Effusion (Latin effusio, outpouring ) or effusive volcanic activity in the volcanism is next to the ejection of one of the two main types of volcanic eruptions.
The effusion is in contrast to the explosive volcanic activity ejective the more or less quiet outflow of lava. The lava is of basaltic composition and due to the relative poverty of silica little viscous. Occur lava fountains and curtains Depending on the present in the ascent of the lava pressure and its gas content. In effusive volcanic activity types of the plateau and the volcano shield volcano occur.
Prominent examples of effusive activity are the Hawaiian volcanoes Mauna Loa, Kīlauea and Mauna Kea. In the effusive activity of columns volcanoes there has been the occurrence of flood basalts repeatedly in the geological past, such as in the U.S. ( Columbia Plateau basalt ), Siberia ( Siberian Trapp ), India ( Deccan Traps ) or China ( Emeishan Traps ).