Update: February 16, 2008

HIDDEN

By Pam Eastlick for THE DEEP on line

Welcome to The Deep science and technology column where we cover topics from the deep sea to deep space and beyond.

Plume from Anatahan

Continuing its pattern of intermittent activity, Anatahan Volcano released more ash and steam on February 10, 2008. The MODIS on NASA’s Aqua satellite took this picture the same day. This picture shows the volcano plume meandering away from the volcano toward the northwest, spreading out as it goes.

A bulletin issued on February 10 by the U.S. Air Force Weather Agency states that an area of "vog" appeared some 90 nautical miles north of the volcano. Vog can form when pollutants from a volcano mix with oxygen and water in the presence of sunlight, and it is also known as volcanic smog. The 5.6-mile-long island of Anatahan is a stratovolcano composed of alternating layers of ash, lava, and rocks ejected by previous eruptions. The first historical eruption of Anatahan occurred in May 2003, forming a new crater inside the island’s eastern caldera. The lake inside Anatahan’s crater started to drain in October, indicating that a crack has opened in the caldera into the magma chamber below. Should an eruption open this crack to the ocean, there’s a possibility that the magma chamber would fill with millions of gallons of seawater and the incredible heat would instantly turn all that water to steam creating a very large explosion.

That’s what happened to Krakatoa 120 years ago and it could happen to Anatahan. Keep an eye on our steaming neighbor. Where ya’ gonna go when da volcano blow? I wrote a column about this when Anatahan started its current eruption phase and here’s what I had to say about the consequences for Guam. Could Anatahan erupt catastrophically like Krakatoa? Sure, it could. In fact, Anatahan is very similar to Krakatoa before its cataclysmic eruption in August 1883. Both islands had been blown apart before in massive eruptions and Anatahan has the same large caldera that Krakatoa had. Anatahan is a small island two miles wide and six miles long, but its crater is four miles wide. Anatahan is mostly crater. Krakatoa had a similar profile before 1883. Anatahan could ‘go Krakatoa’ on us. So, what does that mean for Guam? Well, since the volcanoes are similar, it might be a thought to examine just what happened when Krakatoa erupted and how widespread the devastation was. When Krakatoa blew up, the sound of the explosion was heard almost 4,000 miles away. It’s the loudest noise ever recorded. Here on Guam, we’ll know exactly when Anatahan blows (if it does), because we’ll hear it. So, if you hear something that sounds like an explosion or cannon or mortar fire, it just could be Anatahan. But here’s the important part. Anatahan is 200 miles from Guam. The maximum reach of lava, pyroclastic bombs (big rocks thrown out of the crater with incredible speed) and pyroclastic flows (ground-hugging avalanches of hot ash, pumice, rock fragments, and volcanic gas that rush down the side of a volcano as fast as 60 mph) from the Krakatoa eruption was 50 miles. We don’t have to worry about any of these things here on Guam. We’re too far away. Of course, you might be worried about that hundred foot tall wave generated by an Anatahan eruption that will destroy our whole island. Most of the people who died in the Krakatoa eruption died from the tsunami generated when the side of the volcano cracked open and seawater rushed into the magma chamber. The resulting steam is what actually blew the entire volcano apart. That could happen at Anatahan too. The crater is big and the bottom of it is now below sea level according to the scientists who monitor the volcano. If Anatahan does have a cataclysmic eruption, it could very easily generate a gigantic tsunami. But Guam is not vulnerable to tsunamis. A tsunami is a deep wave that must ‘run up’ an increasingly shallow sea floor. The sides of Guam drop off dramatically and almost vertically underwater. There is no place for a tsunami to gain height. A steam-generated wave could be quite large, but Anatahan is north-northeast of Guam. Any wave coming from that direction would hit the high, uninhabited cliffs that face the sea on all of northern Guam. I wouldn’t want to be on the beach up there if Anatahan blows, but you’d hear the explosion in plenty of time to head for higher ground. There is, however, one consequence of a cataclysmic eruption of Anatahan that we just might have to deal with and that’s ash. When Krakatoa erupted, it put twelve cubic MILES of ash, dust and pumice into the air. The ash and dust cloud completely covered the Sunda Straits and it was dark for around 20 hours after the eruption within a radius of 250 miles from the volcano. The darkness lasted more than 24 hours at places that were 130 miles away and over two days within a 50-mile radius of the volcano. In the immediate area, it was totally dark for three days. So, if Anatahan does erupt violently, prepare for ashfall and lots of it. You’ll be shoveling and shaking ash off things for a long time. And prepare to get cold, because if it’s dark for a while, things cool off pretty fast. If Anatahan blows, it’s highly unlikely that you will be injured or die, but likely that you’ll be inconvenienced for a while. Where ya gonna go when da volcano blow? I intend to ride it out right here. But I don’t think I’ll be visiting Saipan. The Anatahan magma chamber may be a hidden ticking time bomb but there are some other hidden things at the bottom of the Earth that are just now beginning to reveal their secrets.

WATER UNDERGROUND

A four-man British science team has begun exploring an ancient lake hidden deep beneath Antarctica's ice sheet. Lake Ellsworth could yield vital clues to life on Earth, climate change and future sea-level rise. The preliminary results show the lake of liquid water is 2 miles below the ice, 7 square miles in area and over 300 feet deep. This means Lake Ellsworth is a deep-water body and confirms the lake as an ideal site for future exploration missions to detect microbial life and recover climate records. Lake Ellsworth is likely to have been isolated from the surface for hundreds of thousands of years. Radar measurements made previously from aircraft surveys suggest that the lake is connected to others that may drain ice from the West Antarctic Ice sheet to the ocean and contribute to sea-level rise." Some 150 lakes have been discovered beneath Antarctica's vast ice sheet and so far little is known about them. They’re important for a number of reasons. For example, because water acts as a lubricant to the ice above they may influence how the ice sheet flows. Their potential for unusual life forms could shed new light on evolution of life in harsh conditions; lake-floor sediments could yield vital clues to past climate. They can also help us understand Europa (one of the moons of Jupiter), which may also have vast reserves of liquid water beneath a rock-like ice crust. Lakes and magma chambers aren’t the only things that are hidden however.

RECOVERING LOST ART

A huge and magnificent fresco by Leonardo de Vinci covers a 50-foot wide wall in the Palazzo Vecchio town hall in Florence. Also impressive are la America Tropical by the Mexican muralist David Alfaro Siqueiros in the Italian Hall in Los Angeles, and the numerous frescos adorning the ancient Hagia Sophia church in Bulgaria. Unfortunately you can’t see these paintings: they’re all hidden beneath a layer of plaster.

If studies by a team of scientists from the US and France continue to prove successful, however, then it could be only a matter of time before such frescoes, which have often been covered for religious or political motives, are exposed. Although plaster is opaque to visible light, in the much lower terahertz frequencies (1012 Hz) it all becomes clear. Their system involves scanning a pulse of terahertz light over a surface and then measuring how the amplitude of the reflected signal changes with time. Because materials have different properties, which determine how much light is reflected, these measurements can tell how dissimilar materials are layered on top of one another. This makes the technique ideal for imaging frescos — a technique in which pigments are painted into wet plaster. Although art historians regularly employ ultraviolet, infrared and Raman spectroscopy to examine the surfaces of murals, these techniques cannot probe deeper than a millimeter into plaster. On the other hand, X-rays and microwaves can penetrate many layers, but X-rays cannot distinguish between the layers and microwaves have a poor spatial resolution. Terahertz radiation has none of these drawbacks and, because it is non-ionizing, should not damage a painting either. The team has already tested the system on a graphite sketch of a butterfly embedded in a 4mm layer of plaster-of-Paris. After focusing the T-ray transceiver onto the back of the plaster, they found that they could make out the 2mm wide graphite lines of the butterfly. Their next step is to scan the St John the Baptist church in Vif, France, where there may be many hidden frescoes. Seeing the unseen. Ain’t science grand?

Cruise on over to the Deep Website at www.thedeepradioshow.com to explore many more hidden topics. Enjoy!