the metamorphic rock is there in the first place because the Uplands are the collision terranes. Thus, stone walls say almost as much about continental collisions as they do about the problems of colonial agriculture.

Long threads of history connect terranes to landscape and to land use. To truly understand the extent to which terranes have influenced glacial deposits, the positioning of rivers, the routing of roads, the location of good farmland, the availability of water power, and the construction of colonial churches, a more detailed explanation of terranes is required. Because Connecticut has so much time and space compressed into so little, the evidence needed to connect landscape and land use to terranes is, unfortunately, rather complex. But it is worth plowing through some of this evidence, for two reasons: first, to understand how geologists have determined the identities of the terranes and arrived at the story of the collision, and second, to be able to trace the threads of time from the present into the deep past.

The Three Collision Terranes

Identifying terranes in the Pangaean crunch-zone resembles the task of state troopers investigating a multi-car traffic accident. Each Collision terrane is a crumpled car in a big pile-up, rock twisted and folded by the impact. The object is to figure out where one terrane ends and the next begins, what type of car each terrane was, which direction it came from, and how fast it was moving. Three things confound the investigation. First, the towtrucks of Pangaea's break-up have already hauled away some of the cars, making the reconstruction of their role in the collision more difficult. Second, the accident took place millions of years ago and erosion has deeply rusted the terrane-cars, removing much of the evidence of manufacturer and model. And third, there were no witnesses.

Despite the uncertainties inherent in an investigation of this sort, several lines of evidence still can be followed. One of the most important

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