“Volcano Watch” is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates. Today’s article is by Hawaiian Volcano Observatory geologist Drew Downs.
Kīlauea has drawn huge crowds since December 2024 to witness the episodic lava fountaining in Halemaʻumaʻu Crater at the volcano’s summit, with many visitors hiking trails and visiting overlooks to watch the ongoing eruption.
However, there are many other trails across the unique, lava-strewn landscape of Kīlauea that can be hiked during pauses between lava fountaining episodes, including the Footprints Trail.
The start of this trail can be found just off Highway 11 about 10 miles to the southwest of the main entrance to Hawaiʻi Volcanoes National Park near Kīlauea summit. A short hike leads to a covered pavilion with signage that describes the origin of the trail name, where footprints of Native Hawaiians who walked in wet ash that fell during an explosive eruption in 1790 can still be found.
Many visitors hike out to look at the footprints before turning around.
However, another mile along the trail brings hikers to the unvegetated heart of Kaʻū Desert and low slope that leads to the top of the Maunaiki shield.
This is one of the more prominent, high-standing features along Kīlauea’s Southwest Rift Zone, providing views for miles in every direction, with other trails leading farther into Kaʻū Desert for those who packed plenty of water and sunscreen.
The Maunaiki shield itself is a relatively recent addition to the landscape. This broad high point with great views formed during 8 months from December 1919 to August 1920.
At the time of the Maunaiki eruption, the Hawaiian Volcano Observatory was still relatively new, having started operations in 1912. Thomas Jaggar and Ruy Finch were the two observatory geologists tasked with monitoring volcanic activity.
Before the eruption started, a persistent and long-lived lava lake occupied Halemaʻumaʻu. On Nov. 28, 1919, this lava lake drained by more than 600 feet during 4 hours. It took 17 days for Halemaʻumaʻu to refill back up to its crater rim.
Less than a month later, from Dec. 15-23, 1919, a magmatic dike intruded from the summit about 6 miles into the Southwest Rift Zone. Volcanic gases were seen coming from ground cracks and observers could occasionally see molten lava deep within.
A small lava fountain started to erupt on Christmas Eve 1919, feeding pāhoehoe flows in the area where the Maunaiki shield now sits. At the same time, the level of the Halemaʻumaʻu lava lake started to fall, indicating a hydraulic connection between the summit and the rift zone.
A large volume of ‘a‘ā lava began flowing downhill Dec. 30, 1919, to the southwest from the lava fountain vent. This lava flow lasted until Jan. 17, 1920, and made it 7 miles from the vent.
Most of the height of the Maunaiki shield climbed when hiking the present day trail was built from Jan. 18 through April 16 in 1920. During that time, a lava pond formed and its pāhoehoe overflows slowly built up the shield structure that came to be called Maunaiki.
Not far from the hiking trail on the flank of the shield there is a noticeable ‘a‘ā flow covering the pāhoehoe slopes. It is thought that this part of the shield accumulated lava at shallow depths, causing the surface to bulge, then it broke open and created this little flow.
The Maunaiki shield stopped growing by mid-April 1920, and lava tubes had formed to more efficiently transport lava downhill. Lava flowed until Aug. 3, 1920, at which point the eruption came to an end.
Next time you are waiting for a lava fountain to start, consider packing some water, snacks and sunscreen so you can go check out the views from the top of Maunaiki and the volcanic activity of the recent past that sculpted the landscape of Kīlauea’s Southwest Rift Zone in Hawaiʻi Volcanoes National Park.
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VOLCANO ACTIVITY UPDATES
KĪLAUEA volcano
VOLCANO ALERT LEVEL: Watch
Kīlauea has erupting episodically since Dec. 23, 2024, within the summit caldera. Episode 54 of lava fountaining was Aug. 25 for 9 hours. Episode 55 precursory lava flows began Sept. 7, with 50 lava flows since then. No unusual activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone.
WHAT’S NEXT: Summit region inflation has been very irregular following episode 54, with little change during the past several days. The forecast for the start of Episode 55 is Sept. 10-11, but this could be pushed back further with continued precursory lava flows and little ground deformation.
MAUNA LOA volcano
VOLCANO ALERT LEVEL: Normal.
Mauna Loa is not erupting. Read the most recent monthly Mauna Loa activity update online.
Hawaiian Volcano Observatory continues to closely monitor Kīlauea and Mauna Loa.
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EARTHQUAKE ACTIVITY UPDATE
Three earthquakes were reported felt during the past week in the Hawaiian Islands:
- MAGNITUDE-2.8 earthquake at 9:06 p.m. Sept. 7 located 2 miles north-northwest of Honomu at a depth of 13 miles.
- MAGNITUDE-3.5 earthquake at 2:20 a.m. Sept. 4 located 3 miles south of Pāhala at a depth of 7 miles.
- MAGNITUDE-3.4 earthquake at 12:39 p.m. Sept. 3 located 11 miles southeast of Pāhala at a depth of 19 miles.
Visit the Hawaiian Volcano Observatory website for past “Volcano Watch” articles, Kīlauea and Mauna Loa updates, volcano photos, maps, recent earthquake information and more. Email questions to askHVO@usgs.gov.
