Mystery of the Megavolcano (2006).

Van Riper, A. Bowdoin

Mystery of the Megavolcano (2006)

Directed by Ben Fox

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Monster of the Milky Way (2006)

Produced and directed by Thomas Lucas and Julia Cort

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Mystery of the Megaflood (2005)

Produced and directed by Ben Fox and Joe Kennedy

Each DVD is distributed by PBS.org; www.pbs.org; 56 minutes

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Popular culture, along with high school science classes, leads us to expect that "real science" happens in the laboratory, where experiments can repeated time and again under the watchful eyes of scientists. Much of biology, chemistry, and physics does work that way, but large swaths of astronomy and geology do not. Astronomers and geologists routinely study phenomena and that, by nature--too big, too slow, too distant, too powerful - cannot brought to (or replicated in) a laboratory. They deal, as a matter of course, with events and processes to which no human observer can bear direct witness, and which no laboratory, however well equipped, can possibly duplicate. Just how geologists and astronomers do that is the subject of the trip of films reviewed here. Produced by PBS for its long-running science documentary series Nova they allow viewers to look over the shoulders of scientists working to make sense of phenomena whose power, scope, and intensity are--even for those used to thinking beyond normal human frames of reference--nearly unimaginable.

Mystery of the Megavolcano begins with the biggest volcanic event in recorded history: the 1815 eruption of Mount Tambora, which generated 12 cubic miles of magma and spewed so much ash into the atmosphere that 1816 became known as "The Year Without a Summer." Awesome as it is, however, Tambora is simply there for scale. The film's real subject is Toba, an Indonesian "supervolcano" that poured out 672 cubic miles of magma in a two-week-long eruption 74,000 years ago. It filled the air with pumice-rich ash and clouds of sulfur dioxide, producing climate change on a scale usually associated with asteroid impacts, and generating copious amounts of acid rain. Tambora altered the climate of Europe and North America for a year; Toba may have helped to precipitate the beginning of the last Ice Age.

A topic like this offers ample opportunity for breathless, lurid sensationalism: gruesome descriptions of victims suffocating as their lungs fill with ash and fluid, nightmarish visions of ash clouds smothering plants and blotting out the sun, and grim reminders (based on the existence of a supervolcano beneath Yellowstone National Park) that It Could Happen Here. Mystery of the Megavolcano touches on such subjects but does not dwell on them. Consistent with Nova's long tradition of emphasizing science rather than sensation, it focuses on a more mundane but more important question: "How, in the absence of eyewitness accounts, do we know that a catalcysmic eruption took place at Toba 74,000 years ago?"

The answer involves the work of three different scientists: climatologist Greg Zielinski, who found high concentrations of sulfuric acid in cores from the Greenland ice sheet; geologist Mike Rampino, who found evidence of a sharp temperature drop in ocean-floor sediments; and volcanologist John Westgate, who found a distinctive chemical signature in volcanic ash deposits from throughout Southeast Asia. The film is--again, in the Nova tradition--scrupulous in its depictions of the science. Its scenes of the scientists gathering and interpreting data are shot on location at field sites and in laboratories but they are never encumbered with the too familiar, never-convincing pretense that discoveries were being made (rather than simply explained) as the cameras rolled. Interspersed with these scenes are concise explanations of essential background knowledge. One particularly effective example describes how the oxygen atoms in tiny marine fossils known as foraminifera record temperature fluctuations in the deep ocean. The "fit" between the different lines of evidence is explained clearly and economically in the linking narration.

The film's only significant limitation has more to do with the subject matter than with the filmmakers' shortcomings. The scope of geological time is notoriously difficult to convey to non-geologists, and Mystery of the Megavolcano is no more successful at it than most documentaries about Earth history. The seventy-five thousand years separating us from the Toba eruption is nearly fourteen times the length of recorded human history, but less than half the lifetime of modern Homo sapiens and considerably less than one-thirtieth the lifetime of genus Homo. Geologically speaking, it is the blink of an eye. The film does little set the Toba eruption in this chronological context, and so to drive home just how common, by geological if not by human reckoning, such events are.

The problem of conveying the scale of geological events also hovers over Mystery of the Megaflood, but it centers on space rather than time. The flood of the title took place at the end of the last ice age: A lobe of the ice sheet that covered much of North America dammed the Clark Fork River near the present-day Idaho-Montana border. Water from the river backed up behind the ice dam, forming an inland sea bigger than Lakes Erie and Ontario combined. The vast body of water, dubbed Glacial Lake Missoula by geologists, extended 200 miles into western Montana and reached depths of 2,000 feet. It contained over 500 cubic miles of water that, when the ice dam broke, were emptied from it in less than 48 hours. The resulting torrent of water swept across Idaho and eastern Washington at speeds up to 65 miles per hour, scouring away tons of soil and carving a network of jagged, braided canyons deep into the landscape. Glacial Lake Missoula filled and emptied at least a dozen times over 2500 years, its cataclysmic floods shaping a section of eastern Washington known as the "channeled scablands."

Geologist J. Harlen Bretz, who studied the geology of the area for years in the 1920s, was the first to propose that the channeled scablands had been formed suddenly, by a catastrophic flood. It was he who pointed out that the scablands' undulating surfaces and incised, braided channels mirrored those that could be seen in streambeds everywhere. The difference was one of scale: the features were measured in meters, rather than millimeters, and cut into solid rock rather than soft sediment. Over time, Bretz came to believe that the most likely explanation of the channeled scablands' origin was a massive flood: moving water--just like that in thousands of stream beds--but on a scale orders of magnitude greater. He presented his theory at a special meeting of the Washington (state) Geological Society in 1929, but was roundly rebuffed by its senior members. The idea of a flood so vast, so sudden, and so powerful--capable of cutting ripple marks and channels into solid rock literally overnight--strained their credulity to the breaking point, and well past it.

Mystery of the Megaflood briefly introduces Bretz and his idea, then shifts to a brief reenactment of the meeting and the rejection. To their credit, neither the filmmakers nor the geologists who serve as "talking head" commentators denigrate Bretz's critics for failing to recognize the truth of his (now universally accepted) theory. They point out that geologists of the time believed, "on good evidence," in the power of gradual erosion to shape the Earth's surface, and associated cataclysmic floods with unscientific attempts to import Genesis into geology. They also note that, in 1929, Bretz had no inkling of the existence of a vast ice-dammed lake, and so no source for his hypothetical flood. One of the film's best moments is a description of geologist J. T. Pardee, who had inferred the lake's existence from studies of its long-dry bed, whispering to a colleague at the 1929 meeting: "I think I know where Bretz's water came from."

The story of the initial rejection and gradual vindication of Bretz's theories makes a fascinating case study of how (and why) scientific ideas change over time. It also serves as a prelude to the real story of Mystery of the Megaflood: how modern scientists, armed with Bretz's critical insight into the nature of the channeled scablands, and far more detailed knowledge of Glacial Lake Missoula than he or Pardee possessed, attempt to reconstruct the complex series of overlapping events that made much of the Pacific Northwest what it is today.

The vast forces unleashed by the breaching of Glacial Lake Missoula or the eruption of Mount Toba are, themselves, dwarfed by the those found in and near black holes. The forces created by the massive gravitational pull of black holes produce bizarre, results that confound our everyday understandings of how the universe is "supposed to" work. Black holes are zones of sheer, concentrated weirdness: difficult to study, and still more difficult to explain to a television audience with no special background in astronomy or physics. Monster of the Milky Way brilliantly overcomes the latter challenge in the process of showing how scientists overcome the former. The program breaks naturally into two roughly equal parts. The first is a primer on the nature and behavior of black holes. The second is a look at scientists' attempts to confirm the existence, and gauge the nature, of the titular "monster:" a massive black hole at the center of our galaxy.

The first part succeeds despite the fact that black holes are difficult to depict (their visual signature being the absence of light), difficult to conceptualize (what does it mean to "warp the fabric of space-time?") and difficult to think about in human-scaled terms (a black hole can emit energy equivalent to "a trillion trillion trillion atomic bombs"). Monster of the Milky Way handles these problems sophisticated computer animation to model the behavior of black holes, and an impressive group of commentators to provide verbal annotations. Fittingly, given the inescapable weirdness of black holes, the lineup of commentators includes two physicists who are also leading science fiction writers (David Brin and Gregory Benford) and a third known for sophisticated popular works on outre subjects like alternate dimensions and time travel (Kip Thorne). Most impressive of all, however, is Neil de Grasse Tyson, an affable astronomer from the American Museum of Natural History in New York.

Tyson's smooth delivery and gift for making outlandish ideas sound perfectly reasonable--talents that make him a natural heir to the late Carl Sagan--serve the program especially well. At one point, to illustrate the speed with which gravitational pull increases as an object moves deeper into a black hole, Tyson describes the plight of an astronaut who drifts into one. The difference in gravitational pull between his feet and his head (six feet away) would be sufficient, he notes, to tear the hapless astronaut in two. It is a mark of Tyson's rhetorical skill that the response evoked is not "Ick!" but the clearly-desired "Wow!"

The second part of the program is the kind of work that Nova crews have been doing for nearly thirty years: looking over the shoulders of working scientists, and asking them what they're doing and what they hope to find. Astronomy is particularly well-suited to this you-are-there approach, since the opportunities to make critical observations take place at predictable times in relatively accessible places. Not surprisingly, the segments of Monster that catch scientists in the act of being scientists are smoothly produced and engrossing. The occasional moments when they lapse into visual cliches (timelapse footage of observatory domes swiveling while clouds slip by and the sky darkens) are more than outweighed by the principal scientists' relaxed on-camera presence and ability to explain, on the fly, what the images on their computer screens are telling them. If journalism is, indeed, the "first draft of history," then Nova episodes could be seen as first drafts of episodes in a history of science yet to be written. Monster of the Milky Way is compelling support for that view, as well as compelling viewing.

All three films confront and, ultimately, meet one of the central challenges of effective science education: they encourage audiences to think about the natural world in terms radically different from those they are used to. Separately and together, the films reinforce Albert Einstein's famous dictum: "The universe is not only queerer than we imagine, it is queerer than we can imagine."

A. Bowdoin Van Riper

Independent Scholar