(Volcano Watch is a weekly article written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.)

Frank Perret’s photos from early July 1911 showing the island in the lake at the bottom of a smaller Halema`uma`u Crater. The view is looking southwest and the ledge up near the west rim was known as the January 1910 bench, a remnant of an earlier lava level in the crater. Photo courtesy of USGS/HVO.

HVO’s first volcanic activity update, written by Frank Perret, the most famous American volcanologist of his time, appeared in the Pacific Commercial Advertiser (now the Honolulu Star-Advertiser) on August 15, 1911. The article described the state of the lava lake in Halema`uma`u Crater during the previous six weeks (since his arrival on July 2) and the construction of an apparatus used to measure the temperature of molten lava (described in Volcano Watch articles last month).

In July 1911, Perret wrote “The lake of lava–about 150 metres [500 ft] greatest diameter–was fairly active, with several fountains coming up at intervals of about 12 seconds. An island consisting of two unequal parts joined by a low isthmus, floated just east of the center of the crater lake. Its most remarkable feature was an arched opening under the isthmus leading to a cavity under the island, into which the surface lava of the lake was pouring in cascades from either side. The main circulation of lava in the lake was from under the southwest bank over the surface to the north and east. Estimated lava to be about 85 metres below rest-house [280 ft below the crater rim] and to be rising.”

Fast-forward to July 2011. Today, there’s another lava lake in Halema`uma`u, which, by comparison, is estimated to be about 120-130 m (400-425 ft) in diameter and 165-175 m (540-575 ft) below the rim of Halema`uma`u Crater—twice as deep as a century ago. There is no “island,” and the main circulation is currently from southeast to northwest.

Halema`uma`u Crater is quite a bit larger today than it was in 1911, thanks to the explosive eruptions of May 1924. The crater diameter is now about 1,000 m (3,300 ft) compared to less than 380 m (1,250 ft) in 1911.

Frank Perret went on to describe some of the lava lake phenomena he witnessed in 1911. “At interval[s] the level inside [the grotto beneath the island] would rise to the level of the lake and the downflow ceased, only to be resumed again later on when a fountain could be seen welling up inside the cavity. After this the level would drop and the cascade again would be formed.…”

HVO scientists witness remarkably similar behavior in the 2011 lava lake, when the spattering sink (fountaining downflow) on the northwest lake edge disappears as the lava level rises, only to reappear as the lake drops to its former level.

Buried at the end of his first report, Perret inventories the equipment that he installed and routinely used to document crater conditions. He writes, “The seismoscope is set up for visual observations and shows the ground to be continually in movement. The coming up of every fountain in the lake is clearly shown by movement of the indicator.”

The seismoscope, invented by Perret, was a way to measure changes in continuous seismic vibrations, and this was the first correlation between magma movement and tremor at Kilauea Volcano. In 2011 we also measure dramatic changes in seismic tremor associated with variations in fountaining and spattering. Increases in these types of surface activity are commonly linked to increases in seismic tremor.

Perret’s final paragraph contained a tantalizing observation: “An interesting fact is that the seismoscope shows strong tiltings in a north-south direction, that is, tangential to the crater.…”

This was the first documentation of ground tilt changes possibly related to Halema`uma`u crater activity, although the direction we see now is radial to the crater, like spokes on a wheel–at right angles to what Perret noticed.

Perret issued five more volcanic activity reports with photographs at weekly intervals, based on his observations from the Technology Station building on the east rim of Halema`uma`u Crater. Today, HVO issues daily eruption updates on our Web site hvo.wr.usgs.gov, and weekly updates are printed in local newspapers.

Next week’s Volcano Watch column will explore more of what Perret witnessed while beginning the work of the Hawaiian Volcano Observatory 100 years ago this month.