissure swarm extends northeastward, making Katla a much larger volcanic system than its hidden summit alone. It belongs to Iceland's Eastern Volcanic Zone, where crustal extension provides pathways for magma. The ice covering the caldera is central to the region's volcanic hazards.
Explosive and effusive eruptions
Katla's characteristic eruptions produce basaltic tephra, the fragmented material expelled explosively from a volcano. Its record also includes silicic eruptions and large basaltic lava eruptions. The Eldgjá eruption around 939 CE is a major example of lava production along the associated fissure system. Katla therefore cannot be described through a single eruption style.
Jökulhlaups
When magma melts glacier ice, the resulting water can escape as a sudden flood called a jökulhlaup. Katla's 1918 eruption is a prominent historical example, connecting the volcano's eruptive history with flooding and sediment movement across the southern lowlands.
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