The cold rock from the ocean floor sinks deeper and deeper into the mantle, and once it reaches a depth of about 2,000km it pushes the hot blobs aside. When plates push into one another, the ocean floor is pushed down between them in a process known as subduction. These models are based on reconstructing the movements of tectonic plates. We used Australia's National Computational Infrastructure to run advanced computer simulations of how Earth's mantle has flowed over a billion years. However, we know tectonic plates and mantle plumes move over time, and research suggests the shape of the blobs is changing. One school of thought has been that the present blobs have acted as anchors, locked in place for hundreds of millions of years while other rock moves around them. However, how the blobs have changed over the course of Earth's history has puzzled them. Scientists generally agree the blobs are linked to the movement of tectonic plates at Earth's surface. We know the blobs are there because they slow down waves caused by earthquakes, which suggests the blobs are hotter than their surroundings. The mantle is solid but slowly flows over long timescales. The blobs are in the mantle, the thick layer of hot rock between Earth's crust and its core. In new research, we modeled a billion years of geological history and discovered the blobs gather together and break apart much like continents and supercontinents.

Scientists have known the blobs existed for a long time, but how they have behaved over Earth's history has been an open question. The blobs may also control the eruption of a kind of rock called kimberlite, which brings diamonds from depths 120–150km (and in some cases up to around 800km) to Earth's surface. When these plumes first reach the surface, giant volcanic eruptions occur-the kind that contributed to the extinction of the dinosaurs 65.5 million years ago.

They are thought to be the birthplace of rising columns of hot rock called 'deep mantle plumes' that reach Earth's surface. The blobs have their roots 2,900km below the surface, almost halfway to the center of the Earth.

Blob opera into the thick of it