Explain how earthquakes and volcanic eruptions can be monitored and predicted

The study of plate tectonics has meant that seismologists can now very accurately predict where earthquakes will occur – it’s when they will occur that’s difficult to pinpoint. It is well known that major earthquakes occur at plate boundaries, especially convergent boundaries where two plates collide, or transform boundaries where two plates slide past each other. Japan, for example, is a major earthquake zone because it is on the boundary of three major plates. The San Andreas Fault in California is another boundary where earthquakes regularly occur, albeit a transverse one. Seismologists have mapped the recent earthquakes along the fault and can accurately predict where the next earthquake will occur, they just don’t know when. The bigger the time gap since the last earthquake, the more convergent the next one will be.

Seismologists use modern technology to monitor earthquake activity along fault lines. Lasers and tiltmeters are used to monitor changes along the fault. Scientists use seismometers to study the tremors along the fault lines. Water and oil levels in wells are also closely monitored for sudden changes that might mean that the ground is under pressure. Radon gas levels are measured because any sudden increase in radon gas levels means rocks are fracturing underground. In China, changes in animal behaviour have been observed in the past and claim to be early warnings for earthquakes.

Like earthquakes, volcanoes also occur most often at plate boundaries. The more convergent volcanoes tend to occur at convergent boundaries. It is a lot easier to predict where volcanoes will occur as they are very active in the days preceding an eruption. Even dormant volcanoes are kept under strict observation and any changes are monitored using modern technology.

Before volcanoes erupt there are many obvious signs. A gradual or sudden swelling of the magma chamber in the volcano is a sign of the magma moving upwards through the vent into the cone. This was very clear to see before Mt St Helens erupted in 1980. Lasers can very accurately monitor these changes in the shape of volcanoes. In addition, there is also a significant increase in the emissions of sulphur dioxide before an eruption. This is a sure sign of major volcanic activity as it shows that more magma is rising near to the surface. Finally, the use of seismometers is key to monitoring volcanoes as tremors before an eruption are giveaway signs of magma moving up through the crust.