Maui, often called “The Valley Isle,” is a single landmass created by two distinct volcanic structures. The factual answer to how many volcanoes are on Maui is two, which together form the majority of the island’s terrain. These colossal shield volcanoes grew over millions of years from the seafloor, eventually breaching the ocean surface. The difference in their age and recent activity defines Maui’s contrasting landscapes, from gentle slopes to rugged mountains.
The Island’s Dual Formation
The island of Maui is a classic example of two shield volcanoes growing so close together that their lava flows coalesced. These two primary structures are the East Maui Volcano, commonly known as Haleakalā, and the West Maui Volcano, called Mauna Kahalawai.
This geological merging created a low-lying, flat region between the two volcanic mountains. This narrow stretch of land is known as the Central Valley or the isthmus of Maui, connecting the two larger land masses. The isthmus was filled in by younger lava flows and sediments washing down from the Haleakalā structure. This process resulted in the hourglass shape of Maui, with the two volcanoes forming the eastern and western lobes of the island.
Haleakalā: Maui’s Dormant Giant
The East Maui Volcano, Haleakalā, is the younger and larger of the two structures, forming the entire eastern portion of the island. This shield volcano rises to a peak of 10,023 feet (3,055 meters) above sea level, though its base extends nearly 19,000 feet below the ocean surface. Haleakalā is not classified as extinct, but is considered dormant by the U.S. Geological Survey.
This dormant classification is due to its history of relatively recent eruptions, indicating it remains capable of becoming active again. The most recent lava flows occurred along Haleakalā’s southwest rift zone, dated between 1480 and 1600 CE. Because the volcano has erupted at least ten times in the last 1,000 years, it is actively monitored for signs of seismic unrest or ground deformation.
The West Maui Mountains (Mauna Kahalawai)
The West Maui Mountains, or Mauna Kahalawai, form the smaller and older western lobe of the island. This structure began forming approximately 1.7 million years ago, making it older than its eastern neighbor. The highest point of this range is Pu’u Kukui, which reaches an elevation of 5,788 feet.
Mauna Kahalawai is classified as an extinct volcano because its final eruptions occurred around 320,000 years ago. The long period since its last activity has allowed weather to reshape the mountain dramatically. Extremely heavy rainfall, which can exceed 389 inches annually at the summit, has deeply dissected the volcano. This erosion has carved the original gentle shield into the steep ridges and deep valleys, such as the famous ʻĪao Valley, that characterize the West Maui Mountains today.