Juvenile clast-rich layer. J2 is the second scoria-rich layer and is separated from Jl by a lithic rich layer, LI and a surge layer, SI. The thickness of J2 ranges from 7 cm at site 20 to a thickness of 86 cm at site 15. J2, which contains approximately equal proportions of dense juveniles, vesicular scoria, and lithics, exhibits wavy bedding and minor pinching and swelling within the overall layer, and can be divided into three approximate subdivisions (J2a, J2b, and J2c). J2a is a black and oxidized scoria dominated (~ 60%) layer with slight reverse grading and dense juveniles. J2b is a fine grained layer marked by a greater abundance of lithics (~ 40%) than J2a. J2c is a scoria-rich layer that was not identified at all field locations. J2 was not subdivided at the type section because the layer boundaries were not well developed at this site.
Physical volcanology of a sub-plinian and phreatomagmatic eruption at Okmok Volcano, Alaska: implications for explosive mafic volcanism