Showing posts with label plume. Show all posts
Showing posts with label plume. Show all posts

Wednesday, July 8, 2009

The beginning of a new era—Kilauea's 1952 summit eruption

Reprinted from here.

Halema'uma'u 1952:
Halema'uma'u 1952:

A single low lava fountain emitted a steady stream of gas when photographed by Fred Rackle on July 21, 1952, when Halema`uma`u Crater was more than twice as deep as it is at present. View is to the southwest.

The HVO Web site was recently revamped to make access to our increasing number of Webcams easier for About 20 minutes before midnight on June 27, 1952, almost exactly 57 years ago, Mrs. John Fox walked from the living room of her home on the east rim of Kilauea caldera into an adjoining room. She was instantly startled by a loud, whistling roar coming through an open window. Running back into her living room, she saw a bright orange glow lighting the night sky.

At about the same time, just down the road at Kilauea Military Camp (KMC), Colonel B.W. Rushton pointed out the bright glow to Hawaiian Volcano Observatory (HVO) staff member John Forbes, who quickly called Gordon Macdonald, then Scientist-in-Charge of HVO.

When John Forbes arrived minutes later at HVO, on the edge of Kilauea caldera, he was greeted by the top of a huge lava fountain rising above the rim of Halema`uma`u. The crater was then nearly 245 m (800 ft) deep—more than twice its current depth from the rim to the crater's floor. By the time Gordon Macdonald arrived at HVO some 10 minutes later, the fountain was no longer visible, but incandescent fragments could still be seen arcing out of the crater.

Quickly grabbing the necessary equipment, Macdonald and Forbes set out by car for Halema`uma`u Crater to make detailed observations. As they followed Crater Rim Drive down onto the western floor of Kilauea caldera—the section of road that is closed today due to ongoing summit activity—they encountered a choking, sulfurous fume cloud so thick that they could barely see the road.

The fall of tephra onto the road was so heavy that they were hard-pressed to keep the car moving forward as it plowed through the drifts of pumice. The hail of tephra onto the car, with pieces reaching up to 10 cm (4 inches) across, sand-blasted the car's exterior to the point that it later had to be repainted and have its windshield replaced.

Pressing onward, Macdonald and Forbes passed through the tephra fall and quickly walked to the southeast rim of Halema`uma`u, reaching it about 10 minutes past midnight. When they peered into the crater, they saw a continuous line of lava fountains, 790 m (2,600 ft) in length, crossing the entire crater floor from southwest to northeast and extending part-way up the northeastern crater wall.

For the most part, the individual fountains were 15 to 30 m (50 to 100 ft) in height, but a fountain 120 m (400 ft) high jetted up near the bottom of the southwestern wall of the crater—probably a diminished version of the same fountain, at more than 245 m (800 ft) in height, seen minutes earlier from HVO.

Though views were poor due to the heavy fume, brief glimpses of the crater floor showed that older spatter cones on the floor of Halema`uma`u had already been buried beneath a rising lava lake. This suggested that more than 3 million cubic meters (4 million cubic yards) of lava were erupted in the first half-hour of the eruption. It would take about six days for Kilauea's current east rift zone eruption to pump out that much lava today.

The eruption rate quickly declined after the initial outbreak, but lava fountains continued to play on the surface of the lava lake over the following weeks. By late summer 1952, activity had begun to decline, but the eruption persisted until November 10, when the last fountaining activity was observed.

Having erupted for 136 days, the 1952 summit eruption brought to an end, in grand fashion, any doubts as to whether or not Kilauea was still alive. Prior to 1952, Kilauea had been quiescent since October 1934, when the previous summit eruption had ended, and some had begun to think that Kilauea was dead. But frequent earthquakes and the occasional swelling and shrinking of the volcano over the intervening years told volcanologists otherwise. It was no great surprise, then, when the eruption finally occurred.

Followed by dozens of eruptions in the years since, the 1952 eruption undoubtedly ushered in the current era of volcanic activity at Kilauea. Today's ongoing summit and east rift zone eruptions are just the most recent in the string of eruptions that have followed since Mrs. Fox was surprised by the glow outside her living room window.

Kīlauea Activity Update

Surface flows in the Royal Gardens subdivision may have stagnated early this past week in response to a deflation-inflation (DI) event at Kīlauea's summit. Smoke continues to rise, however, from forested kipuka in the subdivision, indicating that at least some burning continues. At the coast, the Waikupanaha and Kupapa`u ocean entries remain active and continue to produce prominent plumes, accompanied by small littoral explosions, as lava spills into the ocean.

At Kīlauea's summit, the vent within Halema`uma`u Crater is still emitting elevated amounts of volcanic gas, resulting in high concentrations of sulfur dioxide downwind. Glow from the vent was visible at night through the past week, and rare views into the vent by HVO scientists found that the lava surface is still present about 205 m (675 feet) below the floor of Halema`uma`u Crater.

No earthquakes beneath Hawai`i Island were reported felt this past week.

Visit our Web site (http://hvo.wr.usgs.gov) for detailed Kīlauea and Mauna Loa activity updates, recent volcano photos, recent earthquakes, and more; call (808) 967-8862 for a Kīlauea activity summary; email questions to askHVO@usgs.gov. Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey's Hawaiian Volcano Observatory.

For more information on traveling to Hawaii in general and exploring the Big Island's volcanoes in particular, please also visit www.tourguidehawaii.com and www.lovingthebigisland.wordpress.com.

Monday, June 8, 2009

Volcano Update: Magma within Kīlauea's summit vent never goes flat

Reprinted from here.

Magma within Kīlauea's summit vent never goes flat

On May 14, a brief bit of clear weather shows the Halema`uma`u plume rising and blowing with the wind.
On May 14, a brief bit of clear weather shows the Halema`uma`u plume rising and blowing with the wind.

Two weeks ago, readers of this column learned about the genesis of brown plumes and sudden gas release from Kīlauea's summit vent. This week we will continue that exploration, looking farther into Kīlauea's magma plumbing system to explain why the summit vent has become a long-lived feature of the volcano.

As residents of the Big Island can attest, vog has been a substantial irritant since the formation of Kīlauea's summit eruptive vent in early 2008. Can we expect this release of volcanic gas to go away anytime soon? The short answer is no, but that requires a bit of explanation.

As magma rises to shallow levels beneath the ground surface, pressure on the magma drops, and gas is released—similar to opening a can of soda (dropping pressure), allowing the dissolved carbon dioxide to bubble out. The magma will go flat once all of the gas is released, suggesting that Kīlauea's summit should eventually stop releasing gas.

The persistence of volcanic gas emissions from Kīlauea's summit is evidence that the supply of gas-rich magma is being replenished. To understand why, we’ll need to understand the principle of convection—in other words, how a lava lamp works.

In a lava lamp, heat added at the bottom warms the colored blobs within the lamp, causing them to become less dense and rise to the top. Since the top of the lamp is away from the heat source, the colored blobs gradually cool, become denser, and sink. The cycle repeats itself until the lamp is turned off.

A similar process is probably occurring beneath Kīlauea's summit but is driven by gas release instead of by heat. Magma within the summit vent is like an open soda, where dissolved gases gradually come out of solution. As the magma goes flat, its density increases. Eventually, the dense, flat magma will sink and be replaced by less-dense, gas-rich magma—a lava lamp in action! As a result of this process, the summit plume of gas and ash is constantly renewed.

Besides the unusual persistence of the summit plume, there is other evidence that convection is occurring within Kīlauea's shallow magma system.

If you read the Kīlauea daily activity updates, posted on the Hawaiian Volcano Observatory (HVO) Website each morning, or are a regular reader of this column, you’ve probably heard of “DI” events. “DI” is shorthand for “deflation-inflation.” These events occur as the summit suddenly begins to deflate and then, after about 12–48 hours, just as suddenly begins to inflate and returns to normal.

Prior to 2008, the average number of DI events occurring in any given year was about 10. In 2008, however, there were 47 DI events and, in 2009, there have already been 15 thus far.

DI events may be a physical manifestation of convection within Kīlauea's shallow magma plumbing system. DI deflation could be caused by downward flow of dense, “flat” magma, with DI inflation representing the rise of fresh, gas-rich magma. During the time between DI events, fresh magma would gradually degas and become denser. The increase in the frequency of DI events in 2008 probably reflects the fact that, due to the start of the summit eruption, the magma rose to very shallow depths, allowing for much more efficient and rapid degassing.

Vent collapses, like the one that generated the spectacular brown plume in early May, are sometimes associated with DI events. Assuming that DI deflation signifies the downward flow of dense magma, collapses might be expected, due to removal of magmatic support from the eruptive vent.

Although magma convection is suspected at several volcanoes worldwide, the process is difficult to document, because there is no way to see directly into a magma chamber. At Kīlauea, however, the outstanding level of geophysical and geochemical monitoring has provides good evidence of convection just beneath the volcano’s surface.

Scientists at HVO will continue to study DI events, gas emissions, brown plumes, and other signals from the summit vent in hopes of learning more about Kīlauea's magma plumbing system. There is no doubt that this lava lamp will be going for a long time to come, so stay tuned to this column and the daily activity updates for the latest information!

Kīlauea Activity Update

The Waikupanaha and Kupapa`u ocean entries remain active and are topped by robust laze plumes. Frequent small collapses have prevented either entry from building a large delta. There have been no lava breakouts from anywhere along the tube system reported in the last week.

At Kīlauea's summit, the vent within Halema`uma`u Crater continues to emit elevated amounts of sulfur dioxide gas, resulting in high concentrations of sulfur dioxide downwind. Glow, gas-rushing noises, and the emission of juvenile ash during the past week suggest that a small lava lake is still present below the floor of Halema`uma`u Crater.

No earthquakes beneath Hawai`i Island were reported felt this past week.

Visit our Web site (http://hvo.wr.usgs.gov) for detailed Kīlauea and Mauna Loa activity updates, recent volcano photos, recent earthquakes, and more; call (808) 967-8862 for a Kīlauea activity summary; email questions to askHVO@usgs.gov. Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey's Hawaiian Volcano Observatory.

For more information about traveling to Hawaii in general and touring the Big Island in particular, please also visit www.tourguidehawaii.com and www.lovingthebigisland.wordpress.com.

 

Casino Bonus no Deposit