One use case for optimistic locking is to have your application use the database to allow one of your threads / hosts to 'claim' a task. This is a technique that has come in handy for me on a regular basis.
Island arcs are volcanic islands that form parallel to ocean trenches in subduction zones. The Pacific Ring of Fire is home to many of these groups of islands. Volcanoes that form above hot spots like the Hawaiian islands are not volcanic arcs.Volcanic island eruption, USGS. Two oceanic plates converge. Islands form an arc when two oceanic plates converge creating a row of islands above the overriding plate.The older plate, which is heavier and denser, is forced beneath the lighter plate.he melting plate feeds magma chambers that supply volcanic islands that form an arc when the molten rock erupts onto the ocean floor of the overriding plate. Mariana Islands. Deep ocean trenches form between the converging plates.
Because the Pacific Plate is one of the faster moving plates, this type of volcanism produces linear chains of islands and seamounts, such as the Hawaiian-Emperor chain, the Line Islands, the Marshall-Ellice Islands, and the Austral seamount chain.