Structural Geology: Brunton: Strike and Dip: Lab скачать в хорошем качестве

Structural Geology: Brunton: Strike and Dip: Lab

How to measure strike and dip with the Brunton transit (compass). This video covers how to measure strike and dip of a planar surface in each of three situations: (1) an overhanging surface, (2) the usual case of an upright surface of moderate dip, and (3) an upright surface of very shallow dip. These demonstrations use a propped slab of rock in the laboratory/classroom. Note that some of the Brunton transit models have a raised ring (alidade mount) on the underside of the transit. This ring complicates measuring strike and dip on surfaces having a very shallow dip. A workaround is described in this video. This video employs what I refer to as the “American right-arm rule” for expressing the strike and dip of planes; looking to the strike direction, the plane dips in the direction of the observer’s right arm, i.e. clockwise from the strike direction. This is very different from the “British right-hand rule”, as it is sometimes defined. For example (from the 1st scenario), consider a plane that strikes to the northeast (or southwest) and dips to the northwest. By the right-arm rule used in this video, the strike would have to be expressed to the southwest in order to preserve the dip direction (to the northwest). Thus, a strike and dip of 234, 46 (or 234/46), expressed following the right-arm rule, is equivalent to N54E, 46NW, using a quadrant notation for strike, or 054, 46 NW, using azimuth, dip, and dip direction. Personally, I see no harm in including the dip direction with the right-arm rule. Doing so provides something of a safety net while taking notes and makes it equivalent to azimuth, dip, and dip direction. By yet another convention, that of dip and dip direction, this strike and dip (234, 46) is equivalent to 46, 324 (or 46/324). Also note that punctuation/delimiters (comma, space, slash, etc.) can vary. This video was produced during the winter of 2020-21, at the heart of COVID, as part of my effort to teach a field methods class, partially online. CHAPTERS (PARTS) 00:00 Intro 00:15 Overhanging surface 03:30 Upright surface, moderate dip 06:54 Shallow dipping surfaces