The eruption style ranged from effusive—mildly explosive at the Duraznero and Llano del Banco vents—to mildly explosive at the Hoyo Negro vent and was strombolian in style. It is classed as having a Volcanic Explosivity Index (VEI) of 2. Earthquakes The process creating the earthquakes of 1 and 2 July is considered to have been driven by the pressure caused by the rising magma super-heating water trapped within the edifice of the volcano. It is unlikely that the trapped waters could vapourise due to being under considerable pressure. What is postulated is that the waters were heated to a point where they could not absorb further thermal energy in the available space. Continuing heating required the water to expand further and the only way it could do so was to move the flank of the volcano. This caused the two earthquakes that were reported as occurring during the eruption along with the development of the crack. That the water entrapped within the edifice did not vapourise is shown by the absence of phreatomagmatic explosions except the mildly explosive eruptive activity that occurred at the Hoyo Negro vent from 12 to 22 July: steam escaping explosively from the ground is often a precursor of volcanic activity. Further evidence that vapourisation did not occur is that when Rubio Bonelli visited the rift the following day, the newly opened fissure "... Was not issuing fumes, vapour, steam, ashes, lava or other materials ..." In fact at no time during or after was steam or phreatomagmatic activity reported. This reinforces the claim that the waters trapped within the edifice never vapourised, which they would do if the pressure had fallen sufficiently to allow the super-heated water to flash into steam. Only at the Hoyo Negro did any phreatomagmatic activity occur. Unlike the northern sector of the island, the Cumbre Vieja is "dry." Unlike the northern sector there are no water galleries, and it is therefore unlikely that the earthquake was caused—as claimed by Day et al.; by water becoming superheated by rising magma. Research is continuing. Due to the lack of seismic monitoring equipment on the island, any claims about seismic activity are based upon personal observation and may not be reliable. 1971 eruption The 1971 eruption occurred at the southern end of the Cumbre Vieja at the Teneguía vent. The eruption was mainly strombolian in style. Lava was also erupted. Seismic activity did