This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

Friday, March 13, 2015

The "Vanuatu Monster" storm

From CNN

From Wiki

First of all, where is and what is Vanuatu? It's an island nation of volcanic origin in the South Pacific some 1000 miles east of northern Australia. If you subscribe to the USGS earthquake notification system, you'll see a lot of alerts about earthquakes near Vanuatu. 65 of Vanuatu's 82 islands are inhabited. The islands are steep, prone to landslides and slippages, and there is little permanent fresh water. The shorelines are rocky and drop quickly into oceanic depths because there is no continental shelf. The active volcanoes are Lopevi and Mount Yasur, with eruptions (undersea) recorded in 2008, and another in 1945. About 267,000 people inhabit the islands. Many people live on less than $1/day, and the infrastructure is weak.
Four cyclones at once

Although two cyclones in the same basin at the same time is not uncommon in the Atlantic or Pacific, four storms at once is rather rare. There are currently four simultaneously in the southern Pacific: Olwyn, Nathan, Bavi and Pam. There have only been four simultaneous hurricanes at once in the Atlantic two times, in 1893 and 1998.* The 1893 hurricane claimed between 1000-2000 lives in Georgia and South Carolina.

Pam, at category 5, is the strongest storm to make landfall since Haiyan hit the Philippines in 2013. Pam has already hit Port Vila, the capital of Vanuatu, a city of 44,000 people. It is likely to hit southern Vanuatu islands early Saturday morning local time. Pam has sustained winds of 165 mph, but as of the time of this writing (Friday, 1:00 PDT which I think is Saturday at 1:00 a.m. in Vanuatu) the reported gusts have been 60 mph. Storm surge and "very rough to phenomenal seas" are expected to affect particularly the central and southern islands.

It's a bit difficult to know what to believe about barometric pressures, as there are no reconnaissance aircraft in the vicinity. Pressures in the eye have been reported to be as low as 870-890 mbar's. If true, the 890 mb is lower than all known hurricanes except Wilma in 2005 (882 mbar's) and Gilbert in 1988 (888 mbar's).  The lowest pressure ever recorded was Super Typhoon Tip (870 mbar's) in 1979.

Why four at once?* There is a wet/dry cycle of 30-60 days known as the Madden-Julian Oscillation, a wave of atmospheric energy that moves east near the equator over these time scales. In one phase, upward motion in the atmosphere is strong, a condition that boosts the formation of thunderstorms. This is the condition now in the western Pacific.This, combined with a strong burst of westerly near-surface winds just south of the equator in the same region this week gave a "boost" to any low-pressure systems trying to get fired up. The result: four storms. See the reference at *, and links within it, for more discussion.

My prayers and thoughts are with the people of Vanuatu as you recover from this storm.

* Discussion from http://www.weather.com/storms/typhoon/news/four-tropical-cyclones-pacific-australia

Wednesday, March 4, 2015

Villarica volcano, Chile, eruption

Villarica eruption March 3, 2015.
AP Photo/Aton Chile
Villarrica volcano is one of Chile's most active volcanoes. It lies along the crest of the Andes in southern Chile, at the west end of three stratovolcanoes that trend perpendicular to the Andes along a fault. The lava is basaltic-andesite and the eruptions are typical Strombolian eruptions that eject pyroclasts several kilometers into the air and lava flows. In 1964 and 1971 massive lahars accompanied the eruptions because of rainfall and melted snow and ice. The current eruption began on February 7th and over 4,000 people were evacuated, but most have returned home as of today as the eruption has waned.

Villarrica has a persistent lava lake in the bottom of a summit crater. It is ~40 m diameter, and in the early 2000's, it ranged from about 20-100 m below the summit crater rim.  In 2004, abundances of gases were measured by Shinohara and Witter, and found to consist of H2O, CO2 and SO2. The gas emissions were the same in the continuous emissions as in lava spattering events, suggesting that the degassing occurs at very shallow levels and that the lava spattering is caused by the bursting of bubbles formed under equilibrium conditions in the magma.
     In 2000, in response to a regional seismic event, the eruption of a small volume of lava apparently plugged the conduit (Ortiz et al., 2003) on September 22. On October 5 and 8, a series of explosions reopened the conduit. Ortiz et al. found that the frequency of the harmonic tremor caused a shift in the peak frequency of the tremor from 1 Hz (open conduit) to 2 Hz (closed conduit). (Aside: This is interesting because it is the opposite of normal pipe behavior for which open pipe frequencies are twice the closed pipe frequencies.)
     In a textural and geophysical study conducted over a 10-day period in 2004, Gurioli et al (2008) found two types of pyroclasts: scoria and "golden pumice." They have identical glass compositions, but different textures, and the authors concluded that they underwent different histories in the conduit.  They interpreted the golden pumice as rising in the expanding inner part of the eruptive jet, and the scoria as forming the outer portion of the jet.  The scoria was entrained during passage of fresh material (that became the golden pumice) through older material in the upper portion of the conduit.


Shinohara and Witter, Geophysical Research Letters, 32(20), L20308, 5 pages, 2005
Ortiz, et al., Journal of Volcanology and Geothermal Research, 128 (1-3), pp. 247-259, 2003.
Gurioli, et al., Journal of Geophysical Research: Solid Earth, 113(B8), B08206, 2008.