Effusive eruption
An eruption dominated by the outpouring of lava onto the ground is often referred to as an effusive eruption (as opposed to the
violent fragmentation of magma by explosive eruptions).
Facts and Figures: The world's largest historical effusive eruption occurred in 1783 from the 25-kilometer-long Laki Fissure in
southern Iceland. The 8-month long eruption poured about 15 cubic kilometers of basaltic lava onto the ground and covered an
area of nearly 600 square kilometers. About 10'000 people, one-fifth of Iceland's population, and thousands of sheep, horses and
cattle died as a result of the eruption, primarily from starvation.
The largest known effusive eruptions on Earth have paved hundreds to thousands of square kilometers of its surface with basaltic
lava. Erupting hundreds of lava flows over a period of a few million years, scientists refer to the resulting deposits as flood
basalt and the areas covered as plateau basalt. One such area covered with flood basalt is the Columbia Plateau region of
eastern Washington and Oregon, USA. Between about 17 and 14 million years ago, a series of eruptions with a total volume more
than 175 million cubic kilometers covered an area of about 165'000 square kilometers. Even more voluminous plateau basalts are
located in South America, South Africa, and India.
 |
Eruptions of Kilauea volcano, Hawaii, are mainly effusive. Pahoehoe lava flow July 1991. Photo: J. Alean |