Amount of magma fragmentation and resulting dispersal of tephra (as...

Amount of magma fragmentation and resulting dispersal of tephra (ash and larger-sized particles) that typically accompanies different styles of eruption (for example, Hawaiian and Plinian). High fragmentation breaks or shatters the erupting magma into particles, including volcanic ash. Hawaiian-style eruptions do not fragment lava into ash-sized particles typical of larage Plinian-style eruptions (see photos above).

Interaction with water can cause magmas that would normally erupt lava flows to explode into ash particles, or cause normally explosive eruptions into more energetic eruptions. These eruptions are called phreatomagmatic eruptions (Surtseyan or Phreatoplinian, depending on height of eruption column and dispersal). For example, in 1886 Mount Tarawera in New Zealand produced a violently explosive basalt eruption because rising magma interacted explosively with shallow ground water. Substantial thicknesses of basalt ash from this eruption was consequently dispersed hundreds of kilometers downwind.