A wisp of steam curls lazily above the volcano’s peak. The ground murmurs and groans. The mountain’s slopes bulge ominously. Is the volcano ready to blow? Or is it just restless, and years — or perhaps centuries — away from a potentially dangerous eruption?

Scientists working in Hawaii and elsewhere are using more sophisticated tools than ever to try to predict the behavior of volcanoes. NATURE’s Violent Hawaii offers a glimpse of some of these tools, such as special scoops to collect lava samples. But volcanologists have a lot more gear stored in their toolboxes. Here’s a sampling:

Tiltmeters

Scientists use tiltmeters to measure extremely subtle changes in a volcano’s slope. An increasingly steep side, for instance, can indicate a buildup of gas and molten rock inside the mountain, making it swell. Modern tiltmeters can detect a change of just one part per million; that’s equivalent to being able to detect someone lifting the end of a half-mile-long board just one millimeter — or about the height of a dime.

Gas Samples

A geologist cools a sample of molten lava in a can of water.

The gas emanating from a volcano’s vents and crater can tell scientists a great deal about what is happening deep beneath the earth. Changes in concentrations of carbon and sulfur gases might signal the arrival of a new batch of magma, or molten rock. The amount of malodorous hydrogen sulfide gas may also indicate an impending eruption.

Obtaining gas samples can be dangerous. A spectrometer — an instrument that analyzes light coming through a volcanic plume — allows scientists to conduct a study from a safe distance. Since each type of gas emits its own distinctive light signature, researchers are able to identify what is coming out of the volcano. In 1991, such gas analysis tools helped researchers predict the eruption of Mount Pinatubo in the Philippines, saving countless lives.

Thermal Imagers

Special cameras carried by aircraft or satellites can take pictures of the heat emitted by volcanoes. These “thermal images” help researchers identify new lava flows (which are hotter) and older, cooler ones.

Seismic Monitors

Monitoring a mountain’s seismic activity was one of the first methods used to predict volcanic eruptions. An increase in earthquakes can be a sign of an impending eruption. Researchers use seismic monitors to track the many small tremors that occur around a volcano. Modern seismometers can record the intensity, escalation, and epicenters of earthquakes. In Hawaii, researchers have more than 60 seismic monitoring stations on the Big Island alone.

Radar Mapping Instruments

Radar mappers carried by aircraft and satellites produce remarkably detailed three-dimensional maps of the Earth’s surface. They help researchers predict where lava flows might travel — or predict the path of the incredibly dangerous steaming mudslides produced by some volcanoes. Local officials can then use this information to evacuate threatened areas in the event of an eruption.

The Hawaiian chain of islands, made up of six main islands plus two smaller ones, stretches for more than 1,500 miles through the heart of the Pacific Ocean. It is a place of idyllic beauty. But it is also a land of volcanic fury, raging mountaintop blizzards, dangerous rockslides, monster waves, and even tsunamis.

Kilauea, on the Big Island of Hawaii, provides the most dramatic display of volcanic power. The volcano’s newest cone, Pu`u `O`o regularly spews molten rock and its steady flow of lava in the past two decades has added more than 500 acres to the island.

High above the sea at nearly 14,000 feet is Mauna Kea, which rises above 40 percent of the Earth’s atmosphere, making for ideal stargazing. The summit of Mauna Kea is usually barren and dry, but in the winter the crest experiences blizzards with winds that whip up to 70 miles an hour.

When a blizzard rages on Mauna Kea, chances are good that down at sea level, it’s pouring. Torrential storms are common and can be very destructive. On Oahu, one community found itself in peril after tons of rock rolled down from the hills above. A veil of steel mesh was used to contain the hillside. It will keep the rocks in check for now, but erosion is an inevitable part of the natural order.

On the north shore of Maui waves that originate as far away as Siberia sometimes rise to as much as 70 feet as they break here, earning both the waves and the beach the nickname “Jaws.” Monster waves like these are seen rarely, but lifeguards are vigilant in their efforts to spot them because they can swallow a person in an instant. Still, surfers come from all over the world for a single ride on these shores that may last less than half a minute.

Far deadlier than the waves at Jaws are tsunamis. These fast-moving walls of water are triggered by earthquakes or landslides and have killed more people in Hawaii than any other natural disasters.

NATURE’s Violent Hawaii reveals a tropical paradise shaped by the most brutal forces of the natural world.

To order a copy of Violent Hawaii, please visit the NATURE Shop.

Content for Violent Hawaii was originally posted January 9, 2005.

This episode premiered March 29, 2008.

Have questions for Kevin? Submit them here.

Featured in Kilauea: Mountain of Fire, Milton Garces records infrasound in order to better understand what’s happening in Kilauea’s underground lava tubes. NATURE spoke with him in March 2009.

Q: Tell us a bit about ISLA, the Infrasound Laboratory, and its mission.

A: We are located on the western tip of the Big Island of Hawaii. The lab’s main function is to operate listening stations as part of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty. Beyond that we conduct research on volcanoes, ocean waves, storms, and have recently deployed a hydroacoustic station.

Can you give a brief description of what causes infrasonic tremor and where the infrasound is physically emitting from?

Numerous sources at Kilauea could be producing the tremor. As the magma rises to the surface, pressurized gas comes out of the magma. The release of this gas causes pressure fluctuations, or infrasound. Anywhere pressurized gas is being released is a possible source of infrasound. Halemaumau is currently the loudest source of infrasonic tremor at Kilauea. Gas bubbles, both large and small, are involved in producing the sound at Kilauea. They can even excite large underground cavities into resonance, just like blowing over a beverage bottle or ringing a bell.

How long have you been listening to Kilauea?

ISLA’s first deployment was in 2002. Since then we have had continuous recordings using numerous stations since 2006.

Has anyone else done this before—recorded the infrasounds of lava flow?

Volcano infrasound research actually began with the eruption of Krakatoa in 1883. However, the past 20 years has seen the majority of volcano infrasound studies. Numerous volcanoes all over the world have been found to produce a significant amount of infrasound. Kilauea, however, has its own unique voice and we have captured a wide variety of signals from it, from tremor, explosions, lava skylights, fissure eruptions, and bench collapses.

Humans can’t hear the sounds coming from the volcano because they are at such a low frequency, but are there any organisms you know of that can detect Kilauea’s infrasound waves?

I know many animals communicate and hear infrasound (such as elephants), but am not aware of any organisms on Hawaii that would be able to hear infrasound from Kilauea. With that said, the higher frequency audible sounds would be heard by many.

Milton Garces listens to infrasonic recordings on a computer

What do you think the future applications of volcanic infrasound research may be?

I think the continued integration of infrasound with other technologies (such as seismic and satellite observations) will greatly help us understand and monitor volcanoes in the future. For example, we have a project in Ecuador right now where we are using infrasound and satellite observations to identify ash-rich volcanic eruptions, in hopes of providing early warning to aircraft operations in the region.

Can infrasound research be used to predict future eruptions?

Rather than focus on prediction, infrasound can tell us what is going on at the volcano right now and whether an eruption is occurring at that moment. Volcanoes are such complex systems that prediction is difficult. Gaining a more complete understanding of what is happening right now and what has happened before probably gives us the best chance for mitigating hazards.

What was your process of setting the microphones and what problems if any did you encounter as you did so?

First we had to select a good location — this is key to obtain good infrasound recordings. The dense jungle forest around Kilauea provides a great location as it shelters us from the wind. Then we needed to find a way to send our data back to our lab in Kona in real-time. From there the installation of the microphones is fairly simple, as we have a set design for our portable deployments. Luckily we have had no major equipment or data problems. Part of this can be attributed to the fact that we are able to record from long distances. Placing microphones next to active volcanoes often increases the likelihood of them being destroyed by the volcano, which is a main reason why we prefer to record from five to ten miles away.

What can infrasound measurements tell us that seismic data cannot?

Seismic data can tell us about magma moving underground, while infrasound is produced when there is pressure released at the surface. This way infrasound can help distinguish between subsurface and surface activity. Lots of seismic activity does not necessarily translate to lava or gas at the surface, but infrasound does. Also we often put out an array of microphones, kind of like an antenna, to determine what direction the sound is coming from.

Does Pele ever stop chanting? Will she ever?

Pele takes short breaks now and again, but she has remained active. Even if she were to take a break at Kilauea, it is likely that she would begin again in the relatively short future. Also, don’t forget Mauna Loa volcano is right next to Kilauea and has erupted numerous times in recent history, and when it does, we will be ready to record its unique voice.

Listen to the recordings (will open in a new browser window):

• Spattering Vent at Pu’u O’o in June 2007
• Collapse and Shutdown of Pu’u O’o in June 2007
• Opening of the Halemaumau Gas Vent in March 2008

Go to the ISLA Web site for more information.

Ejecting fire, molten rock, giant boulders and poisonous gases, the volcano can be a hazard for researchers, homeowners, plants and animals, but it doesn’t just leave destruction in its wake. Twists and turns in the lava’s flow leave some patches of original ecosystems, called kipukas, undisturbed. These oases of life provide a haven to many rare creatures — including the Hawaiian state bird, the Nene — but remain in constant danger from the volcano and from invasive species. Below the surface, inactive lava tubes provide homes for many unique species of darkness-loving creatures called troglobites.

At the end of its journey, the lava meets the ocean. Braving an extremely hot sea, filmmakers record the birth of new land and the incredible phenomenon of pillow lava – a bizarre and truly magical sight to behold.

Violent and beautiful, destructive and creative, Kilauea: Mountain of Fire explores the incredible power of the volcano and the challenges of life in its shadow.

Kilauea: Mountain of Fire premieres Sunday, March 29 on PBS.

Being in the wrong place at the right time is a necessity when filming volcanoes. Unlike wild animals that tend to run and disappear at the first sight or smell of a human, lava flows are unpredictable, quite dangerous — and they come right at you.

Good thing I wasn’t around for the filming of this extraordinary sequence of lava dripping into the ocean, where it expands, pops, and explodes for our upcoming film on Hawaii’s Kilauea volcano. Emmy award-winning cinematographer Paul Atkins took his HD camera underwater to capture this rare event. He had to brave ocean water temperatures of 100 degrees to film fire underwater. First, check out the footage:

Here’s Paul’s account of the experience:

A Rare Opportunity

Normally, quality underwater images of lava entering the sea on the “Big Island” of Hawaii are next to impossible to obtain. Once the lava really gets pumping in a location, the scene below the surface is too unstable and dangerous, and the water visibility is reduced to almost zero. As the flow continues, the lava hardens and forms a massive “bench” that periodically collapses — certain death for any divers caught in the ensuing underwater turbulence.

Catching the Flow

The key is to catch a lava flow in its early stages before a bench forms, within the first few days of entering the sea.

In this case, the ocean-entry lava flow had stopped for several weeks. Suddenly, a fresh surface flow rolled down Kilauea and began to sizzle into the ocean again. The sea bottom at this spot was relatively old, meaning it had not experienced a lava flow since the early 1980s. This, combined with clear, calm weather on a usually turbulent coast, was the special set of conditions for which I had waited 25 years.

The first challenge was picking a place to position our boat and enter the water. Out in front of the flow, the ocean surface was steaming hot — as much as 100 degrees fahrenheit in places. A few feet beneath this scalding layer, however, the water was much cooler. The plan was to slip under the hot layer and swim in the cooler water toward the lava flow at the coast, navigating by compass if necessary.

Getting Out

In a way, lava diving is similar to ice or cave diving. In an emergency — if you run out of air, for instance — you can’t make a vertical ascent and come up. There’s a ceiling of scalding hot water looming above. You must save enough air to navigate out from under this ceiling before you can surface.

Our filming went well on the first dive, and we got fantastic shots of bizarre pillow lavas forming and exploding in clear, blue water. We thought we saved enough air pressure, 500psi, to make it out. But as we swam toward our boat, we realized we had a problem. Each time we attempted to come to the surface — sticking one hand up to test the temperature — it was too hot and we had to retreat. We kept trying for 100 yards out. Nothing. The scalding hot ceiling had expanded while we were down under. We couldn’t come up for air, and my air pressure was down to next to nothing, less than 20psi.

For a moment, I thought the rare footage we had just shot would never see the light of day. I looked at my dive buddy, Richard Pyle, and we just shrugged. No choice. We went up through the hot water. By some miracle, we surfaced in a cooler spot — I don’t know where it came from. It was hot enough to steam up our masks, but not enough to boil skin.

Thanks, Paul.

- Fred Kaufman
Executive Producer