 |
Figure 16. Eruption sequence of an Eocene diatreme following the hydrovolcanic model. A, Eruption commences when an intrusion reaches shallow depths and encounters a rich source of ground water; B, the breccia pipe propagates downward, creating a cone of depression of the water table, while a tuff ring forms around the central crater and the walls of the pipe collapse downward; C, material collapses into the pipe, allowing rocks from higher in the stratigraphic sequence to fall to lower levels, while forming some crude layering. Debris flows away from the crater walls to form volcaniclastic layering. |