In this chapter, very brief scenarios of the complex interaction of solar radiations with the Earth’s magnetosphere are presented and the intricate origin of the (i) sferics, (ii) pulsations and micropulsations, (iii) variations of the extraterrestrial magnetic fields, (iv) Van Allen Radiation belts, (v) ionosphere, (vi) ring current, (vii) magnetopause, (viii) magnetic sheath, (ix) magnetotail and (x) magnetic storms are discussed. The various branches of geophysics, evolved because of this time varying natural source electromagnetics, are also discussed in reasonable detail. They are (i) telluric current methods (T), (ii) magnetotellurics (MT), (iii) audiofrequency magnetotellurics (AMT), (iv) geomagnetic depth sounding (GDS), (v) magnetometer array studies (MA), (vi) magneto-variational sounding (MVS), marine MT (MMT) and (vii) the audio-frequency magnetic method (AFMAG). A few controlled-source auxiliary tools that are used along with MT and AMT are: (i) controlled-source audio-frequency magnetotellurics (CSAMT), (ii) long/offset transient electromagnetics (LOTEM), (iii) marine controlled electromagnetic (CSEM) and radiomagnetotellurics (RMT). Brief discussions on mathematical modelling and inversion are included to touch upon the interpretational aspects of geophysical data. <...>

Natural hazards are associated with land, ocean and atmospheric processes, and their impacts on human societies. Over the years, the interactions between land, ocean, biosphere and atmosphere have increased, mainly due to population growth and anthropogenic activities, which have impacted the climate and weather conditions at local, regional and global scales.

Much near-surface geophysics research and development has occurred since the announcements in early 1988 in GEOPHYSICS and THE LEADING EDGE that Stanley H. Ward was assembling a collection of papers for a new book tentatively titled Environmental Geophysics. The resulting 71 published papers filled three hardbound volumes—Review and Tutorial; Environmental and Groundwater; and Geotechnical.