You may have wondered why we are drilling and sampling the sediments in this beautiful part of central Greece. The Gulf of Corinth is part of a continental rift system – where a tectonic plate is pulled apart and stretched. This is the first stage in the process that ultimately forms our oceans and ocean basins, such as the Atlantic Ocean, and has shaped the Earth’s surface that we know today. The rifting process causes the Earth’s crust and lithosphere to stretch and thin and the surface to subside. In the upper part of the crust the stretching and subsidence is taken up by fault structures which move during earthquakes every few hundred years. This creates a hole or basin which fills with sediments and water. In the Gulf we have up to 2.5 km of sediment and nearly 1 km of water. The Corinth Rift is only in the very first stage of rifting – where we are drilling, rifting only started about 1 or 2 million years ago. That may seem long for the non-geologist but is a fraction of the time it takes to form an ocean basin.
The reason we are working in this part of Greece is to understand the first stage of this process which is very well preserved here, particularly in the deep sea sediments of the Gulf of Corinth. By sampling the sediments we can determine their age, and from that we can tell how fast the faults slip, and when and how fast the basin opened and subsided. Knowing how fast the faults are moving will also help us understand better their earthquake-generating potential in this very seismically active region. We can also see how basin formation and the climate of the area caused sediments to be eroded and transported into the basin.
If you are interested in learning how the environment of the basin changed, please also take a look at the post from Clint Miller on “Sea Level Change” which tells you about how the basin has been affected by sea level change and tectonics. Also take a look at the post from Rob Gawthorpe “Onshore from the Offshore Perspective” to see how the rift faults have affected the shores of the Gulf of Corinth.
View east along the southern shore of the Gulf of Corinth, near Aigion, showing the topographic effects of the rift faulting. The hills to the right are uplifted whilst the Gulf to the left subsides.
Cartoon showing how the Earth’s lithosphere (the tectonic plate) and the crust thin during stretching. The upper crustal stretching is generated by movement on faults. The fault movement and crustal thinning cause subsidence which create the water and sediment filled basin of the Gulf of Corinth.