"thermochemical piles come into sharper focus"
Ouch
Scientists have revealed new data about two giant blobs at the edge of the Earth's core, larger than continents and possibly older than any rock on the planet. Unlocking the mystery of the blobs, known as thermochemical piles, could help reveal clue about the Earth's formation, volcanic eruptions, and earthquakes. A team of …
The report says the blobs are denser than the surrounding Mantle, but also they transmit seismic waves slowly. But seismic waves travel *faster* in denser materials - that's how geophysicists calculate their density.
I suspect something has gone missing between the research and the press release.
What immediately came to mind was:
"We know for certain, for instance, that somewhere, sometime in the beginning there were hot lumps..." from Firesign Theatre "I think we're all Bozos on this bus"
Or could it be a secret lizard people atomic pile? Inquiring minds want to know!
Within largely homogeneous materials... the denser the material is, the faster sound will travel through it, but this only applies to specific types of material. The other big factor is the hardness of the material.
For instance, sound travels *much* faster through diamonds (~12000 m/s) or glass (~4500 m/s), than it does through lead (~2000 m/s).
This is why it's very difficult to image some types of material with seismic or ultrasonic waves, and where some of the difficulty in determining what the composition in the mantle might be. As far as velocity is concerned... warm iron and cool lead may look very similar.