What methods do scientists use to predict volcanic eruptions? select all that apply

Observing changes in the shapes of volcanoes, measuring an increased incidence of earthquakes, measuring an increase in heat flow, and measuring an increased occurrence of gaseous emissions.

Explanation:

Volcanic eruption is the output of magma, pieces of rocks, gases and ash due to volcanism. Magma is made up of melted rocks and minerals due to the very high temperatures inside the Earth. Upon contact with the surface through volcanic eruptions, magma is called lava - which, when solidified over time, originates volcanic or magmatic rocks.

When a volcanic eruption occurs, the population that resides in the region can suffer serious damage, for this reason, scientists try to predict these eruptions so that the population can protect itself. Scientists can predict these eruptions by observing changes in the shapes of volcanoes, measuring an increased incidence of earthquakes, measuring an increase in heat flow, and measuring an increased occurrence of gaseous emissions

answer: 21

step-by-step explanation:

divide 630 by 30. 30 goes into 630 21 times

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