How geology and topography influenced the Battle of Valverde (February 21, 1862)
— Daniel J. Koning

Like all land battles, the geologic and topographic features present at the Battle of Valverde, a Civil War battle 40 km (25 mi) south of Socorro, influenced the battle narrative. Particularly important features were: (1) two different-aged basalt flows capping Mesa del Contadero and an extensive terrace surface, (2) loose eolian and alluvial sand southeast of Mesa del Contadero, and (3) river channels on the floodplain north of Mesa del Contadero. Mesa del Contadero, which owed its existence to the basalt that capped it, is a conspicuous landform that controlled the geometry of the Rio Grande floodplain and was a topographic obstacle that both partly shielded the Confederates and also partly blocked their path. The cliffs and ledges of the lower Jornada basalts to the south of the mesa, which cap a 12–15 m (40–50 ft) tall terrace, and the fact that the Union army controlled the one piece of non-basalt covered, sandy ground that allowed access to the river, prevented the Confederate army from obtaining water and resulted in them being severely dehydrated on the day of battle. This dehydration was compounded by the intense physical effort needed to pull wagons and artillery through loose, eolian and alluvial sand southeast of Mesa del Contadero. The intense need for water spurred them in a “do or die” charge toward Captain Alexander McRae’s battery, whose successful capture resulted in a battlefield victory. The active Rio Grande at the time flowed south immediately north of Mesa del Contadero, and 650 m (700 yd) to the east was a dry (abandoned) river channel. The active channel offered refuge for the Union army from Confederate bullets, but impeded reinforcements to defend McRae’s battery. The eastern, dried-up river channel offered essential protection for the Confederate troops and allowed them to muster “under cover” toward McRae’s battery before their desperate charge. Moreover, the desire to enfilade and deprive the Confederates of this protection motivated Colonel Canby to send more troops from the middle of his line to the advancing southern flank, so that when the Confederates charged toward McRae’s battery there were less Union men at hand to stop it.