Alcatel Submarine Networks (ASN) is a provider of turnkey undersea network solutions. Tsunamis can cause catastrophic coastal flooding, most commonly resulting from undersea earthquakes. A line of undersea volcanoes extends out along the Kermadec Ridge. The European road E10 connects the larger islands of Lofoten with bridges and undersea tunnels. Younger deposits at middle altitudes include pillow lavas, the product of undersea volcanic eruptions. Submarines are also used in tourism and undersea archaeology. It represents the world's deepest undersea immersed tube tunnel. China is researching various types of air, land, sea, and undersea autonomous vehicles. Some even speak about a Black Sea undersea river. Testing involves blasts of noise which echo off the undersea rock formations. Closed bells are often used in saturation diving and undersea rescue operations. The destroyer provides defense against surface, airborne and undersea threats. Sage was thrilled by the idea of traveling by an undersea tunnel. Both expansions were made possible by advances in overland telegraphs and undersea cables. As of 2013, Aberdeen remained a major world centre for undersea petroleum technology.