So-called "Rootless cones" are caused by explosions of lava with ground ice under the flow.
 The ice melts and turns into a vapor that expands in an explosion that produces a cone or ring.
  Features like these are found in Iceland, when lavas cover water-saturated substrates.
So-called "Rootless cones" are caused by explosions of lava with ground ice under the flow.  The ice melts and turns into a vapor that expands in an explosion that produces a cone or ring.   Features like these are found in Iceland, when lavas cover water-saturated substrates.
Elysium quadrangle