Reprinted from here.
This plume, erupting from Halema`uma`u in 1934, is remarkably similar in appearance to the plume erupting from the crater today. USGS photograph.
The current volcanic activity in Halema`uma`u Crater is now Kilauea’s longest summit eruption since 1924. On November 25, 2008, it exceeded the previous record set in 1967-68, when lava erupted in Halema`uma`u for 251 days.
Newspaper articles tracking the 1967-68 eruption reported each time it reached a landmark length set by prior Halema`uma`u events. When it finally surpassed the 136-day record set in 1952, headlines touted the eruption as the second longest of the century.
Shortly after the 1967-68 eruption ended, Dr. Howard Powers, Scientist-in-Charge of the Hawaiian Volcano Observatory at the time, put its duration in perspective by noting that, historically, a summit eruption is the “normal” for Kilauea Volcano. He no doubt was referring to the 100-plus years of nearly continuous lava lake activity at Kilauea’s summit prior to 1924.
We use 1924 as a frame of reference for Halema`uma`u eruptions because, in the 19th and early 20th centuries, the crater looked nothing like it does today. It was an irregular landscape of craggy spires and islands with as many as four transient lava lakes.
In 1924, the long-lived lava lake drained, causing the crater walls to collapse and explosive eruptions that doubled the diameter of Halema`uma`u to about 900 m (3,000 ft). The crater looked much the way we see it now, except that it was over 400 m (1,300 ft) deep—almost five times deeper than it is today.
Since the fateful events of May 1924, Halema`uma`u has erupted 18 times. The first was just two months later, in July 1924, when an 11-day eruption formed a “puddle” of lava on the crater floor.
Over the next 10 years, six eruptions—in 1927, 1929 (two), 1930, 1931, and 1934—took place within Halema`uma`u. They varied in duration from 2 to 33 days, but each eruption added a layer of molten rock to the crater floor. With thicknesses averaging about 18 m (60 ft), these layers reduced the depth of Halema`uma`u to about 245 m (800 ft).
The end of the 1934 eruption marked the beginning of Kilauea’s longest period of quiet on record. For nearly 18 years, there were no eruptions anywhere on the volcano.
Kilauea made up for lost time when molten lava returned to Halema`uma`u in June 1952. The spectacular eruption went on for 136 days, with lava fountains sometimes visible above the crater rim. By the time it ended, the eruption had pumped more than 120 m (390 ft) of new lava into the crater.
During the next 30 years, Halema`uma`u erupted nine times—in 1954, 1961 (three), 1967-68, 1971, 1974, 1975, and 1982. These eruptions varied greatly in duration, from about 7 hours in 1975 to 251 days in 1967-68. The volume of extruded lava also varied, with the most—84.1 million cubic meters (110 million cubic yards)—erupted in 1967-68. Surprisingly, some of the shorter eruptions were quite voluminous.
Most of the rock covering the floor of Halema`uma`u today was emplaced during the short-lived 1974 eruption. Ten million cubic meters (13 million cubic yards) of molten lava quickly engulfed the entire crater floor, except for the tops of three high spatter cones from the 1967-68 eruption.
Each Halema`uma`u eruption that took place between 1924 and 2008 has its own unique story. Some are hair-raising, as in 1931, when a USGS engineer had to run for his life to escape sulfur dioxide fumes that overtook him at the crater rim. Most of them, however, describe activity strikingly similar to what we are experiencing today—gas emissions, ash-rich plumes, eruptions of frothy lava, and poor air quality.
The story of the 18th—and longest—Halema`uma`u eruption since 1924 is unfolding before our eyes. So far, it differs from the previous eruptions in that molten lava is not visible on the crater floor. Lava is close to the surface, though, as evidenced by ash, pumice, and spatter ejected to the crater rim and by a few rare glimpses of molten rock in the vent.
How long the current eruption will last and whether lava will flow on to the crater floor remain anyone’s guess. But, as of November 25, 2008, Halema`uma`u reached another milestone.
Kīlauea Volcano continues to be active. A vent in Halema`uma`u Crater is erupting elevated amounts of sulfur dioxide gas and very small amounts of ash. Resulting high concentrations of sulfur dioxide in downwind air have closed the south part of Kīlauea caldera and produced occasional air quality alerts in more distant areas, such as Pahala and communities adjacent to Hawai`i Volcanoes National Park, during kona wind periods. There have been several small ash-emission events from the vent, lasting only minutes, in the last week.
Pu`u `Ō`ō continues to produce sulfur dioxide at even higher rates than the vent in Halema`uma`u Crater. Trade winds tend to pool these emissions along the West Hawai`i coast, while kona winds blow these emissions into communities to the north, such as Mountain View, Volcano, and Hilo.
Lava continues to erupt from the Thanksgiving Eve Breakout (TEB) vent and flow toward the ocean through a well-established lava tube. Lava breakouts in the Royal Gardens subdivision have been active throughout the past several weeks, sending flows onto the coastal plain. As of Monday, December 1, these active flows were within 200 yards of the National Park boundary. Activity at the Waikupanaha ocean entry continues, with occasional small explosions. A deflation-inflation cycle began at the summit early on December 4, and was still ongoing at the time of this writing (afternoon of December 4). These cycles normally cause short-term fluctuations in lava supply to the flow field.
Be aware that active lava deltas can collapse at any time, potentially generating large explosions. This may be especially true during times of rapidly changing lava supply conditions. Do not venture onto the lava deltas. Even the intervening beaches are susceptible to large waves generated during delta collapse; avoid these beaches. In addition, steam plumes rising from ocean entries are highly acidic and laced with glass particles. Check Civil Defense Web site (http://www.lavainfo.us) or call 961-8093 for viewing hours.
Mauna Loa is not erupting. One earthquake was located beneath the summit this past week. Continuing extension between locations spanning the summit indicates slow inflation of the volcano.
No earthquakes were felt on Hawai`i Island in the past week.
Visit our Web site (http://hvo.wr.usgs.gov) for daily Kīlauea eruption updates, a summary of volcanic events over the past year, and nearly real-time Hawai`i earthquake information. Kīlauea daily update summaries are also available by phone at (808) 967-8862. Questions can be emailed to askHVO@usgs.gov.