Petrographic properties of tephras of DSDP Leg 56 Holes

The investigation of volcanic ash near young source volcanoes is particularly helpful in enabling us to infer the history of volcanism in and around the island arcs. In the area of the Japanese islands volcanic deposits are usually distributed east of the source by prevailing westerly winds.

It is also possible that some deep sea tephra has its source in a large, already known land volcanism.