Time capsules from the depths of the Earth: how “detective” Alessia Borghini deciphers ancient climate secrets
Let’s imagine the harsh, wind-swept landscape of Norway or the ancient, forested hills of Poland’s Sowie Mountains. It is there, with a geological hammer in hand, that Dr. Alessia Borghini works. The sharp sound of striking rock is not just the sound of crushed stone; it is the first step on a journey deep into time. Dr. Borghini, a metamorphic petrologist, does not see a mere dead object in a rock chip. For her, it is a book, written in the language of minerals and pressure, telling a story from hundreds of millions of years ago.
Dr. Borghini is like a detective at the scene of a crime that happened in the unimaginably distant past. Her work involves collecting evidence – rocks that witnessed the birth and death of continents. The central mystery she seeks to solve is one of the most important for our civilization: how does our planet regulate its climate on a geological timescale? And what can rocks that formed between 420 and 100 million years ago tell us about Earth’s future in the face of today’s challenges?
The answers to these questions lie in the microscopic world. Dr. Borghini studies tiny “time capsules” – melt inclusions trapped in minerals. These microscopic bubbles are like fossilized samples of the atmosphere and chemistry from deep within the Earth, from times when great mountain ranges were forming. By analyzing them, Dr. Borghini and her colleagues piece together the history of our planet’s deep climate engine. This is a process of fundamental importance for understanding current environmental changes and the challenges we face. Every stone she picks up is not just a fragment of the Earth’s crust; it is an artifact that has traveled both in space – from depths of tens of kilometers to the surface – and in time, from the distant past to the present.
Key witnesses in Dr. Borghini’s investigation are metamorphic rocks. Their name comes from the Greek word metamorphosis, meaning transformation. And that is their essence: these are rocks that formed from already existing rocks – sedimentary, igneous, and even other metamorphic – subjected to extreme conditions. Imagine a piece of coal that, under unimaginable pressure and temperature deep underground, transforms into a diamond. This is a perfect analogy for the process of metamorphism. These rocks are subjected to temperatures exceeding 150-200°C and pressures of 100 megapascals or more, causing profound changes in their physical structure and chemical composition.
Where do such extreme conditions come from? The theory of plate tectonics provides the answer. The Earth’s surface is not a uniform crust, but a mosaic of gigantic lithospheric plates that are constantly moving, drifting over the Earth’s plastic mantle. When two such plates collide, one of the most dramatic geological processes occurs – subduction. Typically, a denser oceanic plate is pushed or pulled under a lighter continental plate, submerging deep into the Earth’s mantle. It is in this collision zone, tens of kilometers below the surface, that rocks are crushed, heated, and transformed, becoming metamorphic rocks.
This process is inextricably linked to mountain building, or orogenesis. When continental plates collide, the marine sediments that separated them are folded and uplifted, forming mighty mountain ranges. This means that mountains are not static elements of the landscape. They are dynamic scars of planetary collisions, and the rocks from which they are built are eyewitnesses to these cataclysms. The Sowie Mountains, where Dr. Borghini conducts some of her research, are precisely the remnants of such an ancient mountain range, built largely of gneisses – a type of metamorphic rock. Thanks to geological processes that brought these rocks to the surface, places like the Sowie Mountains become an accessible laboratory, allowing us to study processes that normally occur hidden, deep beneath our feet.
After collecting samples in the field, Dr. Borghini’s work moves from the macroscale of continents to a world invisible to the naked eye. Her main tool becomes the optical microscope, and the object of study – melt inclusions. It is these that Dr. Borghini calls “tiny time capsules,” and this analogy perfectly captures their nature. These microscopic traps store a perfect, chemical “screenshot” of the conditions prevailing in the subduction zone at the moment of mineral formation.
Dr. Borghini’s work perfectly illustrates this fundamental principle of science: progress often involves re-evaluating what was considered “noise” and discovering that it is, in fact, a crucial “signal.”
Dr. Borghini’s research focuses on rocks from hundreds of millions of years ago, but its implications are thoroughly contemporary. As she herself emphasizes: “A better understanding of how these cycles worked in the past allows us to better understand how the Earth evolved to its present state.” The movement of water, carbon, nitrogen and other elements caused by tectonic shifts (known as the deep volatile cycle) is a key element of our planet’s long-term “carbon budget.” The release of vast amounts of volatiles into the atmosphere – whether as a result of massive volcanic eruptions in the geological past, or as a result of human industrial activity today – has dramatic consequences for the climate. By understanding the natural rate and scale of carbon circulation in the geological cycle, we can fully appreciate how unprecedented current anthropogenic emissions are. Disrupting this delicate balance, honed over eons, leads to consequences we are already experiencing: a rapid increase in global temperatures, increasingly frequent and severe droughts, fires, and extreme weather events.
Dr. Alessia Borghini, originally from Italy, is carrying out her project in Poland as part of the prestigious Polonez Bis scholarship. Her experiences perfectly illustrate what modern science looks like: it is a global undertaking, based on cooperation and the exchange of ideas across borders.
Her work at the host institution in Krakow has been, as she says, “a very positive experience.” She emphasizes the support from the team, openness to scientific discussions, and a friendly atmosphere. Importantly, she did not notice any cultural barriers or differences in work culture compared to institutions where she had worked before. Her mentor is accustomed to working with international scientists, and his research group consists of people from various countries and at different stages of their careers. This international and open environment has made her work in Poland extremely pleasant and productive.