Paleorifts — Concluding Remarks

it is not yet clear if continental rifting occurs in response to one or more causal mechanisms. However, evidence exists that at least some of the rifts in areas affected by plate-to-plate interactions have formed over sublithospheric thermal anomalies. All present hot spots identified on the North American and Eurasian plates (not falling near or on spreading ridges) lie in areas of high seismic activity on the continental side of collision type or transform plate boundaries. It is suggested that when a plate passes over a thermal anomaly of sufficient magnitude, the chances of this thermal anomaly causing penetrative magmatism and rifting, are greatest in those parts of the plate which is already under tension.