Hawaii is full of fascinating mountain peaks, though there is perhaps none more intriguing than Hawaii Island’s Mauna Loa, one of five shield volcanoes that forms the Big Island. The massive volcano is one of the most active in the world, and makes up more than half of the Big Island’s surface area.
Mauna Loa is the largest sub-aerial volcano in both mass and volume in the world, and is the second largest overall volcano on earth, just behind Tamu Massif.
The volcano covers a land area of approximately 2,035 square miles, and when measured from the base on the ocean floor to the summit, is just over 30,000 feet tall.
Its peak is approximately 120 feet lower than that of its neighbor, Mauna Kea, though its volume is estimated to be 18,000 cubic miles.
In this photograph, you can see Mauna Loa as seen from Mauna Kea.
The active shield volcano has most likely been erupting for at least 700,000 years, and emerged from above sea level an estimated 400,000 years ago, though the oldest known dated rocks are not older than 200,000 years.
Lava eruptions from Mauna Loa’s summit are poor in silica, very fluid, and most often, non-explosive.
The most recent eruption occurred from March 24 to April 15, 1984. While no recent eruptions have caused fatalities, lava flows in 1926 and 1950 destroyed villages – the city of Hilo is partially built upon lava flows from the late 19th century.
The volcano’s 1942 eruption occurred just four months after the Japanese attack on Pearl Harbor, and presented a rather unique problem.
The eruption, which occurred during a forced nighttime blackout on the island, forced the government to issue a gag order on the local press in an attempt to prevent news of the eruption in fear that the Japanese would use the opportunity to launch a bombing spree on the island.
Mauna Loa is historically less active than its neighbor, Kilauea, though the volcano has historically produced greater volumes of lava over a shorter period of time.
Almost 90 percent of Mauna Loa’s surface is covered by lava flows less than 4,000 years old, 50 percent of the surface is covered by lava no older than 1,500 years, and 25 percent is covered by lava flows younger than 750 years.
Fun fact: Lava fields on Mauna Loa have been frequently used as a training ground for astronauts headed to the moon.
Mauna Loa has been quiet for more than 30 years, though it appears as though that might be changing soon.
The volcano was raised to a yellow alert status after continued deformation of the surface and shallow earthquakes at the summit – signs that came before eruptions in 1975 and 1984. This, however, does not mean an eruption is imminent.