Geology studies the Earth system. Our living planet owes its unique character to the interactions between geosphere (the solid earth), hydrosphere, atmosphere and biosphere. During geological time, the dynamics of the geosphere had an enormous impact on the evolutions within the other spheres and vice versa. The geologist is the expert of the subsurface and of the processes that take place in it. From this expertise, the geologist is armed to find solutions to social problems of the present and the future, such as climate change, scarcity of resources (water, ores, oil and gas), population pressure and migrations.