Day 7: A chance to step back

On our last day of field work, we drove to a high point on the side of the Roseau Valley to look at the entire valley and get a larger perspective on the work we've been doing.  The north and south sides of the valley are flanked with rolling hills, while the valley floor is extremely wide and flat.  We are exploring the idea that the rolling hills, made of fractured volcanic rock, contain water within their fractures.  Furthermore, we are exploring the idea that the same structures that create the rolling hills might also exist below the valley floor, but covered by a thick floodplain of clay and silt.  Our resistivity measurements on the valley floor over the past week are helping us to find the volcanic structures below the valley and determine whether they have fractures or pores that contain water. 

Conducting a hilltop sounding, with the Roseau Valley in the background.

We took one short sounding on the top of the hill which produced some nice resistivity data.  We have inverted this data to get an estimate of the resistivity of hill material.  If similar resistivities exist below the valley floor, it may suggest the underground roots of the same hills that make up the valley walls. 

Resistivity data going down to 35m depth on the hilltop.