In 1963, a geophysicist named John Tuzo Wilson proposed that the islands, covered with layers of volcanic rock, sit atop a magma plume, a phenomenon that occurs when rock in the deep mantle bubbles up and Formed when the crust below pools. This “hot spot” is constantly pushing toward the surface, sometimes breaking through tectonic plates while melting and deforming the surrounding rock. The plates moved over millions of years while the magma plumes remained relatively stationary, forming new volcanoes on top of the plates and leaving inactive volcanoes in their wakes. The result is archipelagos such as the Hawaii-Emperor seamount chain and parts of the Icelandic plateau.
The hotspot theory gained broad consensus in the ensuing decades. “No other theory can reconcile so many observations,” says Rice University volcanologist Helge Gonnermann.
Some confirming observations came only recently, in the 2000s, after scientists began placing seismometers on the ocean floor that measure energy waves on the surface. Seismographs provided X-ray pictures of the magma plume rising beneath Hawaii, said UC San Diego geophysicist John Okut, who helped lead the study. These instruments were able to accurately read the direction and speed of magma flow; the results clearly pointed to the presence of hot spots.
This hotspot may have fueled volcanic activity for tens of millions of years, though it only reached its current location beneath Mauna Loa about 600,000 years ago. As long as it’s still there, Doctor. It will reliably generate volcanic activity, Orcutt said. “Almost nothing on Earth is predictable,” he added.
Closer to the surface, predicting the timing, location and magnitude of these eruptions becomes more difficult, despite the abundance of seismographs and satellite sensors. “The deeper you go, the smoother the behavior,” says Dr. Alcatel said. “When you look at the interface between rock, lava and ocean, magma tends to spew out occasionally.”