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

The recent eruption in Hawai'i Volcanoes National Park at Nāpau Crater was the first on Kīlauea’s middle East Rift Zone (ERZ) 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 '60s, including one that lasted more than eight 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 kilometers (13 miles) of the rift zone from Nāpau crater to within 4 kilometers (2.5 miles) 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 Pāhoa and fed by lava fountains 90 to 120 meters (300–400 feet) tall.

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

A fissure on the northwestern crater wall of Makauopuhi Crater on the East Rift Zone of Kīlauea sent lava cascading into the deepest portion of the crater, forming a lava lake. USGS photo taken by E. Endo on March 6, 1965, from a viewing area along the old Chain of Craters Road/USGS

Less than two months later, a new eruption began along a 13-kilometer (8 miles) 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 3.24 square kilometers (800 acres). Fissures opened on the rim and floor of Nāpau 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 Nāpau Crater. After this time, there was a nearly two-year hiatus in eruptions at Kīlauea 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 Kānenuiohamo to about where Pu‘u‘ō‘ō cone is now. The eruption shifted along the fissure system but repeatedly focused in and around Nāpau Crater, often flooding the crater floor and sending lava cascading down the crater walls.

As the decade came to an end, Kīlauea put on a spectacular show with the start of the Maunaulu eruption on May 24, 1969. A series of high fountaining events reaching 540 meters (1770 feet), were some of the highest recorded at Kīlauea. 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 Kīlauea, 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.