Control of Jointing by Topography

Chapman, Carleton; National Park Service, Acadia National Park

From Introduction, 'detailed study of a large homogeneous body of massive granite shows a high degree of interdependence for jointing, sheeting, and topography.' 'The concept that jointing in rock masses exerts a pronounced influence upon topography is old and well established. The idea that topography may in turn influence joint development, however, is not commonly realized and is almost entirely restricted to the phenomenon of sheeting. Detailed study of a large homogeneous body of massive granite shows a high degree of interdependence for jointing, sheeting, and topography. The theory is advanced that most joints are perhaps the surficial expression of directions of weakness within the massive granite. The existence of numerous directions of potential cracking in the granite leads to the supposition that favorable directions for rock expansion will determine in large part which potential joint sets may become opened. Trend, frequency, and spacing of joints as determined in the field, therefore, are influenced to a large extent by detailed configuration of the topography. Sliding of granite layers on inclined sheeting planes provides the necessary expansion for consequent opening of two steep joint sets, one more or less parallel and the other perpendicular to slope strike. Thus sheeting and topography play an important role in the selective development of open joints from the numerous potential sets in the massive rock.' /STUDY LOCATIONS:/ /MOUNT DESERT ISLAND/

Control of Jointing by Topography

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