There’s very little known about the home of the blobs – the core-mantle boundary (CMB) – but it’s likely that this thermal crypt is often the final resting place of large segments of snapped off tectonic plates that have slipped underneath less dense tectonic plates in a process known as subduction. If a tectonic plate fragment impacts the CMB, it might push vast amounts of molten material up to the surface as a plume.
Alternatively, it might just stay down there and slowly decompose and dissolve. As the authors of the study suggest, it is possible that this second scenario is what created the gigantic blobs.
Bizarrely, though, seismic data indicates that they are definitely more molten than the mantle nearby. Descending tectonic plate fragments are normally cooler than the mantle, so the fact that these blobs are actually hotter indicates that they are made of something different to modern-day tectonic plates – a rock composition that has retained heat longer than the current mantle is able to.
So one possibility is that they could be the remnants of ancient and chemically distinct tectonic plates. Stranger still, the fact that they are hotter than their surroundings means that they should be rising upwards. After all, hotter materials are less dense and more buoyant than their surroundings, but seismic data suggests they aren’t yet mobile.
If, however, they did begin to rise, the implications are troubling. Their vast size suggests that they could each form a “superplume”, one that would breach the crust and create massive eruptions that would last for millions upon millions of years – and not a single geophysicist on Earth knows when this process may begin to happen.
You could argue that the mantle, the large red-colored layer depicted here, is more mysterious to scientists than deep space. Vadim Sadovski/Shutterstock