Lōʻihi is the youngest volcano in the Hawaiian chain, a massive structure growing submerged beneath the Pacific Ocean about 20 miles (30 km) southeast of the Big Island of Hawaiʻi. Its Hawaiian name means “Long One,” a reference to its elongated shape. The volcano is classified as a seamount, a mountain rising from the seafloor that does not reach the water’s surface. As the next anticipated island, Lōʻihi provides scientists with a unique opportunity to study the youthful, submarine stage of Hawaiian volcano formation.
Current Depth and Activity Status
The summit of Lōʻihi, recently renamed Kamaʻehuakanaloa, currently rests about 3,200 feet (975 meters) below the ocean’s surface. Despite being submerged, the volcano is remarkably tall, rising over 10,000 feet (3,000 meters) from the seafloor. This makes Lōʻihi higher than many mountains on land.
Lōʻihi is an active submarine volcano, evidenced by frequent seismic activity and the presence of fresh lava flows. The seamount generates periodic earthquake swarms, with the most energetic recorded event occurring in 1996. This seismic burst involved over 4,000 earthquakes and led to the collapse of part of the summit, forming a new pit crater named Pele’s Pit.
The summit area contains low-temperature hydrothermal vents, which discharge mineral-rich heated water. Observations show the summit is covered in glassy pillow-lava flows, indicating recent volcanic activity. These vents and fresh lava flows confirm that Lōʻihi is dynamically growing, tapping into the same deep magma source that feeds Kīlauea and Mauna Loa.
Understanding the Growth Rate
Hawaiian volcanoes grow through effusive eruptions, where lava flows gently from the vents. Deep beneath the ocean, the lava cools rapidly into characteristic bulbous forms known as pillow lavas, which stack up to build the massive shield structure. This slow, continuous process means the growth of Lōʻihi is not a simple, linear progression.
A major challenge in predicting the emergence timeline is the occurrence of massive flank collapses, which are a common feature of Hawaiian volcanism. These landslides cause huge sections of the volcano’s side to slide into the ocean, temporarily reducing its height and altering its structure. For example, the 1996 collapse that formed Pele’s Pit lowered the summit surface in that area by about 985 feet (300 meters).
The rate of growth is ultimately governed by the stability and consistency of the magma supply from the Hawaiian hotspot. Scientists have estimated an average growth rate for similar Hawaiian volcanoes at about 0.1 foot (3 cm) per year over geologic time. However, this is a long-term average, and the short-term rate fluctuates wildly based on the frequency and volume of individual eruption events and the size of any subsequent collapses.
The Estimated Timeline to Surface
The timeline for Lōʻihi to break the water line is highly dependent on unpredictable variables, leading to a wide range of scientific estimates. The consensus for the volcano to first reach the surface spans from tens of thousands of years to 100,000 years or more. A conservative calculation suggests that at a sustained, slow growth rate, emergence could take up to 200,000 years.
These long-term predictions rely on the assumption that the volcano’s magma supply remains consistent over millennia. The most significant variable is the frequency of major collapse events, which can instantly reverse decades or centuries of growth. The volcano must rebuild the lost volume after each flank collapse before it can continue its ascent toward the surface.
The initial surfacing will likely not result in a stable, permanent island immediately. When the summit gets within a few hundred feet of the surface, the reduced water pressure will trigger more explosive, steam-driven eruptions. This explosive phase will build the final cap of the volcano until it breaches the ocean surface, marking the transition from a seamount to a subaerial shield volcano.
The Next Phase of Island Development
Once Lōʻihi emerges above sea level, the nature of its volcanic activity will begin to change drastically. The intense, steam-driven eruptions that occur just below the surface will give way to the more effusive activity typical of Kīlauea and Mauna Loa. The newly formed landmass will then enter the shield-building stage, continuing to grow in size and height through repeated lava flows.
The subsequent phase involves a gradual cooling and eventual cessation of volcanic activity as the Pacific Plate carries the island away from the Hawaiian hotspot. Following its departure, the island will begin the long process of erosion and subsidence. Rain, wind, and waves will break down the volcanic rock, leading to the formation of soil and the development of fringing reefs. This geological life cycle is consistent with the history of the other Hawaiian Islands, underscoring the immense timescale of the archipelago.