Mauna Loa, meaning Long mountain in English, is the largest subaerial volcano in both mass and volume. It is one of the five volcanoes that form the Island of Hawaii in the Pacific ocean. Historically, Mauna Loa has been considered the largest volcano on the Earth. The volume of Mauna Loa is estimated at approx 18,000 cubic miles. It is an active shield volcano with its peak at the height of 120 feet which is lower than its neighbor Mauna Kea. The lava of Mauna Loa is tended to be non-explosive, silica-poor and very fluid. Age of Mauna Loa is about 400,000 years ago which means it may have emerged above sea level at that time and it has probably been erupting for at least 700,000 years. The oldest-known dated rocks of Mauna Loa are not older than 200,000 years. Hawaii hotspot, the volcano's magma comes from there, has been responsible for the creation of Hawaii islands. Mauna Loa will become extinct Within 500,000 to one million years from now because the slow drift of Pacific plate will carry it away from the hotspot. March 24 to April 15, 1984, was the time period of the most recent eruption of Mauna Loa. However, there are no recent eruptions but villages got destroyed by the eruptions in 1926 and 1950.

The presence of Mauna Loa very much affects the local climate as trade winds blow from east to west across the Hawaiian islands. The eastern side of the volcano receives the heavy rain at low elevations. However, the city of Hilo is the wettest in the United States. Extensive forestation was supported by the rainfall. The skies are often clear and the amount of precipitation decreases at higher elevations.The precipitation occurs in the form of snow due to very low temperatures. The summit of Mauna Loa is described as a periglacial region. Mauna Loa has a tropical climate with highest recorded temperature was 29 degrees celsius and lowest was -8 degrees celsius on February 18, 2003, and February 20, 1962, respectively.

Global Atmosphere Watch made Mauna Loa as an important location for atmospheric monitoring and other scientific observations. THe Mauna Loa Solar Observatory(MLSO) has been prominent in the observations having located at 11,155 feet on the northern slope of the mountain. The NOAA Mauna Loa Observatory (MLO) is also nearby. The MLO monitors the global atmosphere as it is located well above local human-generated influences.Established in October 2006 by the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), The Yuan-Tseh Lee Array for Microwave Background Anisotropy (AMiBA), is located at an elevation of 11,155 feet, examines cosmic microwave background radiation.