In the past it was thought that the boundary between continental and oceanic crust at the edge of the ocean basins was close to the edge of the flat “abyssal plains”, but over the past 20 years it has been revealed that true oceanic crust is often not present until much further out into the ocean, and that in between there can be regions up to 100-150 km wide where no crust at all is present.  Tim Minshull from G&G has just published a paper in the Journal of Geophysical Research, exploring one such region west of Portugal using seismic data.   A new analysis of these data shows that the region includes a 70 km wide zone of ridges made of mantle rocks that run parallel to the edge of the continent, and that within this region there are linear magnetic anomalies that would normally be interpreted to indicate the presence of oceanic crust.

To read the full paper click here.