MAGIC MT - Uplift of the Appalachians

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Non-technical summaryThe eastern edge of the North American continent is located far from currently active boundaries of tectonic plates, and is thus often considered relatively "quiet" in plate tectonic terms. However, the eastern margin of North America has experienced a long and rich plate tectonic history, most recently being involved in the break-up of North America and Europe and the formation of the Atlantic Ocean. That break-up involved multiple important geologic processes, including magmatism, stretching of the continent, and uplift that is responsible for the formation of the Appalachian Mountains.Although most of this activity finished long ago, there is evidence to suggest the Appalachians are even now being partially supported by flow of the mantle beneath the mountains. We are using electric and magnetic fields of the earth recorded at the surface to image the structure of the continent and the properties of the underlying convecting mantle, in order to better understand the processes that control modern day topography and those involved in continental break-up, or rifting. The project partly supports the education of a PhD student as well as training of highly skilled technical staff, and the experiment uses equipment manufactured by Cape Abilities, a non-profit company on Cape Cod that finds work for people with disabilities.Technical summaryWe are carrying out fieldwork to collect magnetotelluric (MT) data in a profile of about 28 stations across the Appalachians, from Ohio to Virginia. The MT method measures naturally occurring electric and magnetic fields at the surface of the earth, and uses this information to image structure to depths of several hundred km below the surface. The method measures the ability of the earth to conduct electrical current, a property that is sensitive to temperature as well as to the presence of fluids such as water or magma. We can construct a cross sectional image of the deep structure along the entire length of the profile. The survey is coincident with an ongoing seismic experiment, and we are working with the principal investigators of that project to carry out a coordinated joint interpretation of results constraining lithospheric thickness, hydration state of the mantle, and the presence of any partial melt associated with mantle upwelling.