17. Question: Have ancient trenches ever been found?
Response: The Franciscan terrane in California, as was mentioned in my response to question 4 above, is a classic example of a fossil subduction zone complex that has been in the geology literature for the past 40 years. With only a short drive north of San Francisco, one can inspect these rocks first hand. Similar fossil subduction zones containing high grade metamorphic blueschist rocks have been described in Greece, Turkey, Japan, New Zealand, and New Caledonia east of Australia. Another such example mentioned in my response to question 5 above is the North Motagua Fault Zone in Guatemala. There are dozens of other spectacular examples well documented in the standard literature.