Geophysics; which is also known as Geophysical Science, is a subject with a broad spectrum of applications. Found at the intersection of many of the major sciences including physics, mathematics, planetary science, geology, oceanography and glaciology it can be defined simply as the application of physics and mathematics to the study of the planet or any planet in our solar system; or any other.
Classically, geophysics has concerned itself with the nature of the physical occurrences at and below the surface of the earth including, as stated above in part, geology, oceanography, geodesy, seismology, hydrology, etc. however; practically, it includes many methods, techniques and concepts which are vital economically to our civilisation. Some of these essential roles include:-
-Searching for traditional fossil fuels and mineral resources;
-Assessing the viability of potential locations for offshore wind farms, or other civil engineering projects;
-Environmental monitoring including the monitoring of nuclear test-ban treaties;
-Assessing and mitigating natural hazards such as earthquakes and volcanoes;
-Finding solutions to waste management such as the sequestration of carbon dioxide from the atmosphere;
-Characterizing and protecting the world's water resources;
-Investigating archaeological sites.
It is a subject with such breadth of scope that it enables us to pose and attempt to answer fundamental questions concerning our planetary system and solar system. By doing so we should be able to uncover the driving forces behind such phenomena as the evolution of ocean currents and atmosphere, or the interaction between the planet's magnetic field and the solar wind. It concerns some of the most violent of phenomena from earthquakes and volcanic eruptions capable of causing thousands of deaths to the birth and destruction of entire planets. In application; seismic waves from earthquakes are used to identify and map the Earth's crust, mantle and core. as the data compile can tell us about stresses within our planet, and about the evolution of geological faults.
The science also studies some of the more gentle geophysical occurrences including the movement of tectonic plates at the Earth's surface by only centimetres per year, the movement of the direction in which the compass needle points by hundredths of degrees per year or the gradual rise of land once covered by ice sheets. Again in application; small differences in gravity over the Earth's surface are caused by density variations beneath. We can analyse electrical currents flowing inside the Earth, and its magnetic field. We use ancient magnetic fields recorded in rocks to map the past motion of continents, and study the deep causes of this motion.
All these processes are in some way related to each other, and therefore require study from the most minute scale to a planetary scale, It is this interaction an the time involved for these processes to take place which makes geophysics so exciting and challenging.