Today we passed through the confluence of the Mississippi and Ohio rivers. Again, no whirlpool, but definitely impressive. The expanse of water was so great it was as though we were on a huge lake…with velocity.

Steffen started to get a little concerned with the compressor that produces the pressurized air for the pneumatic sound device. On our last survey in 2008, the compressor broke down and set us back two days while another was driven to our remote location on the river from Texas. The oil filter on the compressor, which is the same one from before, started to capture small, shiny fillings, which suggests wearing on the internal mechanics. We started contingency planning, shipping special oil from Texas and talking with the folks there about the situation—they need to be prepared to send or bring another compressor to us just in case.

Aside from the compressor, data collection went well. We are approaching an outcrop location on the Kentucky side where the river is seemingly cutting into the bank. The cliffs look to be nearly 100 ft high. Tomorrow we will make a run to the outcrop with the students in the runner boat to determine what the geology exposed in the cliff face tells us about the subsurface geology we are passing over on the Strong.

Outcrops are important in a seismic survey just as deep wells are also important because they will be used to match a reflector in the seismic data profile to a geologic unit. This way we can follow the reflector across the profile and identify if faulting of that layer exists.