ONTOLOGICAL REPRESENTATION OF RIFTS Arijit Mitra and A.K. Sinha Department of Geosciences Virginia Tech

RIFTS Rifts are fault-bounded elongate troughs, under or near which the entire thickness of the lithosphere has been reduced by extension during their formation. Rifts form in many tectonic settings such as above mantle plumes and at all stages of the Wilson Cycle.

Significance of Rifts Rifting of continents involves two principal geological processes - tectonism and magmatism, which reflect the strain-rate and temperature dependent processes of deformation and adiabatic decompression melting within the earth. Continental extension and break up are fundamental to understanding the origin of ocean basins and the mechanics of plate tectonics - all ocean basins form as a result of continental extension.

Significance of Rifts The fundamental geological processes that cause crustal extension - mantle convection, mantle plumes, opposing forces from slab pull and ridge push, and gravitational collapse. Hence, the study of rifts will enable us to determine - the original local and regional states of stress - the spatial and temporal distribution and rate of strain - the pressures and temperatures - the physical and chemical properties of rocks and fluids involved - heterogeneity of the continental lithosphere prior to rifting - the pattern of mantle flow - the extent & style of melt generation & emplacement

ONTOLOGY for RIFTS Reference: Sengor & Natal’in, 2001

RIFT-RELATED ROCKS IN THE MID-ATLANTIC TEST BED Two main phases of rifting (extension) in the Appalachians Cryogenian Magmatic Province 760 Ma failed rifting event divergent plate boundary rift without previous doming (k22) Catoctin Volcanic Province 570 Ma rifting event that led to the formation of Iapetus ocean & break-up of Rodinia Geological data from these two geological provinces are part of the VIRGINIA TECH IGNEOUS ROCK DATABASE

GLOBAL DATABASES ON EXTENSION RELATED ROCKS GEOROC NAVDAT PETDB PETROS USGS DDS 14 Geochronology Database EarthRef

Conclusion Integration of the above-mentioned databases and web-based access through high performance computing is envisioned as part of the GEON cyberinfrastructure initiative. An ontology driven integration is vital since ontologies are used as a computational pathway for answering queries.

Conclusion A spatial and temporal comparison of geological provinces improves our understanding of geological processes and provides fundamental information on the physical and chemical evolution of continents through time. Rift environments represent continental-scale processes that involve extrusion of igneous rocks, evolution of sedimentary basins, extensional/compressive tectonism to metamorphism and leave a geophysical signature. An ontological linking and integration of these multidisciplinary datasets will improve our understanding of complex dynamics of Earth systems.