"It's not, a lot of effects are slower, but better sorcerers are faster."

"Hmm! Do you happen to know how far down we'd have to drill to either hit magma or be sure there's none under us?"

"Uh... maybe a few miles? I've never really dug."

"Well, let's go ten miles down and if that doesn't do it we can ask the Bus," she says, turning a knob that causes the latter to extend an enormous drill from where her front radiator grill usually is.

"Okay."

There is not magma ten miles down.

The process of finding that out involves the bus diving through the rock like a fish, drill a-spin, with the gravity in the control room shifting as it tips over so they're still standing on the floor. Ms Frizzle discusses the rock they're tunneling through as she goes.

It's pretty samey rock.

And that is in itself weird and interesting! She already knew this rock didn't cool in the aftermath of star formation, but this is such a clear illustration of it! But eventually they stop drilling and start scanning increasingly large areas for a magma zone.

There is none to be found at this time.

"Fascinating! Promise, the magma pockets aren't as old as your world and they haven't formed yet. Let's do a binary search to find out how and when!"

"A binary search?"

Time to explain binary search! And now that they're on the Bus, she can pull up a chalkboard and draw diagrams! You start with a pair of bounds, in this case a point in time when you know there is magma in a certain location and a point when you know there isn't, and check halfway between them. That tells you whether the magma appeared in the first half of the time window or the second half. Then you repeat the process on your new half-sized time window, and keep repeating until you have something small enough to search exhaustively.

"...I guess that will work on when even if it can't help with where."

"For the where, I was hoping you'd know the location of one in your time. Or at least a general area we could similarly look around in."

"I don't know where to find magma that's just hanging out underground. I can name some volcanoes."

"We should definitely go to a volcano! Perhaps we can figure out how they formed in the absence of planetary geology."

"Probably you don't want to start with the one that erupts mercury, then. How about Ashrock?"

"Ashrock it is, though I definitely want to see the volcano that erupts mercury at some point!" She starts pulling dashboard levers.

"Can you aim for when it's erupting?"

"Certainly!" Up comes a volcano on the viewing screen, belching smoke and just starting to pour out lava. "That looks nice and energetic. Come on Bus, do your stuff!" 

The Bus responds with "Bee-beep!" and reality starts getting weird out the windows again.

"Why does it look like that?"

"The Bus travels by pinching off a little pocket of space-time and reattaching it to reality at large at a different point. Sort of like scooping a cup of water out of a pond and pouring it into a different one, and what we're seeing is like the ripples in the water."

"Huh. Why does this have an appearance?"

Promise can have an explanation of high-energy physics which this margin is too small to contain! The gist is that sloshing spacetime around like that tends to make any photons in the area go all over the place, like looking into fun-house mirrors if fun-house mirrors had a lot more options. Also, they are now hovering in the ash cloud above the volcano's crater.

"We'll probably have a better view of the volcano from outside the cloud."