Volcano Watch — Devil's Throat has evolved into a shadow of its former self

Such is the case with Devil's Throat, a small, young pit crater on Kīlauea's east rift zone. This name conjures up a dark, mysterious place, foreboding, dangerous, something to be avoided by all but the adventurous. Indeed, that was once the case, but the devilish crater evolved into a mere imp during the 20th century. Here's what happened.

Devil's Throat lacks a Hawaiian name and so is almost certainly young, probably forming in the late 1800s. It was first mentioned in a book by William Brigham published in 1909. Three years later, Thomas Jaggar described the "Throat" as 15 m by 10.5 m (50 ft by 35 ft) across, the longer axis parallel to the east rift zone. The edge of the crater overhung a dark depth, estimated to be 75 m (250 ft) to the bottom by dropping a dozen pebbles and measuring their fall times.

The crater was first entered in 1923, when its opening was said to be about 10 m (30-35 ft) wide. William Sinclair, lowered on a rope down the throat, found that the shape was roughly that of an inverted funnel, widening with depth (see figure). He measured its depth as 78.5 m (258 ft) to the top of a rock pile, estimated to stand 10-12 m (35-40 ft) high. With a "measuring line," Sinclair determined the long diameter (parallel to the trend of the rift zone) as 67.5 m (222 ft). He likely draped the line over the talus pile, however, since he was in the dark by himself; if so, the real width of the crater was more nearly 60 m (200 ft).

The opening into the crater widened through the next 2-3 decades. This was noted at the time with photographs and sketches, and old-timers today talk about the crater getting bigger and bigger. Once jumpable by a horse, now it would take Pegasus. But was the crater itself widening, or only its surface entrance? The distinction is important for assessing its stability.

On September 22, 2006, the diameters of the crater were electronically measured as 50 m (164 ft) along the rift zone and 42 m (138 ft) perpendicular to the rift zone. The depth was determined with a measuring tape as 49 m (161 ft) below the west rim, the deepest point reachable with the tape. The center of the floor is probably several meters lower.

These measurements are quite different from those obtained by Sinclair but can easily be explained by collapse of the overhanging roof to widen the opening of the crater and decrease its depth. Today's crater dimensions, superimposed on the sketch made in 1923 (see figure), indicate that the walls of the crater have retreated little, if any; only the roof caved in, leading to the understandable but erroneous feeling that the crater was enlarging.

Devil's Throat has reached a stage in its development similar to that of Kīlauea's other pit craters, Halema`uma`u, and even the summit caldera. They all have vertical walls, circumferential fractures, and occasional rock falls. There is no reason to treat Devil's Throat any differently than the others. More rock falls will doubtless occur there, but the worst is over. Its intimidating name, no longer appropriate for a crater so wide open, could be changed in the interest of truth in advertising. Heavenly Dimple is one tongue-in-cheek suggestion.

Devil's Throat is the best, most obvious example of a collapse crater at Kīlauea and one of the best in the world. It should be a stop for any visiting group of geology students or any others wanting to learn how pit craters form by collapse, not explosion. Caution is advised, just as it is around the rims of other craters at Kīlauea. Sections of a crater's wall can topple at any time, as happened at Waldron Ledge in 1983. With care, however, Kīlauea's craters can be the source of enjoyment, education, and marvel.

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Volcano Activity Update

This past week, activity levels at the summit of Kīlauea Volcano have remained at background levels. The number of earthquakes located in the summit area has slightly increased (usually less than 10 per day that are large enough to locate), with the largest number located south and west of Halema`uma`u. Widening of the summit caldera, indicating inflation, continues.

Eruptive activity at Pu`u `O`o continues. On clear nights, glow is visible from several vents within the crater. Lava is fed through the PKK lava tube from its source on the southwest flank of Pu`u `O`o to the ocean. About 1 kilometer south of Pu`u `O`o, the Campout flow branches off from the PKK tube. The PKK and Campout tubes feed two widely separated ocean entries, at East Lae`apuki and East Ka`ili`ili, respectively. Both entries are located inside Hawai`i Volcanoes National Park.

In the last week, intermittent breakouts have occurred from the PKK tube just inland from the sea cliff at East Lae`apuki. Surface flows also have been active on the coastal plain along the west margin of the Campout flow, producing two lobes that were advancing toward the coast on October 6. One of these had stagnated by the 11th.

In the last week, several spatter cones in the crater and on the flanks of Pu`u `O`o have partially or completely collapsed. The most significant collapse occurred on the night of October 10, when a 50-60 m wide pit claimed most or all of the two spatter cones in the West Gap of Pu`u `O`o.

Access to the sea cliff near the ocean entries is closed, due to significant hazards. The surrounding area, however, is open. If you visit the eruption site, check with the rangers for current updates, and remember to carry lots of water when venturing out onto the flow field.

There were no earthquakes beneath Hawai`i Island reported felt within the past week.

Mauna Loa is not erupting. During the past week, earthquake activity remained low beneath the volcano's summit (seven earthquakes were located). Extension of distances between locations spanning the summit, indicating inflation, continues at slow rates. skip past bottom navigational bar