A range of possible reconciliations have been proposed, including leaky layering at 660 km, layering deeper in the mantle, or ubiquitous compositional heterogeneity like a 'plum pudding'.

Eco-Friendly vehicles have a minimum EPA-estimated mileage of 35 mpg combined and include hybrids, diesels and even a few fuel-sipping gas-only cars. May require specific trim level and/or ...