BURIED EXPLOSION EXPERIMENTS PROVIDE INSIGHT INTO EJECTA FACIES DISTRIBUTIONS AND MORPHOLOGY OF SINGLE AND MULTIPLE EXPLOSION SYSTEMS

Buried explosion experiments provide an opportunity to investigate the processes and deposits from discrete subsurface explosions. Single and multiple subsurface explosions using chemical explosives produced meter-sized craters and deposits with radial and circumferential variations in thickness, sorting, and componentry. Single blast experiment deposits have similarities to impact crater structures and ejecta, while multi-blast experiments have greater similarity to maar-diatreme volcanoes and deposits from discrete explosions through established conduits and hydrothermal systems. These experiments revealed the sensitivity of ejecta cloud shape and deposit distribution to the depth an explosion occurs below the surface and the energy of the explosion (scaled depth = depth of burial/cube root of the energy). This distribution can be discussed in terms of proximal and medial / distal deposition zones. The proximal deposits form a constructional steep-sided ring that extends no more than two-times the crater radius away from center. The medial and distal ejecta form a blanket that transitions from continuous, to discontinuous ejecta, and finally isolated clasts. The abundance of proximal ejecta relative to the medial and distal ejecta is sensitive to scaled depth and the number of explosions in the system. Single explosion systems through flat ground have increasing volume contributions of proximal ejecta as scaled depth increases (20-90% vol.), however, explosions through pre-existing craters are dominated by proximal ejecta (90% vol.) at all but optimal scaled depth conditions (40-70% vol.). Additionally, the number, symmetry, and length of radial features in the discontinuous ejecta deposits are influenced by the number and relative location of explosions within multi-blast systems. The discontinuous ejecta features are the result of instabilities in the ejecta cloud and are emplaced by outward expanding ballistic curtains.