b'Environmental geophysics the valleys and the well-conducting Tertiary clays, to hitherto unachievable depths and accuracy, and to a large degree also discern between the sand and clays formations within the valleys. The geophysical contribution to hydrogeological investigations had just taken a leap forward, and we had substantially improved the knowledge base necessary to implement a sustainable abstraction practice in the densely populated area of Aarhus. Furthermore, our activities contributed to a better understanding of the formation processes behind the structure of the present geology.A leap forwardAn important aspect of the success was the much-improved productivity: two people could make 16 - 20 soundings per day. We soon learned that you had to stay 150 - 250 m away from cables above or below ground and from closed electricalFigure 1.One of the first maps of the elevation to the top of the conductive unit that correlates with the fences to avoid cultural coupling to man- depth of the palaeo-valley - produced from a dense set of TEM soundings in the Beder Valley, south of Aarhus.made good conductors. Soundings were placed with an average distance betweenin many different geological locationscould place the receiver box on one, the them of ~200 m, meaning that a couplein Denmark, and an almost explosivetransmitter on another, and the receiver of square kilometres could be covered ingrowth in its application followed. A newcoil on a third one. Sometimes, in the one day. With a reasonable effort, it wasgeophysical era in Denmark had begun. absence of properly placed tussocks, now possible to cover large areas with awe would hang the receiver coil in the dense mesh of soundings and therebybranches of a small bush. All the wires provide reliable information about theExcerpts from The Strangewent from one unit into the water to subsurface. Adventures of a Geophysicist appear out of the water at the other box! The first investigation that unequivocallySome of the most memorable fieldThe data were just perfect! And we did demonstrated the potential of thedays with the Protem 47 instrument infind the depth to the salt water in the method and showed the way for futurewhich I have been involved took placelimestone under the island which was the investigations was the mapping of theon the island of Amager, just south ofpurpose of the efforts.Beder valley, south of Aarhus. Figure 1Copenhagen. The resund Bridge (Yes, shows the depth to the bottom of theDuring the same investigations, we tried buried valley and for all of the peoplethat one! The one from the TV series:to make soundings in a football stadium, involved in these early activities, it hasThe Bridge!) and the connecting newbut that was not a good idea. The many acquired an iconic status. train tracks were in the planning phase.wires for the light towers buried around Together with people from the companythe green field completely drowned out During the same period we conductedRambll we carried the instrumentsthe data in cultural coupling. And we a major investigation on the island ofacross a low-lying, inundated part of themade soundings in a cemetery, where Rm in the North Sea, close to the westisland being very careful to keep ourthe - fortunately few - visitors gave us coast of Jutland. We made two transectssocks dry and not step into the deepercurious looks while we rolled the wires across the island that clearly showedholes. The most debilitating conditionsout and in again along the footpaths the depth to the saltwater, informationfor electromagnetic measurementsbetween the graves and did our best to of major importance in relation to ais water - water and electrical currentbe invisible. This is where your gothic sustainable administration of the limitedsimply dont go together wellbut wefantasies can come alive, but as far as I fresh-water supply of the island. Withindid succeed in making some soundings.know, we did not manage to wake the a very short time, word got around, andWe had to find the few tussocks stickingdead the transient method was applied toout of the water that were big enough many and varied hydrogeophysical issuesand forming the right pattern so that weTo be continuedAPRIL 2022 PREVIEW 32'