Mauna Loa is the biggest volcano on the Earth. It is one of the five volcanoes that form the Island of Hawaii in the USA. Mauna Loa has erupted 33 times between 1843 and 1984. It is a massive volcano constructed by countless lava-flows. When measured from the base to the top, the pile of lavas measures more than 17,000 metres (56,000 feet). When measured from the sea floor, Mauna Loa’s height is still more than 9,000 metres. Mauna Loa has been monitored intensively by the Hawaiian Volcano Observatory since 1912. Observations of the atmosphere are undertaken at the Mauna Loa Observatory, and of the Sun at the Mauna Loa Solar Observatory, both located near the summit of the mountain.