Hydrological Investigation at El Morro National Monument: Final Report

van Dam,, Remke; Hendrickx, Jan

The sandstone bluffs at El Morro National Monument (ELMO-NM) house culturally important petroglyphs and inscriptions of American Indians, early Spanish settlers, and Anglo Americans. The relatively soft sandstone that allowed the inscriptions to be made also makes the rock susceptible to erosion. As a result, many inscriptions suffer from erosion processes that lead to deterioration. The sandstone cliff at El Morro National Monument is extremely complex due to variation in topography, stratigraphic layering and temperature regime, due to the presence of numerous faults and cracks, and due to differences in exposure to sunlight and wind. Earlier studies have outlined the prominent role that water plays in several processes that possibly cause the deterioration of the rock inscriptions: impact by rain drops on the bluff surface; freeze-thaw cycles with water in the pores or in cracks, chemical dissolution of pore cement and grains transported by water that may cause dissolution. The National Park Service (NPS) has asked the research group of Dr. Hendrickx at New Mexico Tech (NMT) to study the nature of the hydrologic processes at ELMO-NM. The recommendations made by Pranger (2002) form the direct cause for the involvement of NMT in this project.