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To unravel the mysteries surrounding the present structure and past evolution of the continent requires the application of the diverse methods by which geoscientists study the Earth. The great success of LITHOPROBE has been its coordinated, multidisciplinary approach. By bringing together geologists, geochemists, geophysicists, and focussing their knowledge and energy on major geotectonic problems, the scientific study of those problems is enhanced far beyond the level of individual contributions.

Some of the techniques used are very briefly described below:


  • Geological Mapping
    - Mapping the geology exposed on the Earth's surface is the foundation upon which all LITHOPROBE transects are based.
  • Structural Geology
    - Structural studies involve determining the geometry and style of folding that has affected the rocks. In addition, the geometry and nature of the faults that cut the Earth are established. These observations permit some inference of the direction of paleostresses.
  • Igneous and Metamorphic Petrology
    - The study of how rocks form and evolve when exposed to high pressures and temperatures deep in the Earth.
  • Stratigraphy and Sedimentology
    - The study of how sediments and structures form near the Earth's surface and evolve over time.


  • Seismic Reflection
    - A technique used to image boundaries between different rock types and structures. Energy, usually generated mechanically using large "vibroseis trucks", is sent into the Earth. When the waves pass a boundary between different materials, some of the energy is reflected back to the surface. These near-vertical reflections are used to construct a high-resolution (e.g., 100 metres) map of lithospheric structures. Linked with surface geological maps, these reflection profiles spearhead the detailed multidisciplinary interpretations.
    [Click here for more information]
  • Seismic Refraction
    - Refraction surveys image subsurface structure at a much lower resolution (e.g., 1 kilometre) than typical reflection surveys. However, refraction surveys provide detailed velocity information that is essential for interpreting reflection data and for determining the composition and state of the lithosphere. Refraction surveys also record reflection data over a large range of angles, providing another suite of data to interpret interface structure and composition. Refraction surveys utilize large explosive sources to generate the energy that must propagate upwards of 600 km along a profile. LITHOPROBE reflection and refraction surveys image lithospheric structure to depths greater than 70 km.
    [See the WWW pages describing the recent SNORE97 experiment]
  • Gravity and Magnetics Studies
    - Measurements of the spatial variation of gravity can be used to constrain the density of structures in the Earth's crust. Interpretations of density distributions are often carried out in conjunction with seismic refraction/reflection studies since density and seismic velocity provide a mutual constraint on structural modeling.
    - The magnetic field measured at or above the Earth's surface is dependent upon the magnetization and iron content of the rocks making up the crust. Magnetic anomaly data, derived after subtraction of time variations and broad scale regional fields can be a powerful interpretive tool for establishing the geometry and nature of subsurface rock formations.
  • Electromagnetic Studies
    - Electromagnetic (EM) studies investigate the electrical conductivity of the subsurface. Conductivity is a physical property that is independent of velocity and density. Instead, it is extremely sensitive to composition, texture and fluid content within and between rocks. Highly conductive materials include saline water in interconnected pores/fractures, graphite films, and silicate partial melts.
  • Heat Flow and Geothermal Studies
    - The Earth's interior heat drives tectonic processes. Temperature dependent rheological properties control zones of strength and weakness in the crust and thus depths at which tectonic motions take place. In addition, heat is ultimately responsible for the formation of mineral deposits and the maturation of hydrocarbons in sedimentary basins. Therefore, measuring the temperature gradient in the crust and determining the thermal conductivity of rocks can provide useful information for interpreting Earth structure and history.
  • Paleomagnetism
    - The techniques of paleomagnetism are based on measuring the directions of magnetization "frozen" into rock formations at their time of origin or at subsequent times when they have been reheated or metamorphosed. By making careful corrections for the present attitude of a rock formation (how it has been folded or tilted) and comparing these directions with the known magnetic field at the time of their magnetization, it is possible to determine the original latitude of the rock. This information plays an important role in unravelling the movements through geological time of terranes and continents (ie. continental "drift").
  • Physical Properties
    - All geophysical observations relate in some way to the physical properties of rocks -- seismic to compressional and shear velocities, gravity to density, magnetic to magnetic susceptibility, electromagnetic to porosity and electrical conductivity, heat flow to thermal conductivity and heat production, and paleomagnetism to various types of magnetization. Laboratory studies of such properties are a key to correct interpretation of field data.


The processes involved in the formation and modification of the Earth's lithosphere (igneous processes, erosion and formation of sediments, tectonic-metamorphic processes) tend to have unique chemical signatures. Thus, geochemistry adds another important sector of information used to form a more complete model of the processes of crustal generation and evolution.

Geochronometry is a special branch of geochemistry, related to isotope physics, that involves determining the time of formation of rocks, minerals and fossils. Many different techniques and isotope combinations are used depending on the specific target age and material. However, most utilize the principle that radioactive isotopes present at the "birth" of a mineral will decay at a certain fixed rate. Measurement of relative abundances of the "parent" and "daughter" isotopes can determine the age of the rocks. Dating of surface exposures of rocks is required to connect the observed rocks with the geophysically-determined geometry and domains at depth.

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