Frequent and long-lasting eruptions and recurrent strong earthquakes in Hawai‘i create a unique combination of natural hazards for people across the Hawaiian Islands. This is especially true for residents on the Island of Hawai‘i, which consists of five volcanoes, four of which are classified as active—Kīlauea, Mauna Loa, Hualālai, and Mauna Kea. Two other active volcanoes in Hawaii include Lō‘ihi, a submarine volcano south of the Island of Hawai‘i, and Haleakalā on the Island of Maui. Since 1868, more than 30 magnitude-6.0 or greater earthquakes have struck the Hawaiian Islands, causing damage and impacting residents across the state. Most of these large earthquakes were located on or near the Island of Hawai‘i, but others have occurred near the islands of Maui and Moloka‘i.
HVO scientists work to improve understanding of volcanic and seismic hazards in Hawaii through field studies, research, and continuous monitoring.
Lava flows typically erupt from a volcano's summit or along rift zones on its flanks. Lava flows travel downslope toward the ocean, burying everything along the way. Lava entering the ocean may build new land known as lava deltas, which are unstable and prone to sudden collapse. A collapsing lava delta can trigger explosive activity that hurls hot rocks hundreds of meters (yards) inland and/or seaward.
On the Island of Hawai‘i, about 40 percent of Mauna Loa has been covered by lava erupted in the past 1,000 years. More than 90 percent of Kīlauea's surface has been covered by lava in the same time frame.
USGS scientists have identified lava flow hazard zones using the record of past lava flows combined with detailed topographic maps. HVO scientists forecast the path of a new lava flow based on these earlier flows and highly detailed three-dimensional maps (digital elevation models) of the ground.
Many strong explosive eruptions have occurred at Kīlauea Volcano during the past 2,500 years. According to current understanding of eruption history, the volcano has alternated between centuries-long periods of dominantly effusive (lava flow) and dominantly explosive eruptions. A change in the current effusive period at Kīlauea will present significant hazards from future explosive eruptions, including fast-moving pyroclastic flows and surges across the volcano's summit area, as well as tephra falling over broad areas of the Island of Hawai‘i.
Large amounts of volcanic gas—primarily water vapor (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2)—are continuously released during the ongoing eruptions of Kīlauea Volcano. As SO2 is released from the summit and East Rift Zone eruptive vents, it reacts in the atmosphere with oxygen, sunlight, moisture, and other gases and particles, and within hours to days, converts to fine particles. The particles scatter sunlight and cause the visible haze that is observed downwind of Kīlauea, known as vog (volcanic smog). Vog creates the potential for airborne health hazards to residents and visitors, damages agricultural crops and other plants, and affects livestock operations.
Hawai‘i has a history of many strong, destructive earthquakes—including a magnitude-6.7 in 2006 and a magnitude-7.7 in 1975. Strong earthquakes endanger people and property by shaking structures and by causing ground cracks, ground settling, landslides, and tsunamis. Such earthquakes have destroyed buildings, collapsed water tanks, damaged roads and bridges, and disrupted water, sewer, and utility lines.