Images

Thomas Jaggar and his wife, Isabel, hiking on Mauna Loa during the September 1919 Southwest Rift Zone eruption.

The summit of Mauna Loa (left) rises above the vog layer on the leeward side of the Island of Hawai‘i in November 2012. The flank of Hualālai is visible at right.

The Hawaiian Volcano Observatory and Jaggar Museum, shown in this photo, sit atop the summit of Kīlauea Volcano. The snow-capped summit of Mauna Loa, nearly 10,000 feet higher than Kīlauea, looms in the background.

The Hawaiian Volcano Observatory and Jaggar Museum, shown in this photo, sit atop the summit of Kīlauea Volcano. The snow-capped summit of Mauna Loa, nearly 10,000 feet higher than Kīlauea, looms in the background.

Erupting vents on Mauna Loa's northeast rift zone near Pu‘u ‘Ula‘ula (Red Hill) on March 25, 1984, sent massive ‘A‘ā lava flows down the rift toward Kulani.

View looking downslope at the various cones that dot Mauna Loa's Northeast Rift Zone. The edge of North Pit, on the north side of Moku‘āweoweo, is in the foreground.

Aerial view of Mauna Loa's upper northeast rift zone near the area where it intersects Moku‘āweoweo, the summit caldera. Pāhoehoe flows visible in the foreground were erupted in 1942. Distant steep cliffs (right background) are the west wall of the summit caldera.

View from just below the summit of Mauna Loa looking back down the Southwest Rift. The Sulfur Cone is the white area just above center frame. Pu‘u o Keokeo is the barely visible bump just above Sulfur Cone at the crest of the Southwest Rift.

View from above Mauna Loa's upper Northeast Rift Zone looking across an unnamed cone toward Mauna Kea.

A close-up view of the 1984 fissure that cut through the southwest side of Mauna Loa's 1940 vent cone. The crack on the right side of the cone is the 1984 fissure.

View looking up Mauna Loa's spectacular Southwest Rift Zone. Pu‘u o Keokeo fills the lower half of the photo. The black lava beyond is mostly from 1916 and 1926. The summit of Mauna Loa is in the background.

The high point of Mauna Loa, in the background at an elevation of about 13,679 ft, is actually just the highest point along the rim of the steep cliffs that surround Mauna Loa's summit caldera, Moku‘āweoweo, Dark-colored lava flows of recent vintage (1984) cover the floor of Moku‘āweoweo. View is looking southwest.

This view of Mauna Loa's 1940 vent cone, looking to the southwest, shows a fissure that bisected it during the 1984 eruption (crack on the right side of the cone). Pāhoehoe flows and spatter erupted from the 1984 fissure blanket the caldera floor northwest of the cone (foreground).

This aerial view of Mauna Loa's summit shows the cinder-cone and lava flows that were erupted in 1949. The crack extending down the left side of the cone is the northeast-southwest trending 1984 fissure that bisected the southwest flank of the cone during the initial phase of the eruption. Light-brown tephra erupted from the 1949 cone thins to the west.

This view of Mauna Loa's summit is looking toward the northeast. The east flank of Mauna Kea is to the left, and North Pit, on the northeast end of Moku‘āweoweo, is straight ahead.

A view of Moku‘āweoweo, the summit caldera of Mauna Loa, as seen from South Pit (looking to the north-northwest). An eruption in 1940 created the cinder-and-spatter cone visible on the caldera floor (right center). This cone, which is about 114 m (373 feet) high, is the largest cone at Mauna Loa's summit.

An aerial view of the 1940 cinder-and-spatter cone on the floor of Mauna Loa's summit caldera as seen from the southeast. The west wall of the caldera (background) is about 170 m (560 feet) high. Most of the caldera floor around the cone is covered by lava flows erupted in 1984.

Solar-powered seismic station located near the summit of Mauna Loa Volcano, Hawai‘i.

Lava fountains up to 20 m (65 ft) high erupted from fissures on the north flank of Mauna Loa early Sunday morning, July 6, 1975. USGS photo.

On July 6, 1975, eruptive fissures opened along Mauna Loa

Lava fountains erupt from a fissure in the southwestern part of Moku`aeoweo, Mauna Loa's summit caldera, on April 11, 1940 (view looking to the south-southeast). Patches of white snow cling to the caldera walls as fluid pahoehoe lava flows spread across