4.2 Conduction of terrestrial heat
Surveying shows that fissures and pocket of magma exist in the Changbai Mountain region,
which can provides a great deal of substance source and dynamic source stored up as huge heat
energy for volcanic activities. So geothermal anomaly often occurs in the region of modern
volcanic activity. Geothermal anomaly is the phenomena that underground temperature and
geothermal gradient increases much more in the area than its surroundings. Geysers and hot
springs are generally found in above regions. During the violent volcanic activities or forewarning
period of volcano eruption, abrupt geothermal anomaly comes out. Abrupt geothermal anomaly
means that underground temperature on some spots as well as the affected temperature of
surrounding area abruptly increases in a short time. Its geophysical properties represent time and
space features of current subterranean magma activity or crush movement intensity in the area,
which contains much information for geology, geophysics and geo-dynamics. So the above
information is very important to monitor and forecast temporary volcanic activity.
During the development of volcano, abrupt geothermal anomaly definitely occurs at repeated
times, however, pocket of magma detained at shadow crush is only the ideal spot hot source of
geothermal anomaly in volcanic region. Deep melting magma in the course of moving up by high
pressure excites pocket of magma. Therefore, the existed anomalous subterranean heat is aroused
into abrupt geothermal anomaly.
4.3 Convection of terrestrial heat
Most geothermal energy can be convected through the underground water and the magma
motion. When hot sticky magma suddenly touches cold circulation layers it will produce a great
deal of volatile flux and underground water will be heated. In addition, while volcano activity is
active, the temperature of original hot spring and crater lakes must be rising. In this case, heat
transmission in water body mainly depends upon heat exchange. Produced volatile flux and heated
gases such as vapor, hydrogen, HCL, CO 2 , CO, H2 S, SO2 , HF etc contained in magma and
adjoining rocks will be released to air through movement faults and broken rock cracks. They not
only bring heat to surface, but also result in the hothouse effect in basin and low gully, which will
make temperature rise in the area.
In summary, experiments prove that according to the above transmission mechanism, there is
an obvious increase for surface’s temperature in abrupt geothermal anomalous area in contrast to
geothermal normal area during the forewarning period of volcano activity. In the view of
formation cause and geothermal transmission mechanism of abrupt geothermal anomaly in regions
of volcano, rising range of temperature in anomalous area could be from 3 to 6 degree centigrade
or more. This offers a basic condition for monitoring volcanic activities by thermal infrared
remote sensing techniques.
5. Conclusion
Volcano monitoring involves the recording and analysis of volcano phenomena. The rapid
development of space technology offers scientists a good chance of conducting a serial of remote
sensing technique researches. Meteorology satellite as a popular surveying device is a ideal tool to
monitor abrupt geothermal anomaly during the forewarning period of volcanic eruption. Changbai
Mountain volcano located in Jilin Province has been studied by both chinese scholars and foreign
scientists for a long time. At present, except meteorology satellite monitoring, global positioning
system (GPS) is also used to monitor crust deformation behaved before eruption.
References
- You Yongxong et al, 1998. Monitoring earthquake’s forewarning field in the northwest of Yunnan Province by
remote sensing techniques. Science Press. p340-345 (in chinese)
-
Song Haiyuan et al, 1990. Study on the volcano geology of Changbai Mountain. Yanbian University Press (in
chinese)
- Jin Bolu et al, 1994. Study on volcanic geology of Changbai Mountain. Northeast Korean Nationality Education
Press p71-72 (in chinese)
