139. United Plates of America (1988)

United Plates of America

Plate tectonics emerged as the unifying theory for the evolution of Earth’s lithosphere in the mid-1960s. At the outset, the emphasis was on explaining the motion of the present-day continents over the last 600 million years of Earth history.

Whether plate tectonic processes operated in deeper geological time such as the Precambrian and, if so, how they differed from the subsequent Phanerozoic, remained open questions. And these were obviously of great interest to Geological Survey of Canada scientists charged with mapping and interpreting the geological history of the Canadian Shield.

In 1988, Survey geologist Paul Hoffman, drawing on two decades of work with numerous colleagues and students, published a masterful synthesis of the tectonic history of the North American Craton. Laurentia, as he called it, is a collage of at least six juxtaposed Archean provinces, older than 2.5 billion years and sutured by orogenic belts about 1.8 to 2.0 billion years ago. The weight of evidence suggests processes of subduction and collision very similar to those ongoing today.

Category: Science Advances

Decade: 1980s


Hoffman, P.F., 1988. United Plates of America, The Birth of a Craton: Early Proterozoic Assembly and Growth of Laurentia; Annual Review of Earth and Planetary Sciences, v. 16, p. 543–603. doi:10.1146/annurev.ea.16.050188.002551

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