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exotic terranes. In the Wrangellia paper, both geological evidence and paleo-
magnetic evidence were used, rather than only one or the other.
The Wrangellia terrane was defined in terms of geological criteria. It is
composed of Triassic-aged basalt that appears to have been formed deep
under the sea. More than 200 million years ago, enormous outpourings of
basalt quite similar in texture and composition to those making up the
Hawaiian Islands erupted from great submarine fissures. This basalt contin-
ued to burp out for many millions of years and eventually accumulated into
a mass of hardened lava many thousands of feet thick. Finally, in late Triassic
Present distribution of Wrangellia terrane.
