1.   Hess mistakenly thought that the oceanic crust consisted of altered peridotite, the material of the mantle itself.

2.   Its purpose is to gather sufficient information to answer questions about magma chambers in oceanic crust.

3.   According to this idea, oceanic crust and sediment are subducted into the deep mantle to rise again as mantle plumes hundreds of millions of years later.

4.   From these observations, Hofmann and I proposed that plumes consist in part of deeply subducted oceanic crust and sediment.

5.   The initial estimate was based partly on the time required for radioactive heating to cause the subducted oceanic crust and sediment to become buoyant and rise.