Science: The Theory of Suspect Terranes

A terrane is a piece of lithosphere, and every terrane has its own identifying characteristics. Every terrane contains rock and fossils different from those of bordering terranes. Also, at the boundaries of a terrane, there are major faults, and every terrane has different magnetic properties than those of the one’s around it. The theory of suspect terranes proposes that the continents are actually a collage of many different terranes put together. “Terranes that seem out of place geologically, called exotic or suspect terranes, are composed of pieces of plates that have broken off and then drifted great distances before attaching (accreting) to some other terrane or continental landmass” (http://pubs.usgs.gov/publications/text/Pangaea.html). Terranes travel along the ocean floor because of seafloor spreading, or the moving of the ocean floor. The terranes travel to a place where subduction is occurring, and as the continental crusted plate moves over the oceanic crusted plate, the terranes are pushed up off the sinking ocean floor and become part of the continent, or in some cases form mountains. Just to give you a general idea of how slow these terranes are actually moving; the terranes are like bumper cars, all moving independently, but the average speed that bumper cars goes is over 500 million times faster (http://pubs.usgs.gov/publications/text/Pangaea.html). Terranes have been found all over the world. A few of those terranes actually make up pieces of the west coast of the United States. A few major terranes in North America are the Sonoma terrane, the Alexander terrane, and the Wrangellia terrane. Scientists know these terranes have come from other parts of the world because certain minerals, rocks, and plant life not commonly found in the U.S. are being found on the shorelines of different continents than which these things all originated from. This means none other than the movement of terranes from far away places in order to get where they are. Thus, the theory of suspect terranes must be true.


1. USGS. “What Went On Before the Break-up of Pangaea?” 5 May 1999. .
2. Gould, Stephen Jay. “Capturing the Center.” Natural History. Dec. 1998.