Sakurajima volcano
Sakurajima volcano |
|
||
| All fieldwork carried out on Sakurajima has been greatly helped by the kind assistance of Prof. K. Kamo, Prof. K. Ishihara, Dr M. Iguchi and the other staff of the Sakurajima Volcano Research Center. | |||
| Sakurajima volcano forms an island in Kagoshima Bay, southern Kyshu. In 1945, it was joined to the Osumi peninsula by a lava flow. The photo below, taken from Kagoshima, shows the Kagoshima ferry en route to Sakurajima on the opposite side of the bay. Sakurajima's frequent eruptions produce particle-laden plumes that commonly ascend several kilometers into the atmosphere. |  |
||
 |
|||
| The proximity of Sakurajima to Kagoshima Airport poses a hazard for internal and international aviation. Eruptions are closely monitored and the airport is kept informed of all activity. Much of the fieldwork carried out by Dr Jennie Gilbert and Dr Steve Lane on Sakurajima has been aimed at developing an electrostatic technique for detecting volcanic plumes. Like thunderstorms, most volcanic plumes are highly electrically charged and the perturbations of the natural atmospheric electric field they create can be detected. |  |
 |
Perturbations of the atmospheric electric field can be detected by measuring the electric potential gradient using the apparatus shown on the left. This monitoring site (located at Mochiki, on the southern flanks of the volcano) is one of twelve which have been employed. Data from the sensor at the end of the mast are recorded by a logger in the foil-covered box at the base of the apparatus.
In order to further understand the nature of the charge distribution within volcanic plumes, the charge held on falling ash particles can also be measured. The apparatus shown below separates falling particles by their polarity and allows charge measurements on either positively or negatively charged particles to be carried out. |
||
 |
|||