Lava fountain and `a`a flow erupt from Pu`u `O`o vent, Kilauea Volcano

Photograph by J.D. Griggs
on 31 January 1984

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). Lava flows generated by effusive eruptions vary in shape, thickness, length, and width depending on the type of lava erupted, discharge, slope of the ground over which the lava travels, and duration of eruption.

For example, basalt lava may become `a`a or pahohoe, and flow in deep narrow channels or in thin wide sheets. Andesite lava typically forms thick stubby flows, and dacite lava often forms steep-sided mounds called lava domes.

Basalt lava erupts from Pu`u `O`o spatter and cinder cone at Kilauea Volcano, Hawai`i. Lava spilling from the cone has formed a series of `a`a lava channels and flows.

More about effusive eruptions

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