[hguant]

Couple of different answers to these questions:

a) whales don't tend to go where volcanos are. Whales dive to find food, and their food sources aren't near the seabed. I think the deepest diving whale species are sperm whales, and they go after squid, which are not typically found near volcanos.

b) it's not a question of matching frequency with the whales, it's a question of noise emissions and the amount of energy you're putting into the water. Modern active sonar systems are incredibly energy intensive, and the technology to modify the waveform and limit the power of the waveform to match something biologic doesn't really exist, and would have to justify all the added complexity

c) USN and US geological survey charts are really really good, and regularly updated, to the point where "It wasn't on the charts!" is a claim met with extreme skepticism. 9 times out of 10 some sort of navigation or systemic error was involved.