Do mantle plumes exist?  

This is a nice current issue in the Earth sciences so I thought I'd bring it up. From what I've read there are some serious doubts as to the validity of the mantle plume hypothesis. It was initially proposed to explain "hot spots" like Hawaii, where there is volcanism that is not (at first glance) explained by plate tectonics.

Some seismologists have claimed they have imaged the plumes, but others have discarded their claims; the data is noisy and depends upon certain estimated values for some variables. As far as I am aware the most current data from the geochemists is now begining to mount up against the plume theory.

Having said that, the plume theory is quite simple and to me at least seems intuitively elegant enough that it could just be right, especially when viewed in conjunction with the experimental evidence of fluid mechanics showing that thermal and compositional convection can lead to plume structures developed at interfaces.