No one was. It was too soon after breakfast. Instead, Rick took the opportunity to ask questions.
"I can understand the general principle of what we're doing, but can you tell us exactly what happens?"
"Sure. When the dynamite charge goes off, it sends shock waves through the earth in all directions. Whenever a shock wave strikes something of different density, its direction and velocity change. For instance, if there is denser rock a few hundred feet down, that will cause a change of both velocity and direction. With me so far?"
"I think so," Scotty said. "The denser the stuff the wave strikes, the faster it moves. Like sound waves. I mean, sound moves faster in water than in air, and faster in a steel rail than in water. Is it the same?"
"Just about," Zircon agreed. "The shock waves radiate away from us, through the earth, and eventually reach the recorders on the other side of the mountain. You can see what happens, I think. Waves will arrive at different times, depending on the path they took and the kind of material they went through."
Rick nodded. "So if there's molten rock, or magma somewhere in the way, the shock wave that goes through it will slow down and arrive at the recorder later?"
"That's it. The tracings we get can be analyzed to give us a kind of cross-sectional look at the mountain. You see, we know how fast the waves travel through different kinds of earth structure. Also, we will know the point of the explosion and the location of the recorder for each shot. Which reminds me. We'd better get out the equipment and locate ourselves precisely."
"How?" Rick asked. "What will we use for landmarks?"
"The top of the mountain, for one, and if you'll look carefully to a point slightly south of east between those two banana palms, you'll see the top of the control tower at the airport."
Rick shook his head. "Good thing you're with us. I completely forgot to watch for landmarks."