(Public domain.) Large landslides dissected Mauna Loa during its rapid growth View to east-southeast of Kealakekua Bay State Historic Park. High cliffs of Kealakekua Bay (west side Hawai‘i Island) formed as a result of a large Mauna Loa landslide (‘Ālika 2). Summit derived activity lasted for 10 centuries! The decline in summit-derived flows and increase in rift zone activity was likely related to the formation of Moku‘āweoweo Caldera due to collapse of the summit-lava flows erupted within the caldera were trapped, unable to overflow the caldera rim. Before about 700 years ago back to 200 BCE, lava was erupted primarily from the summit area onto the west, north, and east flanks of the volcano with flows reaching the sea. Since 1200 CE, roughly the past 700 years, eruptions occurred primarily from vents located on Mauna Loa's rift zones. Vent locations for these recent flows have generally alternated twice between the summit area and the rift zones, with each period lasting many centuries. By tracing the flows back to their vents and knowing their ages based on radiocarbon dating, geologists have recognized a general pattern in the frequency of lava flows spreading from the summit area and the rift zones during the past few thousand years. Hundreds of lava flows were erupted during this time, but they did not cover the volcano evenly. (Public domain.)ĭetailed geologic mapping and dating of lava flows above sea level have shown that about 90 percent of Mauna Loa's surface is covered with flows erupted within the past 4,000 years. Visit Media to see details.Īerial view by the Naval Air Service of the 1933 Mauna Loa eruption from a fissure across the rim and floor of Moku‘āweoweo Crater. Map of Mauna Loa's activity over the past ~200 years Geologists have mapped at least 33 radial vents on the north and west sectors of the volcano, which signifies lava can erupt from these sectors of the volcano in addition to the rift zones and summit area. Below that elevation are the northeast and southwest rift zones, and the southeast and north and west flanks. The summit area is that part of the volcano above the 3,660-m (12,000 ft) elevation, includes Moku‘āweoweo Caldera and the uppermost parts of the two rift zones.

When describing the location of eruptions and lava flows on Mauna Loa, scientists refer to five broad areas on the volcano. It likely emerged above sea level about 300,000 years ago, and it has grown rapidly upward since then. The volcano's earliest lava flows erupted onto the seafloor and submarine flanks of adjacent Hualālai or Mauna Kea volcanoes between about 0.6 and 1 million years ago. Scientists calculate Mauna Loa's volume to be at least 75,000 km 3 (18,000 mi 3). It has a surface area of about 5,100 km 2 (1900 mi 2) and a submarine area that is even more massive.

Mauna Loa dominates the Island of Hawai‘i, covering just over half the island. The caldera floor is about 180 m (590 ft) below the summit on the western rim (top right). Mauna Loa's large summit caldera (Moku‘āweoweo) measures 5 by 3.2 km (3 by 2 mi), including the summit collapse pits, and is elongated in a northeast-southwest orientation.

Mauno loa volcano parts