Despite their scientific value, when the leaves were excavated they were not the reason for digging. The focus was on their surrounding matrix, the rest of the rainforest that had condensed into the dark combustible substance we call coal. Unlike Scott Morrison’s lacquered black coal, this coal was brown, meaning that it was only partly dried out, its transformation from rainforest incomplete. From a resource perspective, this lignite is a ‘low rank’ product suitable only for local combustion to release its millennia of sunlight.

The area where the coal was being mined and burnt was the bushland behind the coastal town of Anglesea. Just on the margins of the Otway Basin coal reserve, the site was chosen for its proximity to Geelong, because the resultant electricity was destined for an aluminium smelter at Point Henry. The owner of both was Alcoa, the Aluminum Company of America, which commenced in Australia in 1961 as part of a global corporate expansion designed to stimulate the mass production and consumption of domestic and manufacturing products. Australia offered Alcoa a welcoming governance environment and seemingly copious amounts of the two main ingredients that aluminium requires: bauxite and electricity. Bauxite is an attractive, highly weathered rock that Alcoa continues to mine in Western Australia, just as Rio Tinto does within the subtropical forests of Queensland, helping make Australia the largest bauxite exporter in the world, despite the low grade of much of its resource. Producing masses of waste sediment, the spotted rock is crushed and mixed with caustic soda in an energy-intensive process to produce a white powder, alumina. Alcoa ships its alumina around the Great Australian Bight to Victoria, some going to the smelter at Portland on the western coast, and some to Point Henry, where, with the help of nearly twenty per cent of Victoria’s electricity, it is transformed into aluminium. That was until the Point Henry smelter, as well as an aluminium recycling plant and two associated rolling mills (which turned aluminium into cans), were closed in 2015 amid, among other things, a dispute with the Loy Yang coal-fired power station in the Latrobe Valley over energy prices.

Lauraceae, fossil leaf. Registration no. P 231195 (photograph by Jon Augier, copyright Museums Victoria)

Such is the electricity required for aluminium smelting that electricity prices are a major influence on its profitability; a point Alcoa used to its advantage in negotiations with government over whether it would keep its already subsidised Portland operation open following a blackout in 2016. Such an incredible amount of electricity was required by the Point Henry smelter that the Anglesea coal mine could only provide less than half of the energy needed. The remainder came from Victoria’s other brown coal reserve, the Gippsland Basin that stretches underneath the Latrobe Valley. Extensive coal mining and power station infrastructure was established in the Latrobe Valley partly to cater for the voracious hunger for electricity of Alcoa’s aluminium smelter in Portland, helping legitimate the government’s construction of the 500 km, 500 kilovolt transmission line that stretches across the bottom of Victoria, distributing coal-fired power to millions of users along the way.

The Continuous Cold Mill tower at Alcoa's North Plant in Tennessee, United States (photo by Brian Stansberry via Wikimedia Commons)

In her book Aluminum Dreams: The making of light modernity (2014), sociologist Mimi Sheller documents Alcoa’s leading role in the weaving of postwar dreams of prosperity-based peace. Distracting from the heavy, polluting, industrial processes actually involved in producing aluminium, including its energy supply chain, potent greenhouse gas emissions and red oxide ponds, aluminium dreams of light modernity draw attention to the elemental properties of the metal itself: its shininess, lustre, lightness, ductility, and resilience under stress. Aluminium’s sleek lines and versatility have underpinned its privileged place in our everyday lives and aesthetic norms. Even sustainability critiques have been met with positivity. Aluminium’s lightness is now celebrated for enabling more energy-efficient vehicles. It is also ‘endlessly recyclable’, with the process requiring just five per cent of the energy needed to produce it. In theory, this means that aluminium can be circulated virtually continuously within a circular economy, at least if recycling plants are kept open. It in no way guarantees, however, that more is not produced and that the circle does not swell ever bigger.

Aluminium production continues to grow in part because it enables as well as requires another growing industry, electricity transmission, which, regardless of energy source, is primarily responsible, along with aluminium production itself, for the synthetic perfluorocarbon molecules that warm the atmosphere thousands of times more effectively than carbon dioxide and linger in the atmosphere for thousands of years. A 1929 advertisement for Alcoa in Bloomberg Businessweek proudly proclaims aluminium’s nation-building role in electrifying the United States. ‘Aluminium is acting as the vehicle for the transmission of that most intangible of all travellers – electricity’, it declares. ‘Hundreds of thousands of miles of Aluminium Cable of every conceivable size – from the great 220,000 volt high tension lines to the small telephone wire – weaves its web of civilization across the countryside ... bringing light and sound communication and power; carrying harnessed electrical energy from the point of its generation to the point of its use.’

Colonel Paul W. Tibbets, Jr., pilot of The Enola Gay, waves from his cockpit before the takeoff, 6 August 1945 (photo from the U.S. National Archives and Records Administration via Wikimedia Commons)Another of the sectors heavily reliant on aluminium, and particularly interested in the ‘web of civilization’ it weaves, is the military. Contributing to Alcoa’s success in the early twentieth century was its core domestic relationship with the US military, helping fit out not just its electricity infrastructure and food stores but its rockets, satellites, and aircraft. Like other planes, the one that infamously dropped the atomic bomb on Hiroshima – the Enola Gay – had an aluminium alloy skin. The radioactive traces that Enola Gay’s trip left behind added to those that had been unleashed upon the world two months prior by the Trinity Bomb atomic test. Being the starting point of a radical, global-scale environmental experiment involving the detonation of more than 2,000 atomic bombs, the Trinity Bomb has been proposed as a potential marker of the commencement of a new epoch for the Earth, the Anthropocene.

The proposed Anthropocene epoch is yet to be formally endorsed. Should it be so, its significance for geologists is that it requires a rewriting of part of the official international geological record, although pre-human eras such as the Eocene will remain untouched. For Earth System scientists, the significance of the Anthropocene is even more profound. As their disciplinary name suggests, Earth System scientists imagine the Earth as a single system of interactions between the biosphere, lithosphere, hydrosphere, cryosphere, and atmosphere. From this perspective, the Anthropocene represents a major step change in planetary functioning, precipitated among other things by the simultaneous logarithmic surge in the mass dislodgement, production, and movement of matter around the planet and its dangerous accumulation in the atmosphere. The Anthropocene spells a shift from the ‘Goldilocks’ homeostatic state of the highly habitable Holocene epoch we barely registered we were in, into a different, less habitable one. Recent modelling suggests that unless the changes that are progressively unfolding abate and the Earth is restabilised through some kind of radical collective effort, we are headed for a ‘Hothouse Earth’ scenario. Being beyond anything humans have experienced, this is a future that is hard to imagine. Yet perhaps the forty-million-year-old leaves preserved in the Melbourne Museum provide clues. At the time they were growing, Earth was also a Hothouse, one uninhabited by humans. The leaves thus point to a possible temporal analogue of the future.

More tangibly, the rainforests of the Eocene provide clues as to our future because of the special treatment its lignite form has received. More than the leaves per se that caught the attention of David Christophel in the overburden of the Anglesea coal mine and, later, colleagues and I on our visit to the Melbourne Museum, the real clue as to which way the Earth’s future may unfold seems to lie in the leaves’ surrounding matrix, a dense brown matter that continues to entangle elaborate supply chains, sites, times, and dreams.