LITHOPROBE Methodology

LITHOPROBE is a scientific project of international stature and the largest Earth science research project ever undertaken in Canada. It comprises a network of centers of excellence involving collaborative, multidisciplinary investigations of the nature and evolution of Earth's lithosphere beneath the Canadian landmass and surrounding oceans; it is acclaimed by some experts as the best Earth science project of its kind in the world.

LITHOPROBE derives from "probing the lithosphere". The present lithosphere consists of a global mosaic of plates all moving relative to one another. The collision, separation and side-swipe motion of these plates and their predecessors and the recycling of Earth material into new plates over billions of years has amalgamated, sorted, compressed and modified Earth's lithosphere to form the present continents. How this has occurred is a fundamental question of Earth-science research and one that LITHOPROBE addresses throughout its scientific program. Knowledge of the composition and geometry of this continental amalgam in three dimensions, and of its evolution during the fourth dimension - time, is vital to the exploration for buried mineral and hydrocarbon resources, and for understanding Earthquake and volcanic hazards that occur at the surface.

Trans-Canada LITHOPROBE Map
LITHOPROBE is a coordinated yet highly decentralized research program. Its principal scientific and operational components are built around a series of transects or study areas, each of which is focussed on carefully selected geological features of the North American continent that represent globally significant geotectonic processes. Each transect (in the above figure; click on figure for description and enlargement) includes an integrated set of projects that address fundamental problems concerning the structure and evolution of the lithosphere and are carried out by a multidisciplinary transect team headed by a Transect Leader(s). Together, the ten transects represent a concerted effort to develop an enhanced understanding of how the North American continent has evolved to form the present Canadian landmass.

The science of LITHOPROBE is spearheaded by the seismic reflection method because this is the geophysical technique that produces the best images of boundaries between rock units and of structures in the subsurface. In its application, the seismic reflection method is highly complex, involving a skilled acquisition crew with millions of dollars of equipment whether on land or at sea. On land, LITHOPROBE has been using large truck-mounted mechanical vibrators as sources (the "Vibroseis" method) because they are logistically appropriate and environmentally safe for the hard-rock areas surveyed. In a typical regional survey, 240 groups of geophone sensors are spaced at 50 m intervals over a 12 km length. Sensor outputs are recorded on a truck-mounted computer system. High resolution surveys, for which the geological targets are in the uppermost crust and the 240 groups are spaced at smaller intervals (10 to 20 m) over 2 to 5 km, have been undertaken with the participation and collaboration of industry and provincial government agencies. A description of the seismic reflection method and the subsequent data processing can be seen at the LITHOPROBE Atlas Home Page.

To unravel the mysteries surrounding the present structure and past evolution of the continent requires a coordinated, multidisciplinary approach. In addition to seismic reflection surveys, which spearhead the LITHOPROBE research, other methods applied include:

Questions or comments? (Litho@geosci.lan.mcgill.ca)