Seth Stein and coworkers are investigating plate boundary processes and deformation within the lithosphere using a range of techniques including seismology, and marine geophysics. Our current focus is on one of the most important processes shaping our planet – the breaking apart of continents to form new oceans. Throughout earth’s history, continents have split along rifts, long zones of volcanism and stretching, which become spreading centers along which new ocean basins form and can grow to the size of the Atlantic and Pacific. To explore these issues, we are studying the spectacular 1.1 billion year old Mid-Continent Rift (MCR). The rift failed, leaving a 3000 km long belt of volcanic and sedimentary rocks left from the early rifting stage. This fossil rift has two major arms meeting in the Lake Superior region. One extends southwestward at least as far as Oklahoma, and the other extends southeastward through Michigan to Alabama. We are also examining passive continental margins, like those on either side of the Atlantic, to see how structures there compare to those on the MCR.