In 1963, a geophysicist named John Tuzo Wilson suggested that the islands, covered in layers of volcanic rock, overlie a magma plume formed when rock rises from the deep mantle and collects beneath the crust. This “hot spot” continually pushes to the surface, sometimes breaking through the tectonic plate, melting and deforming the surrounding rocks in the process. The plate shifts over millions of years while the magma plume remains relatively quiescent, creating new volcanoes on the plate and leaving dormant volcanoes behind. The result is archipelagos like the Hawaiian-Emperor Seamount chain and parts of the Island Plateau.
The hot spot theory gained widespread acceptance in the decades that followed. “No other theory can reconcile so many observations,” says Helge Gonnermann, a volcanologist at Rice University.
Some confirming observations came relatively recently, in the 2000s, after scientists began placing seismometers measuring terrestrial energy waves on the sea floor. John Orcutt, a geophysicist at the University of California, San Diego who helped lead this research, said the seismometers provided an X-ray image of the magma plume rising beneath Hawaii. The instruments were able to accurately read the direction and speed of magma flow; the results clearly indicated the presence of a hotspot.
This hot spot has probably fueled volcanic activity for tens of millions of years, although it only arrived at its current location below Mauna Loa about 600,000 years ago. And as long as it stays there, said Dr. Orcutt, it will reliably produce volcanic activity. “Few things on earth are as predictable,” he added.
Closer to the surface, it becomes more difficult to predict when, where and how intense these eruptions will be, despite the abundance of seismometers and satellite sensors. “The deeper you go, the smoother the behavior becomes,” said Dr. Orcutt. “Until this interface is formed between rock and molten rock and the ocean, the magma comes out rather sporadically.”