The 1980 eruption of Mount St. Helens in Washington, which ripped apart the volcanos summit, was a Plinian eruption of Volcanic Explosivity Index (VEI) 5. The strongest types of eruptions, with a VEI of 8, are so-called "Ultra-Plinian" eruptions, such as the one at Lake Toba 74 thousand years ago, which put out 2800 times the material erupted by Mount St. Helens in 1980. Hekla in Iceland, an example of basaltic Plinian volcanism being its 1947–48 eruption. The past 800 years have been a pattern of violent initial eruptions of pumice followed by prolonged extrusion of basaltic lava from the lower part of the volcano. Pinatubo in the Philippines on 15 June 1991, which produced 5 km3 (1 cu mi) of dacitic magma, a 40 km (25 mi) high eruption column, and released 17 megatons of sulfur dioxide. Kelud, Indonesia erupted in 2014 and ejected around 120,000,000 to 160,000,000 cubic metres (4.2×109 to 5.7×109 cu ft) volcanic ashes which caused economic disruptions across Java. Phreatomagmatic eruptions
Phreatomagmatic eruptions are eruptions that arise from interactions between water and magma. They are driven by thermal contraction of magma when it comes in contact with water (as distinguished from magmatic eruptions, which are driven by thermal expansion). This temperature difference between the two causes violent water-lava interactions that make up the eruption.
Smooth Muscle Hypercontractility
At a cellular level, pathways that lead to enhanced myosin light chain phosphorylation promote vasoconstriction. Increased activity of Rho-kinase leading to enhanced myosin light chain phosphorylation has been implicated in the pathogenesis of coronary vasospasm. Diagnosis
There are no set criteria to diagnose coronary vasospasm. Thorough history taking by a clinician can assist in the diagnosis of coronary vasospasm. In cases where symptoms of chest pain are present, identifying features that distinguish episodes of vasospastic angina from traditional angina can aid in the diagnosis. Features such as chest pain at rest, a diurnal variation in tolerance for exercise with a reduction in tolerance for exercise in the morning, and responsiveness of chest pain to calcium channel blockers as opposed to beta blockers can be important clues.EKG can occasionally be used to diagnose episodes of coronary vasospasm. However, relying on EKG is not always possible due to the transient nature of coronary vasospasm episodes. Due to the challenge of capturing episodes of coronary vasospasm spontaneously, provocative testing to induce coronary vasospasm during coronary catheterization can be used to make the diagnosis. Provocative testing relies upon the use of pharmacological agents that promote or trigger episodes of vasospasm. Agents commonly administered include ergonovine and acetylcholine. Both pharmacological agents have vasoconstrictive effects on coronary arteries. However, in the clinical setting, provocative testing is not routinely performed. The reason for this is due to the adverse effects of these pharmacological agents.