Earthquakes are not easy to predict, but volcanic eruptions have more warning signals and instruments to measure those signals, therefore making them somewhat easier to forecast. the difficulty with predicting volcanic eruptions is a. height of the volcanoes b. number of volcanoes c. shortage of geologists d. cost of monitoring

D. Cost of monitoring

Explanation:

Despite the great concern and commitment of volcanologists, it is still not possible to predict exactly when a volcanic eruption will occur. However, some signs may be indicative of some upcoming activity.  Before an eruption, magma focuses on areas below the volcano, called reservoirs, where it moves producing vibrations, ie small earthquakes. This same movement can cause the slopes of the volcanic cone to collapse. As magma approaches the surface, it releases gases that can be detected in regions near the volcano.

The analysis of these gases allows to verify if there is variation in their quantity and composition. The movement of the magma, however, may not result in eruption. Instead, it can cool and solidify on the subsurface.

Since volcanoes typically come into operation at intervals of hundreds to thousands of years, they are not continuously monitored, even because this practice is costly (which makes monitoring difficult) and the same pattern is not always repeated in different eruptions.

However, when the volcano emits precursor clues, a major catastrophe can be prevented.

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