Mapping subtle structures with light detection and ranging (LIDAR): flow units and phreatomagmatic rootless cones in the North Mountain Basalt, Nova Scotia

Light detection and ranging (LIDAR) is an emerging technology to generate high-resolution digital elevation models (DEMs). Subtle topographical differences among three flow units of the Jurassic North Mountain Basalt, eastern Canada, are visible on a LIDAR-derived DEM. The boundaries were verified by field mapping and allow a simple projection of the contact planes through the terrain model to provide a three-dimensional visualization of the flow units. Several ring structures in the lower flow unit, distinguishable only in the LIDAR data, are interpreted to be the remnants of rootless phreatomagmatic cones. Glacial erosion has since excavated the highly fractured cone material, leaving the more resistant dike and quenched melt to form protruding ring structures. The ability to detect subtle variations in topography using LIDAR may identify previously undetected landscape elements.