GEOLOGY

Detailed explanation-1: -Active volcanoes have a recent history of eruptions; they are likely to erupt again. Dormant volcanoes have not erupted for a very long time but may erupt at a future time. Extinct volcanoes are not expected to erupt in the future. Inside an active volcano is a chamber in which molten rock, called magma, collects.

Detailed explanation-2: -Mauna Loa erupted most recently in 1984, and will erupt again in the future, posing significant risks to people living on the flanks of the volcano.

Detailed explanation-3: -Sixty percent of all active volcanoes occur at the boundaries between tectonic plates. Most volcanoes are found along a belt, called the “Ring of Fire” that encircles the Pacific Ocean. Some volcanoes, like those that form the Hawaiian Islands, occur in the interior of plates at areas called “hot spots.”

Detailed explanation-4: -Eruptions can be as short as one day, or can erupt for hundreds of years. Active volcanoes are those that have the potential to continuously erupt. Once a volcano becomes active, it takes an average of ten years for the eruption to finish.

Detailed explanation-5: -An increase in the frequency and intensity of felt earthquakes. Noticeable steaming or fumarolic activity and new or enlarged areas of hot ground. Subtle swelling of the ground surface. Small changes in heat flow. Changes in the composition or relative abundances of fumarolic gases.