Close up of erosion of explosive deposit three months after the eru...

Close view of a gully eroded into new volcanic deposits within 3 months of the eruption. The underlying soil layer, topped with pre-eruption vegetation and roots, prevented running water from eroding into even thicker tephra deposits erupted by the volcano hundreds of years ago. In many locations, however, these older deposits were also carried away by surface runoff during intense rainstorms and transported tens of kilometers downstream.