Monitoring volcanoes
\nPicture
\nAbove is a seismogram which is what is drawn to show the strength of earthquakes
\nThe eruption of Mount St. Helens was expected and prepared for, but in spite of the monitoring that had taken place, the exact date and time of the eruption took people by surprise.<\/p>\n
There are some signs to look out for:
\nEarthquakes are a frequent sign of an impending eruption and their frequency and strength can be recorded
\nBulging on one side of the volcano – the swelling is obvious and a clear sign of magma moving
\nTiltmeters can identify small, subtle changes in the landscape
\nGlobal Positioning Systems (GPS) use satellites to detect movement of as little as 1mm
\nSatellites can detect changes in surface temperature
\nDigital cameras can be used to check for changes in volcanic activity
\nGases being emitted from the vent change before an eruption
\nRobots called ‘spiders’ are often deployed to look inside the rim of the volcano
\nThe past frequency of eruption is often investigated: the gap between eruptions and the pattern of lava flows, ash movement and lahars can tell people about how the volcano is likely to behave
\nThis technology allows people to prepare for an eruption by organising the evacuation of people and arranging supplies.
\nPicture
\nAbove is a seismograph which draws the seismogram in the first picture<\/p>\n","protected":false},"excerpt":{"rendered":"