An eruption that boiled the sea
On May 9, 1988, the volcano known as Gunung Api—literally "Fire Mountain"—erupted violently. The eruption sent an ash plume soaring to an altitude of 16 kilometers and generated multiple pyroclastic density currents (PDCs). These are not simple lava flows; they are turbulent and superheated gas avalanches, ash, and rock fragments that can race across land at speeds exceeding 100 kilometers per hour.
What happened next is what makes this location exceptional for volcanologists. Instead of stopping at the coast, several of these PDCs plunged into the Banda Sea. Ordinarily, the immense cooling power of seawater would halt such a flow instantly. Here, however, the flows were so hot and fast that they created an insulating layer of steam upon hitting the water. This effect allowed the core of the pyroclastic current to maintain its terrifying speed and temperature, moving across the seafloor for more than a kilometer. The event was so intense that observers reported the sea surface boiling as the currents passed beneath. This phenomenon has only been well-documented at one other location on Earth, the Soufrière Hills volcano on Montserrat.
A new world on the seafloor
The underwater pyroclastic flows changed the submarine landscape. Once the eruption ceased, scientists mapping the seafloor discovered thick, widespread deposits of volcanic material, confirming the extent of the underwater flows. The currents had been devastating to the local marine ecosystem, burying and scalding a bright coral reef that had existed on the volcano's flanks.
The aftermath of this destruction, however, shows resilience. The new lava flows and pyroclastic deposits provided a fresh, stable substrate. Within just five years, scientists were stunned to find a diverse and thriving coral community had colonized the 1988 lava flows. This new reef supported 124 species of coral, with a coral cover of over 60 percent in some areas. Some individual coral colonies grew to over 90 centimeters in diameter in that short time. This rapid recovery has made the reefs around Banda Api a unique natural laboratory for studying how marine ecosystems can rebound after catastrophic events, bringing marine biologists and recreational divers to the area.