The Underwater Geology of Hawaii’s Island Chain
The Pacific Plate, one of Earth’s largest tectonic plates, continuously moves northwest at a pace of several centimeters per year. This ongoing movement over a volcanic “hot spot” has led to the sequential formation of islands in an assembly-line fashion, creating the breathtaking Hawaiian archipelago.
Located near the central region of the Pacific Plate, the Hawaiian Islands consist of eight major islands and 124 smaller islets, stretching approximately 1,500 miles toward Japan and the Aleutian Islands of Alaska. The total landmass of this chain covers roughly 6,459 square miles. The largest island, commonly referred to as the Big Island, continues to expand due to volcanic activity. The other major islands, arranged from west to east, are Ni’ihau, Kaua’i, Oahu, Molokai, Lanai, Kahoolawe, and Maui.Formation and Growth of the Hawaiian Islands
Hawaii’s youngest island, aptly named Hawaii (the Big Island), began forming over a million years ago when volcanic eruptions built up layers of lava, eventually rising above the ocean’s surface. This island owes its existence to five major volcanoes that erupted at different times, overlapping lava flows to create a single landmass.
The Kohala Mountains were the first to emerge, positioned directly over the hot spot. As the Pacific Plate drifted, new volcanoes formed: Mauna Kea, Hualalai, Mauna Loa, and Kilauea. Even today, this process continues. Off the southeastern coast of the Big Island, an undersea volcano known as Lo’ihi is actively erupting. In approximately 50,000 years, Lo’ihi may rise above the ocean and either form a new island or become the sixth peak of the Big Island.The Powerhouses of the Big Island
Mauna Loa, the largest volcano on the Big Island, comprises approximately 51% of its total landmass. Unlike traditional towering peaks, Mauna Loa’s shield shape makes it appear less mountainous to the untrained eye. All of Hawaii’s volcanoes are classified as shield volcanoes, which are formed by slow-moving lava flows that build up over millions of years.
Adjacent to Mauna Loa, Kilauea is renowned as the world’s most active volcano and is considered the sacred home of Pele, the Hawaiian goddess of fire. Initially thought to be a vent of Mauna Loa, Kilauea has since been identified as an independent volcano with its own magma chamber.
Another significant geological feature of the Big Island is Mauna Kea. Covering approximately 25% of the island, this volcano is famous for its snow-capped summit in winter. In fact, Mauna Kea is the tallest mountain on Earth when measured from its base on the ocean floor, rising to an astounding 33,500 feet. This makes it even taller than Mount Everest when measured from base to peak.
Hualalai, located on the island’s west side near Kailua-Kona, and Kohala, the oldest of the island’s volcanoes, add to the geological diversity. Kohala’s rugged terrain and steep sea cliffs are the result of a massive landslide that occurred around 200,000 years ago.The Future of Hawaii’s Islands
Although the Big Island is still growing due to active volcanic eruptions, its fate will eventually mirror that of its predecessors. The Hawaiian hot spot does not move, but the Pacific Plate carries the islands northwestward. Over time, erosion and subsidence will cause the Big Island to shrink, fragmenting into smaller islands, much like what happened to Maui Nui.
Maui Nui, the former massive landmass that included Maui, Lanai, Molokai, and Kahoolawe, has since submerged, leaving behind the four distinct islands we see today. Haleakala, the dominant volcano of Maui, stands at 10,023 feet and is considered the largest dormant volcano in the world. Though it has not erupted since the late 1700s, geologists consider it dormant rather than extinct.
The Big Island of Hawaii is currently the largest island in the chain, but its future is written in geological history. As it continues its slow migration away from the hot spot, it will inevitably erode, break apart, and submerge, just as the islands before it have done. However, for the foreseeable future, volcanic activity ensures that the Big Island will remain just that—big.
The Pacific Plate, one of Earth’s largest tectonic plates, continuously moves northwest at a pace of several centimeters per year. This ongoing movement over a volcanic “hot spot” has led to the sequential formation of islands in an assembly-line fashion, creating the breathtaking Hawaiian archipelago.
Located near the central region of the Pacific Plate, the Hawaiian Islands consist of eight major islands and 124 smaller islets, stretching approximately 1,500 miles toward Japan and the Aleutian Islands of Alaska. The total landmass of this chain covers roughly 6,459 square miles. The largest island, commonly referred to as the Big Island, continues to expand due to volcanic activity. The other major islands, arranged from west to east, are Ni’ihau, Kaua’i, Oahu, Molokai, Lanai, Kahoolawe, and Maui.Formation and Growth of the Hawaiian Islands
Hawaii’s youngest island, aptly named Hawaii (the Big Island), began forming over a million years ago when volcanic eruptions built up layers of lava, eventually rising above the ocean’s surface. This island owes its existence to five major volcanoes that erupted at different times, overlapping lava flows to create a single landmass.
The Kohala Mountains were the first to emerge, positioned directly over the hot spot. As the Pacific Plate drifted, new volcanoes formed: Mauna Kea, Hualalai, Mauna Loa, and Kilauea. Even today, this process continues. Off the southeastern coast of the Big Island, an undersea volcano known as Lo’ihi is actively erupting. In approximately 50,000 years, Lo’ihi may rise above the ocean and either form a new island or become the sixth peak of the Big Island.The Powerhouses of the Big Island
Mauna Loa, the largest volcano on the Big Island, comprises approximately 51% of its total landmass. Unlike traditional towering peaks, Mauna Loa’s shield shape makes it appear less mountainous to the untrained eye. All of Hawaii’s volcanoes are classified as shield volcanoes, which are formed by slow-moving lava flows that build up over millions of years.
Adjacent to Mauna Loa, Kilauea is renowned as the world’s most active volcano and is considered the sacred home of Pele, the Hawaiian goddess of fire. Initially thought to be a vent of Mauna Loa, Kilauea has since been identified as an independent volcano with its own magma chamber.
Another significant geological feature of the Big Island is Mauna Kea. Covering approximately 25% of the island, this volcano is famous for its snow-capped summit in winter. In fact, Mauna Kea is the tallest mountain on Earth when measured from its base on the ocean floor, rising to an astounding 33,500 feet. This makes it even taller than Mount Everest when measured from base to peak.
Hualalai, located on the island’s west side near Kailua-Kona, and Kohala, the oldest of the island’s volcanoes, add to the geological diversity. Kohala’s rugged terrain and steep sea cliffs are the result of a massive landslide that occurred around 200,000 years ago.The Future of Hawaii’s Islands
Although the Big Island is still growing due to active volcanic eruptions, its fate will eventually mirror that of its predecessors. The Hawaiian hot spot does not move, but the Pacific Plate carries the islands northwestward. Over time, erosion and subsidence will cause the Big Island to shrink, fragmenting into smaller islands, much like what happened to Maui Nui.
Maui Nui, the former massive landmass that included Maui, Lanai, Molokai, and Kahoolawe, has since submerged, leaving behind the four distinct islands we see today. Haleakala, the dominant volcano of Maui, stands at 10,023 feet and is considered the largest dormant volcano in the world. Though it has not erupted since the late 1700s, geologists consider it dormant rather than extinct.
The Big Island of Hawaii is currently the largest island in the chain, but its future is written in geological history. As it continues its slow migration away from the hot spot, it will inevitably erode, break apart, and submerge, just as the islands before it have done. However, for the foreseeable future, volcanic activity ensures that the Big Island will remain just that—big.
