Volcano Watch — A stone ice cream cone at the 1969 fissure along Chain of Craters Road

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The Chain of Craters Road took it on the chin in 1969. An eruptive fissure cut the road just west of `Alae Crater on February 22, closing the road to vehicles. Once the eruption ended, the road was opened as far as `Alo`i Crater, and many visitors hiked the trail from `Alo`i to the top of Pu`u Huluhulu to view the February lava flows in the distance. (`Alo`i was a small crater about 800 m [half a mile] beyond the current parking area at Mauna Ulu, and `Alae was a large crater another 1.5 km [1 mile] farther. Both are now filled with lava flows.)

This situation changed abruptly at 0445 on May 24. A fissure opened across `Alo`i Crater, and by 0500 extended westward across the Chain of Craters Road. As dawn approached, the fissure, erupting lava in a continuous line of low fountains, continued to split open toward the west. By 0830, the fissure cut the `Ainahou Road, the southward continuation of the Escape Road into `Ainahou Ranch, then a private inholding in the park. The fissure reached another 150 m (500 feet) west before ending.

This was the start of the Mauna Ulu eruption, which lasted until 1974. Mauna Ulu itself was built over a segment of the fissure system that extended eastward from `Alo`i.

The Chain of Craters Road was reopened as far as the current Mauna Ulu parking lot. Later, the road was reconnected to Kalapana, wisely avoiding Mauna Ulu by turning southward and following the upper part of the `Ainahou Road to Kulanaokuaiki Pali before striking off southeastward across previously unroaded ground to Kealakomo mauka.

Today pullouts on both sides of the Chain of Craters Road, where it follows the old `Ainahou Road, allow visitors to park and examine the fissure, spatter ramparts, lava trees (tree molds), and many other features created on May 24, 1969.

From the pullouts, walk 100 m (300 feet) north along the road. Then leave the road, heading northeastward toward Mauna Ulu. For 2-3 minutes, hike across the lava flow from the nearby fissure, coated by crunchy cinder produced by high lava fountains from Mauna Ulu later in 1969. Head for the highest bare ridges, which are spatter ramparts (coalesced spatter cones) formed by falling spatter during the fountaining on the morning of May 24.

The eruptive fissure lies at the south base of the ramparts; it is locally flanked by two ramparts. The wall of the fissure is oxidized red in many places, and there is clear evidence of late-stage drainback of lava into the fissure from the upslope side once fountains had died.

Most of the spatter ramparts and individual cakes of spatter (cow-dung bombs) are on the northeast (uphill) side of the fissure. We know that trade winds were blowing that morning, so spatter should have fallen on the southwest side, too. Where did it go? The answer is simple. Any spatter falling on the downhill side of the fissure was carried away by the lava flow.

One finds lava trees (tree molds) right along the fissure, though they don't look like trees. They form misshapen mounds, each of which is a former tree coated with lava. Most trees downslope from the fissure were bowled over or otherwise covered by the lava flow.

One tree, however, stands impressively above the flow some 30 m (100 feet) south of the fissure just beyond the highest rampart. This sturdy relic, resembling an ice cream cone with a generous scoop, is thickly coated with solidified lava but has a cap made of spatter ejected by the fountains. The height of the tree mold indicates how thick the foamy lava was at one time. As the level of lava dropped, the top of the mold emerged, catching and preserving spatter that was elsewhere carried off by the lava.

Enjoy this stop at the 1969 fissure. It is well worth a few minutes of your time, and bring your camera!

Volcano Activity Update

Eruptive activity at the Pu`u `O`o vent of Kīlauea Volcano continued unabated during the past week. Surface activity is mainly visible in the westernmost section of the pali flow field. Lava of the Kohola flow cascades down Paliuli and fans out onto the coastal flats. The distal end of the active flow is 1 km (.6 mi) from the ocean. Surface activity along the east-side lobe of the main Mother's Day flow has diminished but is still evident. Lava stopped entering the ocean at the Highcastle delta, and there is no ocean entry at this time.

Two earthquakes were reported felt on the island this past week. Residents of Kukuihaele, Waimea, and Pepe`ekeo were shaken at 8:06 p.m. on Saturday, August 2. The magnitude-2.7 event was located 6 km (3.6 mi) northwest of Honoka`a at a depth of 28 km (16.8 mi). At 8:56 p.m. on Sunday, August 3, residents of Captain Cook, Honaunau, South Point road, Wai`ohinu, Na`alehu, and Glenwood felt the earth move. The magnitude-3.3 earthquake was located 16 km (9.6 mi) southeast of Na`alehu at a depth of 35 km (21 mi).

Mauna Loa is not erupting. The summit region continues to inflate slowly. Seismic activity remains low, with only one earthquake located in the summit area during the last seven days.