SLAUGHTER IN THE ROCKS AND OTHER GEOLOGICAL ASPECTS OF THE BATTLE OF PEA RIDGE

The March 6–8, 1862 Battle of Pea Ridge, one of the most important Civil War battles of the Trans-Mississippi, followed the August 1861 Battle of Wilson’s Creek as well as a number of smaller battles in the Arkansas/Missouri theatre of war. The battle revolved around the eponymous Pea Ridge (also known as Big Mountain or Elkhorn Mountain), a crescent-shaped outlier on the Springfield Plateau topped by a thick sandstone layer within the Fayetteville shale. Within what is now the Pea Ridge National Military Park, the Springfield Plateau is relatively flat south and west of Pea Ridge. The battle had a number of geographically and geologically-related aspects. These included: ambush preparations along extensive (but ultimately unused) entrenchments along stream bluffs in a more highly dissected area south of what is now the main part of the National Military Park; high ground that couldn’t be successfully defended; and Devil’s Den like topography on a rocky ridge replete with rockslide and topple blocks. Large disarticulated blocks of the Wedington Sandstone along the ridge provided a seemingly safe and easily defendable redoubt, but the setting instead acted to amplify the effects of well-placed, explosive artillery rounds, resulting in “slaughter in the rocks.” The battle included fast movements, topography that variously masked or exposed these troop movements, use of mobile equipment including the mountain howitzer, and remarkable recoveries and reversals in fortune.