Although the Earth’s oceans as we see them today are several thousand kilometres wide (for instance around 6 000 km for the Atlantic Ocean), their history began with fractures and basins that were far smaller in size. The initial phase preceding their formation is called rifting, or continental rupture, since an ocean in fact results from the break-up of a continent. Understanding this process is of key importance for a number of reasons that involve several scientific fields.
Firstly, at a fundamental level, it makes it possible to study the ways in which new tectonic plates are created. However, rifting also leads to the emergence of basins and therefore determines the location of resources that have always been of value to humans, such as water, minerals, fossil fuels and geothermal energy. In addition, the faults associated with rifting constitute topographical barriers that impact population dynamics. And finally, the accompanying seismic and volcanic activity is a source of risk that has to be managed by local communities. Most of today’s ocean basins are too mature to allow direct access to this initial phase of formation.