Volcano Watch: East Rift Zone of Kīlauea was busy place in the 1960s

by US Geological Survey Hawaiian Volcano Observatory scientists and affiliates

The recent eruption at Nāpau Crater was the first on Kīlauea’s middle East Rift Zone in six years.

We often remember the Pu‘u‘ō‘ō and Maunaulu eruptions when thinking about the middle East Rift Zone, but many lesser-known eruptions occurred on the rift zone in the past 200 years, including 11 during the 1960s.

While there were several summit eruptions at Kīlauea during the same decade, including one that lasted more than 8 months, eruptions along the East Rift Zone — mainly in the upper and middle portions — were much more frequent.

Before the 1955 lower East Rift Zone eruption, the last eruption on the rift zone took place in 1923 near Makaopuhi Crater.

Following the 1960 Kapoho eruption and three quick summit eruptions in the first half of 1961, a new short-lived East Rift Zone eruption began in late September that year.

During the course of 2 days, 13 small flows erupted from vents that spread over 13 miles of the rift zone, from Nāpau Crater to within 2.5 miles of the area where Leilani Estates was later built.

The largest lava flows from this eruption were located at the lower end of the fissure system closest to Pāhoa and fed by lava fountains 300 to 400 feet tall.

Two additional 2-day eruptions happened in December 1962 and August 1963, just uprift of Nāpau Crater.

Both were very small and their lava flows only covered a combined total of about 40 acres, a quarter of the size of the 1961 flows.

Less than 2 months later, a new eruption began along an 8-mile stretch of the rift zone starting at Nāpau Crater and migrating east, downrift to Kalalua Crater.

The single day eruption in October 1963 was much larger than the three previous eruptions, though it covered only 800 acres.

Fissures opened on the rim and floor of Nāpau Crater, sending lava cascades down the crater wall. Flows covered about 75% of the crater floor.

Short-lived eruptions in March and December of 1965 again opened on the East Rift Zone, uprift of Nāpau Crater.

There was a nearly 2-year hiatus in eruptions at Kīlauea volcano after that until a new eruption started at the summit in late 1967, lasting 251 days.

Activity later once again shifted back to the East Rift Zone, with eruptions in August and October of 1968 in the upper and middle East Rift Zone. Associated seismicity and severe ground deformation were recorded at the summit and eruption sites.

On the first day of the August 1968 eruption, fissures opened across the floor and walls of Hi‘iaka Crater, the westernmost eruption site on the upper East Rift Zone during the 1960s.

A small lava lake drowned some of the fissures on the crater floor, where much of the ponded lava drained back. Additional fissures opened to the east during the next few days, but only produced small amounts of lava.

After a little more than a month, the October eruption was preceded by tremor and shallow earthquakes in the summit and upper East Rift Zone.

The eruption, which lasted 15 days, was the longest in this sequence of middle East Rift eruptions, spanning from Kānenuiohamo to about where Pu‘u‘ō‘ō cone is now.

The eruption shifted along a fissure system but repeatedly focused in and around Nāpau Crater, often flooding the crater floor and sending lava cascading down the crater walls.

Kīlauea put on a spectacular show as the decade came to a close, with the start of the Maunaulu eruption on May 24, 1969. A series of high fountaining events reaching 1,770 feet were some of the highest recorded at Kīlauea.

Lava flows from this eruption extended south to the ocean and covered large portions of the old Chain of Craters Road.

It was, at the time, the largest and longest East Rift Zone eruption in more than 2,000 years before it ended in 1974.

As we continue into this new and dynamic era at Kīlauea, it is relevant to look at the volcano’s past behaviors for clues about what the future might hold.

The East Rift Zone is known to be quite active, but only time will tell where the volcano erupts next.

Volcano Activity Updates

Kīlauea is not erupting. Its U.S. Geological Survey Volcano Alert level is at Advisory.

During the past week, earthquake rates beneath Kīlauea summit and upper and middle East Rift Zone nearly doubled. About 50 earthquakes were located beneath the summit and about 190 in the upper and middle East Rift Zone.

Ground deformation rates remain low following the Sept. 15-20 middle East Rift Zone eruption, but continue to show that magma is moving at a low rate from the summit to the middle East Rift Zone.

Future intrusive episodes and eruptions could occur with continued magma supply.

The most recent measurement of sulfur dioxide emission rate at the summit was 60 tonnes per day Sept. 17. Sulfur dioxide emissions were not detected downwind of the eruption site Sept. 23.

Maunaloa is not erupting. Its U.S. Geological Survey Volcano Alert Level is at Normal.

No earthquakes were reported felt in the Hawaiian Islands during the past week.

The Hawaiian Volcano Observatory continues to closely monitor Kīlauea and Maunaloa.

Visit the observatory website for past “Volcano Watch” articles, Kīlauea and Maunaloa updates, volcano photos, maps, recent earthquake information and more. Email questions to askHVO@usgs.gov.