Mauna Loa is in Hawaii -- more specifically, on the island also called Hawaii or the Big Island. Directly southeast of Mauna Loa is Kilauea, a significantly smaller but more frequently erupting volcano. Mauna Loa comprises more than half of the island's area.
Mauna Loa is the biggest volcano on earth, but it isn't the tallest -- that distinction belongs to Mauna Kea, a volcano directly north of Mauna Loa and 40 meters taller. Still, Mauna Loa is relatively tall. Measured from its undersea base, the volcano is approximately 56,000 feet tall, making it taller than Mt. Everest. Only a fraction of that is above sea level, though -- about 13,680 feet rise above the ocean. The volcano covers an area of 2,034 square miles.
Though the volcano's eruptions have only been well documented since 1843, Mauna Loa has been erupting for a time estimated to be between 700,000 and 1 million years. The oldest rocks recovered from the volcano are between 100,000 and 200,000 years old. Scientists estimate that the peak of Mauna Loa emerged from underneath the ocean about 400,000 years ago. Based on the movement of underground plates, however, the currently active volcano will go extinct within 500,000 to 1 million years from now.
Mauna Loa isn't just the planet's biggest volcano, it is also one of its most active. Since its first documented eruption in 1843, the volcano has erupted 33 times. As of 2011, its most recent eruption was in early 1984. Its eruptions yield a relatively large volume of fast-moving lava, endangering inhabitants of the island. Scientists predict that Mauna Loa will continue to erupt, and they monitor its activity closely.
