The 2,463-meter volcano has had eruptions described as phreatomagmatic
(magma and water driven) types since Monday, four lava fountainings as high as 500-700 meters above the summit and lava flows that cascaded down to the 6-km PDZ.
And then again at 12:45 pm there was what we call a phreatomagmatic
eruption wherein it produced an ash column about 10 kilometers high and it also produced what we call a pyroclastic flows around the volcano," said Paul Alanis, a science research specialist at the Philippine Institute of Volcanology and Seismology.
He said they expect more phreatomagmatic
eruption (combination of water and magma), in the coming days until the edifice goes back to the normal level.
According to (Casertano, Borgia, & Cigolini, 1983) both of these episodes were phreatomagmatic
where the 1910 eruption dispersed fine juvenile material in a single episode whereas the 1953 eruptions lasted several months with strombolian type activity, the creation of an intra-crateric dome by effusion of lava and the disappearance of the crater lake for a period of close to a decade.
The Volcano of Cancarix is an exceptional example of volcanic deposits characterised by phreatomagmatic
activity followed by lamproitic extrusion (Seghedi et al.
He connects phreatomagmatic
activity with a low magma flux during the initial stages of volcanism, where the vents are not open, or with a time of rapid readjustement and maar collapse.
Two papers study the evolution of the Santa Ana crater lake during 1992-2007, focusing on the 2006-2007 period when the lake drowned the eruptive vent following the 2005 phreatomagmatic
eruption, and test a GPS monitoring system on the site.
According to Wikipedia, geologists agree that Al Wahba Crater is classified as a Mr Crater which is caused by a phreatomagmatic
eruption-an explosion caused by groundwater coming into contact with hot lava or magma.
The crater was formed when a rising plume of magma encountered a pocket of underground water, resulting in a so called phreatomagmatic
Eruption styles falling into the first category include Strombolian, Vulcanian, and phreatomagmatic
activity, whereas those falling into the second include Hawaiian and Plinian activity.
For pyroclastic eruptions of magmatic or phreatomagmatic
origin, the high heat capacity and thermal conductivity of water leads to rapid heat transfer and potentially to another phase of fragmentation (Gudmundsson, 2003).
Key words: Bubble-wall texture, CIPW norm, ignimbrites, lava-domes, phreatomagmatic
eruptions, pyroclastic flows, modal compositions, normal composition, shards