by The Earth’s surface is the ‘living skin’ of our planet – it connects the physical, chemical and biological systems. Over geological time, landscapes change as this surface develops, regulating the carbon cycle and nutrient circulation as rivers transport sediment into the oceans.
All these interactions have far-reaching effects on ecosystems and biodiversity – the many living things that inhabit our planet.
As such, reconstructing how Earth’s landscape has evolved over millions of years is a fundamental step towards understanding the changing shape of our planet, and the interplay between things like climate and tectonics. It can also give us clues about the development of biodiversity.
In collaboration with researchers in France (French National Center for Scientific Research, ENS Paris University, University of Grenoble and University of Lyon), our team at the University of Sydney has now published a detailed geological model of the Earth’s surface changes in the prestigious journal Science.
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Ours is the first dynamical model – a computer simulation – of the past 100 million years with high resolution down to 10 kilometers (6.2 miles).
In unprecedented detail, it reveals how the Earth’s surface has changed over time, and how that has affected the way sediment moves around and settles.
Divided into million-year frames, our model is based on a framework that incorporates plate tectonic and climatic forces with surface processes such as earthquakes, weathering, shifting rivers, and more.
Three years in the making
The project started about three years ago when we began the development of a new global model of landscape development, capable of simulating millions of years of change.
We also found ways to automatically add other information to our framework, such as paleogeography—the history of the Earth’s landscape.
For this new study, our framework used state-of-the-art plate tectonic reconstructions and simulations of past climates on a global scale.
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Our advanced computer simulations used Australia’s National Computational Infrastructure, running on hundreds of computer processors. Each simulation took several days, building a complete picture to reconstruct the last 100 million years of Earth’s surface evolution.
All this computing power has resulted in global high-resolution maps showing the highs and lows of the Earth’s landscape (elevation), as well as the flows of water and sediment.
All of these fit well with existing geological observations. For example, we combined data from current river sediment and water flows, drainage basin areas, seismic surveys and long-term local and global erosion trends.
Our main results are available as time-based global maps at five-million-year intervals from the Open Science Framework.
Water and sediment flow through space and time
One of the Earth’s basic surface processes is erosion, a slow process in which materials such as soil and rock are worn away and carried away by wind or water. This results in sediment flows.
Erosion plays an important role in the Earth’s carbon cycle – the never-ending global circulation of one of life’s essential building blocks, carbon.
Examining the way sediment flows have changed through space and time is crucial to our understanding of how the Earth’s climate has varied in the past.
We found that our model reproduces the key elements of Earth’s sediment transport, from catchment dynamics showing river networks over time to the slow changes in large-scale sediment basins.
From our results, we also found several inconsistencies between existing observations of rock layers (layers), and predictions of such layers. This shows that our model can be useful for testing and refining reconstructions of past landscapes.
Our simulated past landscapes are fully integrated with the various processes at play, especially the hydrological system – the movement of water – which provides a more robust and detailed view of the Earth’s surface.
Our study reveals more details about the role that the ever-evolving Earth’s surface has played in the movement of sediments from mountaintops to ocean basins, ultimately regulating the carbon cycle and Earth’s climate fluctuations through deep time.
When we explore these results in tandem with the geologic record, we will be able to answer long-standing questions about various important features of the Earth system—including the way our planet cycles nutrients and gave rise to life as we know it.
Tristan Salles, Senior Lecturer, University of Sydney
This article is republished from The Conversation under a Creative Commons license. Read the original article.
