After my first experiences with the pristine, ancient rocks in Greenland, geological field work in tropical northern Australia was a shock. The rocks were either completely overgrown with thorny vines or weathered to a deep red soil, or both.
My first foray into the geology of northern Australia was in October – not the time of year to be doing field work. But I had just arrived and I was eager. It was a poor decision. The temperature rarely ducked below thirty degrees Celsius in the evenings, and it crept over thirty-seven during the day. An enthusiastic ten minutes in the midday sun on the first day left me with heat exhaustion, slumped in the truck with the air conditioner blasting freezing air into my face, brain pounding with the strain. Quickly, I learned to plan my field work around shade, water, and – where possible – air conditioning.
From a distance, the tropical north was a stunningly beautiful place. I recall a day of helicopter-supported work. We flew out into the dense wilderness, over snaking brown rivers fringed by thick, dark green vegetation, over pavements of orange sandstone, waterfalls diving into crystalline blue pools, and I pressed my forehead against the glass, wishing myself into this stunning, pristine, inaccessible landscape. Then the helicopter descended. At close range, the vegetation was thick and thorny, the rivers dark with shadows. And when the rotors wound to a halt, the wind brushed past the trees and swept in with a humidity that that left me breathless and gulping for air. I spent the day literally fighting the bush. My field assistant and I took turns to hack away at the head-height vines with a machete. When there was nowhere to sit and rest, I could just lean into the undergrowth and it would hold my weight. Even when I found rocks to look at, I could barely summon the energy to pull out my notebook. I drank litres of water and didn’t urinate.
At the end of the day, we had arranged to meet our colleague, who was walking alone, atop a low hill with a clearing just big enough for the helicopter to land. My field assistant and I arrived early and each lay in a patch of longed for shade, trying not to breathe too much, unable to converse. Half an hour later, our colleague came crashing through the bush like an injured beast. Bursting from the trees, he cried, “Give me water!” and fell to his knees clasping the bottle I held out to him, pouring it into his mouth faster than he could swallow.
On another day, walking down a dry river bed, I searched for rock outcrops that could sometimes be found in the sandy banks. These rocks, I suspected, were over two and half billion years old and I needed a sample to test my hypothesis. But when I touched the rocks they crumbled in my hands and red powder drifted away in the breeze. I longed for the sharp ping of my hammer against those fresh Greenlandic rocks, the youngest of them two and a half billion years old, not the dull thud of metal against rocks now long expired.
I paused, thinking of one particular rock outcrop, somewhere in the Nuuk fjord region in Greenland, that remained fixed in my mind. My heart beat a little faster at the thought of it. Two black rocks. That’s all it was. Both beautifully preserved, fresh and clean, completely unweathered, untouched by time’s ancient hands. The youngest was a basalt dyke just over two billion years old. But the darker rock that it cut through – also a basalt dyke – was about three and a half billion years old, formed more than three quarters of the age of the Earth ago. There they sat, each inconceivably ancient, the sharp contact between them representing one and half billion years between the formation of the first and the second. The first had formed far below the ocean floor, when no land masses yet rose above the toxic oceans that drowned the Earth, when a pale sun looked down from a dark sky. The second had cut through the first when lands of bare rock stood above the waves, only single-celled life squirming in the silent seas. And yet, a further two billion years on, here I sat, a rarified ape who knew a little about geology, feeling the cold of these perfectly preserved rocks against her palms, drinking in the thought of the unimaginable eons of time stretching back into their inconceivably distant past, these pieces ancient Earth transported through time.
With that thought, as the tropical dust of long dead rocks filtered through my fingers, I heaved my heavy rucksack onto my shoulders and continued down the hot, dusty river bed.
