Volcano Watch: The East Rift Zone of Kilauea was a busy place in the 1960s

The recent eruption at Napau Crater was the first on Kilauea’s middle East Rift Zone (ERZ) in six years. We often remember the Pu‘u‘o‘o 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 Kilauea during the 60s, including one that lasted more than 8 months, eruptions along the ERZ (mainly in the upper and middle portions) were much more frequent. Before the 1955 lower ERZ eruption, the last eruption on the ERZ had taken place near Makaopuhi Crater in 1923.

Following the 1960 Kapoho eruption and three quick summit eruptions in the first half of 1961, a new short-lived ERZ eruption began in late September of that year. Over the course of two days, 13 small flows erupted from vents that were spread over 21 km (13 mi) of the rift zone from Napau crater to within 4 km (2.5 mi) of the area where Leilani Estates Subdivision was later built. The largest lava flows from this eruption were located at the lower end of the fissure system closest to Pahoa and fed by lava fountains 90 to 120 meters (300–400 ft) tall.

Two additional 2-day-long eruptions took place in December 1962 and August 1963 just uprift of Napau Crater. Both eruptions were very small and their lava flows only covered a combined total of 0.16 square km or about 40 acres of land, a quarter of the size of the 1961 flows.

Less than two months later, a new eruption began along a 13 km (8 mi) stretch of the rift zone starting at Napau 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 3.24 square km (800 acres). Fissures opened on the rim and floor of Napau Crater, sending lava cascades down the crater wall and flows covered about 75 percent of the crater floor.

In 1965, short-lived eruptions in March and December again opened on the ERZ — uprift of Napau Crater. After this time, there was a nearly two-year hiatus in eruptions at Kilauea volcano until a new eruption started at the summit in late 1967, lasting 251 days.

After that, activity once again shifted back to the ERZ with eruptions in the upper and middle ERZ in August and October of 1968. 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 ERZ 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 over the next few days, but only produced small amounts of lava.

After a little over a month, the October eruption was preceded by tremor and shallow earthquakes in the summit and upper ERZ. The eruption, which lasted 15 days, was the longest in this sequence of middle ERZ eruptions, and spanned from Kanenuiohamo to about where Pu‘u‘o‘o cone is now.

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

As the decade came to an end, Kilauea put on a spectacular show with the start of the Maunaulu eruption on May 24, 1969. A series of high fountaining events reaching 540 m (1770 ft), were some of the highest recorded at Kilauea. Lava flows from this eruption extended south to the ocean, covered large portions of the old Chain of Craters Road, and was (at the time) the largest and longest ERZ eruption in over 2000 years before it came to an end in 1974.

As we continue into this new and dynamic era at Kilauea, it is relevant to look at the past behaviors of the volcano for clues into what the future may hold. The ERZ is known to be quite active, but only time will tell where the volcano erupts next.

Volcano activity updates

Kilauea is not erupting. Its USGS Volcano Alert level is ADVISORY.

Over the past week, earthquake rates beneath Kilauea summit and upper-to-middle East Rift Zone have nearly doubled. About 50 earthquakes were located beneath the summit, and about 190 were located in the upper-to-middle East Rift Zone.

Ground deformation rates remain low following the September 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 (SO2) emission rate at the summit was 60 tonnes per day on September 17, 2024, and SO2 emissions were not detected at downwind of the eruption site on Monday, September 23.

Mauna Loa is not erupting. Its USGS Volcano Alert Level is at NORMAL.

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

HVO continues to closely monitor Kilauea and Mauna Loa.

Please visit HVO’s website for past Volcano Watch articles, Kilauea and Mauna Loa updates, volcano photos, maps, recent earthquake information, and more. Email questions to askHVO@usgs.gov.

Volcano Watch is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates.