Geomagnetism is the study of the dynamics of the Earth's magnetic field, which is produced in the inner core. The Earth's magnetic field is predominantly a geo-axial dipole, with north and south magnetic poles located near the geographic poles that undergo periodic reversals and excursions.
Geomagnetism is the part of geology that looks at the dynamics of the Earth's magnetic field. These dynamics are produced by the Earth’s inner core. The Earth has two poles (North and South) which can undergo reversal and movement (excursions).
I believe studying the hydrosphere would be most important because we haven't explored a good majority of it yet so we need to explore our waters before we explore space
