1.
Near Ranger Creek before the turnoff to Crystal Peak ski area.
Gray materials below is probably Osceola lahar, about 5500 yrs old.
Very clay rich with no layering and wide range of particle sizes.
Above red oxidized horizon is post-Osceola glacial outburst flood
deposits
and/or regular flood deposits. Sandy bouldery with weak layering.
2. Closeup of same. Water gushing out of oxidized horizon.
3. Downstream away from the volcano the lahar deposit can look
like a garden variety sandy pebbly river deposit. The subtle
upward curving
dish structures are produced when water is expelled from the lahar
while compacting down after coming to rest. NOT typical of garden
variety river deposits.
4. Near Mud Mountain dam outside of Eunumclaw in a roadcut.
The brown blobs are ripped up pieces of sand and gravel. They
are NOT solid, they are completely loose. BUT they were carried
downstream many miles in the gray lahar WITHOUT being totally
disrupted. The lahar flows downhill as a pasty plug, NOT as a
turbulent
liquid (like water). And so little mixing of the lahar.
5. Near Eunamclaw, out on the flat plain, the lahar has thinned
down to just a layer a meter thick or so, surrounded by soils and
sands above and below. Could be hard to recognize as a lahar.
This thin layer is said to be "distal", far from the source.
6. Brian Atwater (right) lays out the goodies on the
Eunamclaw plain, built from Mt. Rainier lahars. Brian
is showing vertical samples of deposits from the Seattle
area, a weird kind of flat core that cements the goop together
for sampling. Fantastic. Small layers of lahar are visible.
