Читать книгу Biogeography in the Sub-Arctic - Группа авторов - Страница 17

Masses of mantle rock rise convectively when their composition and/or temperature confers buoyancy. Temperature, however, is regarded as the dominant factor and great volumes of abnormally hot rock are thought to detach periodically from deeper parts of the mantle to rise as so‐called mantle plumes. Although the concept of mantle plumes dates back to the early 1970s, it remains controversial with opponents of the idea referring simply to foci of high temperature phenomena as ‘hot‐spots’ and denying that such plumes arise from the deep mantle (e.g. Anderson 2005).

The idea that mantle plumes have a mushroom‐like shape, with a massive plume head and an extremely hot tail, is based on fluid‐dynamical studies. The most voluminous magmatic events during the Earth's history have been related in space and time to an impact at the base of the lithosphere by such a plume head. Such a ‘hot‐spot’ model was outlined for the North Atlantic by White (1988), postulating a central plume causing raised asthenospheric temperatures across a wide region. A review of conflicting hypotheses with respect to the North Atlantic by Meyer et al. (2007) concluded that it would be difficult to present a model explaining both the records of igneous activity and associated uplift (discussed below) without appealing to an up‐rise of hot mantle beneath the lithosphere. Because the various arguments cannot be rehearsed in this chapter the author adopts a partisan attitude, regarding the plume model as the more robust and better supported by evidence.