lava falls fans
under the for what its worth department. my questions about lava falls drop and current speed finally went far enough upriver to reach the source or sources:
richard quartaroli, special collections librarian at cline library (for their colorado river archives) and past gcrg president.
susan w. kiefer, dept of geology, university of illinois and the maker of the hydraulic map of lava falls (among others).
robert webb, usgs in tucson, author of many papers about the rapids in the grand.
concensus is that the 37 foot drop of lava is for the drop through lava and the rapids below it. it has a 24 foot drop from mile 179-180 and a total of 37 feet stretching from mile 179.3 to mile 181.3, a distance of almost 2 miles.
the real drop of lava falls ranges, depending upon flow is from 12-15 feet over the course of the rapid, about 100 yards or so, again depending on flow.
the misinformation began with some early surveys. this is from quartaroli:
As part of my research into printed river guides, rapid rating systems,
drops in rapids, &c., the first time I found that 37' drop for Lava Falls
appeared in print was in the Hamblin and Rigby geology field guides, c.
1969. John Cross II took them down The River, as he also did with
geologist Troy Pewe. There are several non-geological things wrong in the guide, such as calling the "Ross Wheeler" "Old Ironsides." I asked Crossin 1994 on the Old Timers Trip if he remembers telling Hamblin/Rigby 37' drop in Lava. He couldn't remember, but he said he started out at Hatch River Expeditions before his dad founded Cross Tours, so maybe he got itfrom a Hatch boatman and passed it along to H/R.
IIn 1869, Jack Sumner with Powell estimated the drop at 12'
At any rate, once the 37 foot drop appeared in print it was repeated over and over again. It appeared in the Stevens 1983 guide which further perpetuated the legend.
so there you have it. as far as the legendary speed of lava....the 100 mph the smithsonian film talked about is absurd. the rapid, according to webb is way less then 20mph except for where it pours over the ledge hole.
ahhhh the joys of research.