Sara Dosa’s Fire of Love is a tribute to Katia and Maurice Krafft, a geochemist and geologist who together revolutionised the world of volcanology. As the discipline’s pre-eminent couple, Katia and Maurice not only observed more volcanoes than any other scientists, but revolutionised the cinema of volcanoes, compiling “hundreds of hours of footage” and “a thousand photos” of some of the most extreme sites on the planet. Fire of Love is primarily a compilation of this footage, an attempt to evoke and condense one of the most remarkable bodies of work ever committed to film. Since Dosa only has ninety minutes at her disposal, Fire of Love often plays as a tone poem as much as a linear documentary, frequently recalling the more surreal edges of Werner Herzog’s oeuvre, and his passion for volcanoes in particular.

As a film couple, we meet Katia and Maurice first and foremost as a bridge between the post-war neorealism of the 50s and the various new waves of the 60s. Katia was born in 1942, and Maurice in 1946, and both describe their first loves as a pair of volcanoes that were precious to the neorealist imagination. For Maurice, it’s Stromboli, the site, subject matter and title of the first film in Roberto Rossellini’s trilogy with wife Ingrid Bergman. For Katia, it’s Etna, which towers over the village of Aci Trezza in Luchino Visconti’s La Terra Trema and, later, forms the backdrop for four of Pier Paolo Pasolini’s films – The Gospel According to St. Matthew, Theorem, Pigsty and The Canterbury Tales. The shift from neorealism to new wave that we see across those four Pasolini films is embedded in Katia and Maurice’s journey as well, starting with their shared childhood in the “postwar desecration of Alsace,” whence they evolve into a picaresque new wave troupe of two as they journey from volcano to volcano. Along the way, they reframe the 60s counter-culture in geological terms, becoming the cutting edge (pun intended) both of emerging plate tectonic theory and colour television, the perfect venue to remediate all the brilliant hues that they capture on photography and film.

Like the counter-culture, too, Katia and Maurice use volcanology to move away from conventional ideas of coupledom, especially those based on reproductive futurity. Instead, they decide not to have children on their honeymoon, proclaiming that “from hereon out, it will only be volcanoes, volcanoes, volcanoes.” Yet this shift from children to volcanoes doesn’t exactly reject reproductive futurity so much as transplant it to a more cosmic register, as Katia and Maurice attune themselves to the cycles of the mineral world rather than the biological world, and start to treat the earth itself as an organism they have to nurture: “What is it that makes its heart beat, its blood flow?” Excerpts from Brian Eno’s Another Green World start to trickle across the score, evoking a reproduction that is both organic and synthetic, divorced from the body even as it also embeds the body in more mechanical and impersonal rhythms.

Accordingly, Katia and Maurice are drawn to those sites where the earth is regenerating and perpetuating itself, where they revel in every conceivable threshold between solid and molten rock, every possible texture and consistency of magma. Birth takes on a more primal quality here, as they engage with the earth at its most protean, immersing themselves in the newest places on the planet, and mark them by cradling rocks that are only a couple of minutes or seconds old, juggling them from hand to hand as they cool and solidify. The plasticity and malleability of these thresholds between solid and liquid rock segue seamlessly into the first precarious footholds of new life, until the earliest stalks of plants, and the arrival of the first invertebrates, feel totally continuous with the sentience of the planet as a whole.

While these solid-liquid thresholds are of profound geological significance, Katia and Maurice experience them first and foremost as an incitement to cinephilia. Katia reflects that she’s trying to capture the perfect moment, whereas Maurice is trying to capture every moment, but in either case they envisage a synergy between the camera lens and that effervescent gap between magma moving and magma setting – an even more difficult threshold to conceive, let alone capture, because magma moves so fast, and sets so quickly. Trying to capture this junction is like trying to redress the fact that “the human eye cannot see in geological time,” as Katia and Maurice evoke this alien conception of time in the cusp between liquid and solid rock – the mercurial moment that lasts the arc of a volcano bomb, or an exploding magma bubble. As their cinephilic pursuit intensifies, they up the stakes further, searching for that sublime second when the earth is neither solid, liquid or gas, but all and none at once. They perhaps come closest to finding this in their extraordinary footage of volcanoes spewing magma along the Hawaiian coast. As molten rock emerges beneath the ocean, the water solidifies it at the very microsecond that it itself becomes gas, collapsing all clear coordinates.

Similarly, as their cinephilic quest intensifies, Katia and Maurice don’t just yearn to document the threshold between rock moving and rock setting, but to ride it, and inhabit it. Magma feels more fluid than water here, carrying all the motion of the planet in its passage, sliding and oozing with more viscosity and sensuality, and negotiating its relationship to solid matter with more dexterity than any liquid known to man. Hence Maurice’s dream of floating down a Hawaiian lava river on a canoe, as well as its precursor – his journey across the largest lake of sulfuric acid in the world, a jaunt so dangerous that Katia, as well as the other geochemists on their team, refuse to participate. This lake, which was potent enough to dissolve steel, exhibits the same volatile and visceral nexus between solid and liquid as the lava flows, but at first it seems to occurs in the opposite direction, since where volcanoes are continually generating solid from liquid, the lake operates by continually dissolving solids into liquids. Yet as Katia and Maurice focus on the acid solids that are accumulating on its shores, we realise that destruction and creation are synonymous in both volcano and lake, and that the planet is a continuous and tensile negotiation between solids and liquids that can never be resolved.

As a result, Katia and Maurice’s encounter with volcanoes is that of the sublime, a drive to “something beyond human understanding” and “that feeling of being nothing at all” that comes when “we contemplate living at the edge of the abyss; the phenomenon, restless, makes us shiver.” Sublimity brings on addiction – “once you see an eruption, you can’t live without it” – and whittles the couple down to the archetypal outlines of the ancient world, much as their primal quests to reach volcanoes, which are often just as dangerous as the volcanoes themselves, takes on the hue of classical myth, a raw encounter with the physical cosmos at its most elemental and primal. On the one hand, this creates a kind of Kantian mathematical sublime, in which the dimensions and complications of volcanoes only intensify with proximity: “Volcanology is a science of observation – the closer you get, the more you see.” Yet this very sublimity also shatters all mathematical and scientific discourse as well, leading Dosa to observe, in a paraphrase of Katia’s notes, that “no amount of science could have prepared them for this spectacle – instead, the language of mythology seems more apt.”

This sublimity also brings a profound sense of singularity that sets Katia and Maurice against the conventional classification of volcanoes, since each one has a “unique personality.” Insofar as they define volcanoes themselves, they do so aesthetically, identifying “red” volcanoes (those situated where plates are pulling apart) as the “nice ones” and “grey” volcanoes (those situated where plates are coming together) as the “killers.” We learn that the constant flow of lava in red volcanoes makes them “no more dangerous than walking on a road in Belgium,” while the inscrutability of grey volcanoes makes them more challenging.

Both the scientific and aesthetic challenges of volcanoes thus constellates around these “grey killers” in the second half of Katia and Maurice’s career. We see this presaged in their growing obsession with capturing and visualising the “geological scale” of the earth on film, which briefly takes them (aptly) to the language of the 70s acid western, which Dosa introduces just after the footage of Maurice crossing the acid lake. In a moment of auteurist abandon, they spend a “rationed reel of film” on a Jodorowsky-like spectacle of locals crossing a barren landscape, although this just turns out to be a preface to the pivot point of their career – the explosion of Mt. St. Helens in 1980. After a lifetime of getting as close to volcanoes as possible, and living alongside them like members of their own family, the couple can only experience this eruption retrospectively, by piecing together successive fragments of footage, including that of another volcanologist who perished on the mountain, and then spending several months amidst the wreckage in an effort to form a coherent picture of what happened there.

This brings us to the sublime kernel of grey volcanoes – namely, that their cusp between solid and liquid states is less discernible, since it’s buried beneath the ground, and less predictable, since it’s embedded in invisible geological rhythms, but also more catastrophic when it rises to the surface. Katia and Maurice’s cinephilic imperative now focuses on trying to capture the “trigger” point in these grey volcanoes when the magma becomes volatile enough for eruption – the seconds when liquid finally outweigts solid – by way of the profound silence that surrounds this whole process, itself such a stark contrast to the vivid gurgles and bubbles of red volcanoes. It’s a trigger point that can only be approached indirectly, and by personifying and aestheticizing the volcano, which grows “swollen,” gets “the shivers” and develops “bad breath” when eruption is imminent. Yet even when an eruption does occur, this sublime trigger point is immediately obscured by enormous plumes of smoke, the equivalent of twenty atomic bombs, powerful enough to overwhelm even a distant observer.

As it turns out, this is precisely what happens to Katia and Maurice on Mount Unzen in Japan, on June 3 1991, when a plume overwhelms and kills them. The final shot of them together comes from a camera that a journalist left running, as the last fragment of their cinephilic project is absorbed into the flow of the volcanoes they studied. Yet this cinephilic project, and self-destruction, is also a birth, and gift of its own, since the sheer tenacity of Katia and Maurice’s study of grey volcanoes – it takes them a year to get within fifty metres of an Alaskan pyroclastic surge – ends up creating massive gains in volcano prevention, preparation and protection, while saving hundreds of thousands of lives all around the world. All of these survivors are Katia and Maurice’s children, in a sense, born of their sublime fixation with volcanoes, and with grey volcanoes in particular, in all their silent and unknowable intensity.