Earth Dynamics Research at RSES

Introduction to Earth Dynamics

The Earth's crust and lithosphere (in fact, the planet as a whole) is both dynamic and evolving. Earth dynamics is about the evolution of the architecture of our planet's lithosphere and mantle: how it deforms, when it deforms, how fast and why; from individual grains to mountain belts to entire continents. Some of us go from rocks to mass spectrometers; others use computers to analyze geophysical datasets in 3D-time, or to predict the results of the physical processes acting on and within the planet.

Research topics

	Subduction zone processes	The recycling of elements through convergent plate boundaries strongly influences the chemical differentiation of Earth. It is widely accepted that hydrous fluid sourced from dehydrating subducting crust promotes melting in the mantle wedge and the formation of arc magmas.
	Earth Resources	Australia is wonderfully rich in mineral resources (Fe, coal, gas, gold, etc) that are so vital to our economy, and at the same time worryingly scarce in other resources vital to our welfare (groundwater). The projects outlined below use field observations, experimental data and modelling to determine the physical and chemical processes ultimately controlling the formation and management of the resources available to our nation.
	Virtual Earth	The Virtual Earth is a 3D digital rendition of our planet, including the interpreted geometry of subducted slabs from modern and ancient subduction zones around the world. The slabs are modelled as triangulated meshes that will be made available as open source data (through AuScope) accessible to the general geological community as point-set and DXF formats. This allows geologists and geophysicists, for example, to examine slab geometry (in 3D virtual reality) and to test new concepts about Earth processes.
	Mantle Dynamics	Internal motions in the mantle are fundamental drivers of crustal geology and the evolution of the planet.  The mantle flows by convection, which is driven by sinking tectonic plates and rising mantle plumes.  Research topics include detailed numerical and laboratory modelling of mantle convection, including subduction and plumes, and the thermal and geochemical evolution of the mantle.  The work complements work in geochronology and geochemistry, seismology, tectonics and subduction zones.  It is also relevant to hazards from earthquakes and tsunamis.
	Dating Deformation and the Nature of Orogenesis	To understand the tectonic evolution of the Earth we need to know when events occur, and how fast they take place. The 40 Ar/ 39 Ar system is unique in that it allows both geochronology and geospeedometry, as well as direct dating of fabrics, where the effect of different deformational events can be preserved in a single rock, or grain. Regional metamorphism as well as short-lived metamorphic events can be distinguished and dated using SHRIMP. Microstructural analysis with 40 Ar/ 39 Ar geochronology offers a powerful and complementary tool to determine the temporal evolution of mountain belts.
	Experimental Mantle Studies	Once subducted oceanic crustal material has been processed in the subduction zone environment (see the preceding paragraph), it is likely subducted into the deeper, convecting mantle as eclogite, the high-pressure form of basalt. Eventually this material may be incorporated into the mantle source regions of some erupted magmas. For example the geochemistry of some oceanic island basalts has been interpreted to suggest that discrete bodies of eclogite or pyroxenite in peridotite-dominated mantle, partially melted at high pressures and contributed to the lavas that erupted at the surface.
	Tectonic Evolution of the Alpine-Himalayan Mountain Chain	The Alpine-Himalayan mountain chain was caused by the closure of the Tethyan Ocean, and extends from the European Alps, through the Aegean Sea and the Anatolides, to the Himalayan ranges of northern India and southern China, through SE Asia, Papua New Guinea, out into the SW Pacific to New Caledonia and New Zealand. Research undertaken aims to understand the evolution of the mountain chain from its beginning into the future, and ranges from reconstruction of its 3D evolution, to detailed specification of its time history at a small number of control points.
	Tectonic Reconstruction using Pplates	Pplates is open source software developed at RSES as part of the ACcESS MNRF. Pplates uses 2D deformable meshes to move plates and associated data in a 3D Earth, allowing effects such as extension, shortening and tearing to be taken into account. Researchers use this reconstruction technology to introduce basic geodynamics (e.g. isostasy) into tectonic reconstruction.