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Description
Planetary bodies in the inner Solar System are also called terrestrial planetary bodies and include Mercury, Venus, Earth, Mars and the Moon. When heated rock melts at a depth of several kilometers below the surface of these planetary bodies, magma is produced. This magma then rises and is emplaced at shallow depth in the planetary crust, or it erupts at the surface. During shallow emplacement, magma creates space for itself and it deforms the surrounding rocks. As a result, the planetary surface is deformed as well. Both linear and dome-shaped surface features have been found at the surface of terrestrial planetary bodies. Dome-shaped features include a series of impact craters on the Moon that possess uplifted and fractured crater floors. Numerical models can be used instead to estimate magma intrusion geometry, orientation, depth and volume. Most existing numerical models of magma emplacement assume that the host rock behaves elastically. Geological observations on Earth have shown, however, that the rock properties and fractures cause that rock to behave non-elastically as well. This project will use an innovative approach to numerically model the emplacement of magma in fractured rocks using a two-dimensional Discrete Element Method (DEM). Host rock samples will be collected around solidified and exposed magma intrusions in South-West Poland. Fracture networks in the host rocks will be mapped digitally using state-of-the-art photogrammetry techniques. The model results will be compared to the topography and fracture networks mapped on the Moon by using satellite images. The proposed multidisciplinary approach will allow to produce new complex models of how shallow magma emplacement deforms planetary crust. This way, this project will improve the interpretation of surface features on terrestrial planetary bodies caused by magma, as well as improve models of magma intrusion used to reduce volcanic hazards on Earth.
Summary of project results
Terrestrial planetary bodies in our Solar System that display signs of past volcanic activity include Earth, Mars, the Moon, and Venus and Mercury. When heated rock melts at depth below the surface of these bodies, magma is produced. This magma ascends through the crust and is either emplaced and solidified at a shallow depth of a few kilometres below the surface, or it erupts at the surface and builds volcanoes. During shallow emplacement, the magma creates space for itself by displacing and deforming the surrounding rocks. This process translates into deformation of the planetary surface, which can be observed through images collected by spacecrafts.
Monitoring seismicity and ground deformation at active volcanic systems on Earth has revealed that dome-shaped surface uplift features can be formed by magma intrusions that spread horizontally and inflate upwards. No active volcanism has been observed on the Moon and Mars, but dome-shaped uplift features at their surface have been interpreted as magma-induced deformation. These features include impact craters that possess uplifted and fractured crater floors. Geological observations at these features are – for the foreseeable future – impossible, and therefore analytical and numerical modeling instead helps gaining insight into the emplacement dynamics and architecture of the volcanic and igneous plumbing systems below the surface.
Most existing numerical models of magma emplacement oversimplify the mechanical response of the host rocks to the intrusion of magma. On Earth, however, geologists have found that rocks around magma intrusions are often deformed and fractured in a much more complex way. Up to now the impact of ignoring that complex deformation on existing model results was poorly understood. New, more realistic models of magma propagation are necessary to assess the uncertainty on the existing models to improve the accuracy of volcano eruption forecasts on Earth and our understanding of past volcanism on the planets and moons that surround us.
From 2021 until 2023, the research team of the DeMo-Planet project, led by P.I. Dr. Sam Poppe, implemented a new model application to numerically simulate complex magma-induced deformation. The project used a multimethod approach including numerical modelling, photogrammetry, geological observations, rock strength testing, and comparison with remote observations of planetary surfaces. This was done by working with colleagues from Ireland, France, Norway and the U.S.A.
First, the research team implemented and tested a new numerical code in an existing, two-dimensional (2D) Discrete Element Method (DEM) software. The new code simulates how a magma injection displaces and fractures rocks. The model either simulated the inflation of an existing magma body with a flat base and a domed roof (a ‘laccolith’) at the immobile model base, the injection of new magma into that laccolith, or the injection of magma at a depth within the model at a location where the host rock completely surrounds the magma body.
Second, the team verified and calibrated the numerical model by using geological observations from Earth. Commercial quarries in Lower-Silesia, Poland, provide spectacular exposures of 200-250 million-years old trachyandesite magmatic rocks and their overlying rocks. We collected picture series of the outcrops with an Uncrewed Aerial System (a ‘drone’) and used them to calculate virtual 3D models of the geological outcrops using photogrammetry software. Observations of fracture networks and rock deformation were mapped in the field and on the virtual outcrops. Geological samples were collected from representative rocks surrounding the magmatic intrusions. The samples´ mechanical strength was measured in laboratory tests at the University of Strasbourg.
The rock´s petrography was characterized using microscopy techniques at the University of Wrocław. Different methods to implement the geological observations from the Polish earth analogue site in the numerical simulations were then tested. Finally, the team compared those numerical simulations of magma emplacement at the Polish trachyandesite intrusions with simulations on the Moon and Mars under lower gravity compared to Earth.
The multidisciplinary DeMo-Planet research showed that the different strengths of rocks and different gravity on the Moon and Mars lead to differences in the ground deformation patterns there compared to those on Earth. The results can now be used to better interpret deformation features of the planetary surface caused by magma emplacement, and to better understand volcanic hazards on Earth and past volcanism on other terrestrial planetary bodies in our Solar System.
The scientific results were published in a scientific paper (Morand et al., 2024, Journal of Geophysical Research : Solid Earth) preceded by a review article (Poppe et al., 2022, Bulletin in Volcanology); minimum three scientific manuscripts are in preparation for submission to peer-reviewed scientific journals in 2024. Numerical model data are published in an open-access data set (Morand et al., 2023, Zenodo.org). The scientific results were presented at scientific meetings and at departmental seminars, increasing the academic visibility. An invitation to the P.I. to present the project´s research results in a solicited talk at the 2023 General Assembly of the European Geoscience Union in Vienna, Austria, underscores the project´s impact on the scientific debate about volcano deformation modelling.
The communication strategy encompassed a combination of successful online and in-person dissemination. Several scientific seminars are available online (+305 views), and a short YouTube movie for a wide audience (+113 views since 05/03/2024). The project´s outcomes were highlighted on the project´s facebook page (32 followers), through the X-account of the P.I. @SamPVolcano (1424 followers), and on the project´s webpage. A research summary for a wide audience was published in English and Polish by the leading science outreach platform Scientia.Global. A press message accompanied the publication of the first paper, which led to news articles on National Geographic Polska online (500 000 – 1 000 000 views) and the website “Science in Poland”, and a filmed interview for a short news item about the project outcome on Telexpress Info on television channel TVP (+200 000 viewers daily). The P.I. was also an invited speaker about planetary volcanism on the Silesian Science Festival in 2022 (+35 000 participants) and at primary school PSP Milanówek, Poland (60 students). As a final outcome, the project´s performance led to the permanent employment as specialist researcher of the P.I. at the host institution.