Peter J. Smith Department of Earth Sciences Open University Milton Keynes, U.K.
The concept of hotspots linked to rising mantle plumes has been so successful in explaining some intraplate volcanic phenomena (such as volcanic island chains) and topographic swells that there has been a tendency to assume that it can explain all of them. However, igneous activity/uplift does not always quite fit the theory. For example, the Bermuda and Appalachian-Labrador rises have trends almost perpendicular to the predicted hotspot tracks. In these and other cases, the observed phenomena are much more likely to be related to the convective geometry of the mantle.
P.R. Vogt, "Bermuda and Appalachian-Labrador rises: Common non-hotspot processes?" Geology, 19, 41-4, January 1991. (Naval Research Laboratory, Washington, D.C.)
Volcanically generated glass shards as large as 300 <109> have been found in a section of Greenland ice core about 70,000 years old. These particles are much larger than anyone...109>