According to one hypothesis, these features may form at the site of impact events that penetrate the oceanic crust, while in another hypothesis, they are the result of lithospheric extension leading to the passive upwelling of fertile melt.
The distribution spectrum of these features has peaks at harmonic degrees 2 and 6 that are strongly correlated with the long-wavelength residual geoid. These features are used as a reference frame for calculating true polar wander, and they contain unusually high ratios of helium-3 to helium-4. According to one hypothesis, these features may form at the site of impact events that penetrate the oceanic crust, while in another hypothesis, they are the result of lithospheric extension leading to the passive upwelling of fertile melt. These features create namesake (*) "tracks" that may contain kimberlite fields. W. Jason Morgan proposed the most widely accepted theory of their formation, in which flood basalts and these features represent the heads and tails of mantle plumes, respectively. For 10 points, name these geologic features located far from tectonic plate boundaries that underlie volcanic chains like the Hawaiian Islands.
The distribution spectrum of these features has peaks at harmonic degrees 2 and 6 that are strongly correlated with the long-wavelength residual geoid.
hotspots [prompt on "mantle plumes"]