coast of Proto-North America. Lime-rich rocks like limestone and marble become malleable under heat and pressure, and the collision squished and smeared them into the sinuous twists and turns of the Marble Valley. Thus, although the current climate and landscape of the Marble Valley do not even vaguely resemble the tropics, the presence of marble in the Northwest Highlands indicates that a tropical paradise once lay on the edge of Proto-North America. Western Connecticut was the Florida of the Paleozoic.

But what of the ocean (the Iapetos) that lay east of the carbonate bank? What happened to it? How was it disposed of, allowing the collision between Proto-North America and Avalonia to occur? An important feature that lies in the middle of the Iapetos Terrane helps explain this puzzle. But first we must digress into a little plate tectonic theory. When two continents start moving toward each other on a collision course, something must be done with all the oceanic crust that lies in between. Essentially, the ocean gets swept under the rug. Geologi- cally, this takes place in a "subduction zone ' " a deep slot in the Earth where oceanic crust is shoved underneath continental or other oceanic crust and into the Earth's mantle. Forced to accommodate a lot of unwanted material, the mantle melts the oceanic crust and sends some of it out again in the form of volcanos. Because of these earthly intestinal

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