Shield volcano are cave-like volcanic straights formed by the hardening of overlaying lava. These structures help further the propagation of lava, as the walls of the tube insulates the lava within. Lava tubes can account for a large portion of shield volcano activity; for example, an estimated 58% of the lava forming Kīlauea comes from lava tubes. In some shield volcano eruptions, basaltic lava pours out of a long fissure instead of a central vent, and shrouds the countryside with a long band of volcanic material in the form of a broad plateau. Plateaus of this type exist in Iceland, Washington, Oregon,
Jackson Volcano limestone. The structure was noticed by Hopkins in 1917 and a successful gas well was drilled in 1930, but the field was nearly exhausted by 1939. Jackson Volcano ash within the Eutaw Formation produces oil in the Tinsley Oil Field, where oil was first discovered in the Woodruff Sandstone (Selma Chalk), an eroded sand from Jackson. Jackson Volcano Jackson Volcano is an extinct volcano beneath the city of Jackson, Mississippi, under the Mississippi Coliseum. The uplifted terrain around the volcano forms the Jackson Dome, an area of dense rock clearly noticeable in local gravity measurements. E.W. Hilgard published his theory