Seismic observations are made using seismographs deployed near volcanic areas, watching out for increased seismicity during volcanic events, in particular looking for long period harmonic tremors which signal magma movement through volcanic conduits.
Surface deformation monitoring includes the use of geodetic techniques such as leveling, tilt, strain, angle and distance measurements through tiltmeters, total stations and EDMs. This also includes GNSS observations and InSAR.
Surface deformation indicates magma upwelling: increased magma supply produces bulges in the volcanic center's surface.
Gas emissions may be monitored with equipment including portable ultra-violet spectrometers (COSPEC, now superseded by the miniDOAS) which analyzes the presence of volcanic gases such as sulfur dioxide; or by infra-red spectroscopy (FTIR)
Increased gas emissions, and more particularly changes in gas compositions, may signal an impending volcanic eruption.
Temperature changes are monitored using thermometers and observing changes in thermal properties of volcanic lakes and vents which may indicate upcoming activity.
Other geophysical techniques (electrical, gravity and magnetic observations) include monitoring fluctuations and sudden change in resistivity, gravity anomalies or magnetic anomaly patterns which may indicate volcano-induced faulting and magma upwelling.
Stratigraphic analyses includes analyzing tephra and lava deposits and dating these to give volcano eruption patterns, with estimated cycles of intense activity and size of eruptions.
Volcanology has an extensive history. The earliest known recording of a volcanic eruption may be on a wall painting dated to about 7000 B.C.E. found at the Neolithic site at Çatal Höyük (now known as Çatalhöyük), in Anatolia, Turkey. This painting has been interpreted as a depiction of an erupting volcano, with a cluster of houses below shows a twin peaked volcano in eruption, with a town at its base (though archaeologists now question this interpretation .
The volcano may be either Hasan Dağ, or its smaller neighbour, Melendiz Dağ.
More than 250 flights to and from the United Kingdom are cancelled Thursday due to the volcanic ash that has drifted over Europe following a volcanic eruption in Iceland. All of British Airways' domestic flights, as well as flights in Norway and northern Sweden were halted. Aberdeen, Glasgow and Edinburgh, Scotland airports were all shut.
Following advice frm the Met Office, the National Air Traffic Service has reduced restrictions to UK airspace this morning as a result of volcanic ash drifting across the United Kingdom from Iceland," said British airport operator BAA.
Irish, Finnish and Spanish airports have all followed suit.
The drifting ash can damage aircraft engines and it has also clouded visibility.
A volcano on the Eyjafjallajokull glacier in southern Iceland erupted on Wednesday, causing evacuations in the immediate area.
