esting place by flying through the air ballistically. After a little practice, recognizing the ballistics became a simple matter. Some of the rocks are even coarse-grained gabbro, which cooled and crystallized underground before being blasted out.
What we found surprised, even shocked, us. Rather than seeing few, if any, large rocks so far from the caldera, we found lots. And some were very large.
At a distance of 10 km (6 miles) from the summit, we found one rock (a gabbro) weighing 1292 g (2 lbs 13 oz.). At 7.9 km (4.7 miles) from the summit, we found another weighing 1998 g (4 lbs 5 oz.). Many others weigh 100 g (3.5 oz.) or more.
When we compared our findings with theoretical models of how far such large rocks could have been thrown from a volcanic vent, we found that we were observing the impossible. The models simply say no dice, it can't be done. Even if we assume that the source for the rocks was on the east rift zone, say near Pauahi Crater or Mauna Ulu, the distance of more than 5.25 km (3.2 miles) is still too great for the models to accept. But, models or no models, the rocks traveled through the air to get where we found them-and that has to be explained.
We think we are on to something. Kilauea has likely had explosions that were either more powerful, or of a different type, than existing theoretical models can explain.
Before you toss out theory, all steps in the observation and interpretation process must be checked and double checked. We are doing that now. Explosions of such unusual power or type are significant; we can leave no stone unturned (pun intended) in trying to determine their nature and cause.
Eruptive activity of Kilauea Volcano continued unabated during the past week, following a brief pause two weeks ago. Lava is erupting from Pu`u `O`o and flowing through the old tube system for 1.5 km (0.9 mi) to the southeast. Breakouts from the old tube system at the 2,300-ft elevation feed two diverging flows. One flow is to the southwest and extends down to the 1900-ft elevation. The second flow is to the southeast and extends 3.6 km (2.2 mi) down to the 1700-ft elevation.
Residents of Pahala felt an earthquake at 7:06 p.m. on September 3. The magnitude-3.4 earthquake was located 4 km (2.4 mi) south of Pahala at a depth of 11 km (6.6 mi).
The URL of this page is http://hvo.wr.usgs.gov/volcanowatch/archive/2000/00_09_07.html
Updated: September 11, 2000