The blobs are in the mantle, the thick layer of hot rock between Earth’s crust and its core. The mantle is solid but slowly flows over long timescales. We know the blobs are there because they slow down waves caused by earthquakes, which suggests the blobs are hotter than their surroundings.
Scientists generally agree the blobs are linked to the movement of tectonic plates at Earth’s surface. However, how the blobs have changed over the course of Earth’s history has puzzled them.
One school of thought suggests that the present blobs have acted as anchors, locked in place for hundreds of millions of years while other rock moves around them. However, we know tectonic plates and mantle plumes move over time, and research suggests the shape of the blobs is changing.
