A Surtseyan
eruption is a
volcanic eruption of
magma into shallow water (typically between 1 - 2
kilometres in depth).
This eruption causes explosive magma<->water interactions in an almost continuous series of blasts, producing an eruption column of up to 20 kilometres high in a characteristic rooster-tail shape. The debris produced by this explosion is a fine-grained pyroclastic material composed of glass shards, pumice and crystal fragments. This material can be deposited over a moderately sized area, as the particles are small enough to be carried for signficant distances on air currents.
This type of eruption was named after the first observed volcano of its type, Surtsey, which built up on the ocean floor south of Iceland in 1963.