Here is how the fire was started in Equinelantis: The Lost Kingdom.
It was the middle of the night before dawn, When some strange figures came to the camp and scoped the place.
???: Is the close is clear?
???: Yes.
???: Good. Now then, Let's find the majesty's journal.
Just then, Yuna woke up as they fled off.
Princess Yuna: (lights up her horn for light as she tip-toes past Cookie)
Jebidiah Allardyce "Cookie" Farnsworth: (talking in his sleep)
Princess Yuna then stands next to a rock, But the light from her horn starts to attract fireflies coming from the chandelier-shaped rock on the ceiling and started to buzz around her face.
Princess Yuna: Shoo, Fly! Shoo! Go away!
As one firefly lands on her cape, It caught on fire!
Princess Yuna: Holy Moonshine! (takes it off quickly)
Yuna then saw a lot more fireflies coming her way. As she ran off without warning, She sound her alarm.
Princess Yuna: Fire! Fire in the Camp! FIRE!!!
Princess Luna: (yawns) It's still too early.
Princess Celestia: (as she and Luna got out of the tent) Yuna, Back to bed.
But when they saw the camp on fire, Everyone got out trying to put out the fire.
Cruz Ramirez: Get some water on that fire!
But no matter how many buckets of water were thrown, The fire just kepts spreading due to the fireflies.
Princess Celestia: This fire's getting too intense! We need to evacuate!
Zapp Brannigan: The Princess is right! Get across that bridge and into those caves! Move it, Move it, Move it! On the double!
Soon all vehicles started heading for the bridge as fast as possible.
Milo Thatch: Dipper, Over here!
Kida Nedakah: Mabel, Give me your hand!
Dipper Pines: (jumps onto the back of the truck)
Marbel Pines: (grabs Kida's hand and is pulled onboard just as one truck explodes)
Just as the group were almost on the other side of the bridge, The oil truck exploded which caused the chandelier-shaped rock to fall and then the bridge began to crack as then it started to break loose, as Mole's driller then starts sliding back.
Gaetan Moliére: (trying to stop the driller from sliding back) No, No! No, No, No, No, No!
But then the driller bumps onto the other vehicles, causing them to slide back too as the bridge's broken end hits the ground sending all vehicles sliding down a steep hill and crashing into each other.
Cleveland Brown: No, No, No, No, No, No!
Lightning McQueen: Aaaaah!!
Mater: Whoaaaa!!!!
Cruz Ramirez: WHA!!!
(crash)
When it was dark, No one could see anything until Scoorge lit a match.
Scrooge McDuck: Alright, If anyone else is not dead, Just give a holler.
Everyone else starts moaning and groaning.
Jebidiah Allardyce "Cookie" Farnsworth: Dang blasted bugs done bit me on my sit-upon, Someone gonna have to suck out that poison. No body jump out at once.
Mater: (turns on his one headlight) Them dadgum lightnin' bugs done did a bad number upon our resources, Where are we anyway?
Princess Skyla: I'm not sure, But at least everyone is alive and well.
Zapp Brannigan: Audrey, What's the damage report?
Audrey Ramirez: (shining a flashlight on the vehicles) Not as bad as it could've been. We've totaled rigs: 2 and 7. But the Digger looks like it will still run. Lucky for us we landed in something soft. (rubs her back)
Gaetan Moliére: (zooms in on the ground) Plumith ash. (picks up the obect with a claw and takes an even closer look) We are standing in the base of a dormant volcano.
Judy Hopps: (loads a flare gun and fires it up)
The flare flies up really high.
Judy Hopps: It just keeps going.
Vincenzo Santorini: Maybe that's our ticket out of here.
But then the flare hits the top
Judy Hopps: Or not.
Peter Griffin: Why'd it just stop like that?
Gaetan Moliére: The magma has solidified in the bowals of the volcano, Effectively blocking the exit.
Patrick Star: I don't get it.
Joshua Sweet: Whoa, Back up. Are you sayin' this whole volcano can blow at any time?
Gaetan Moliére: No, No, No, No! That would take an explosive force of great magnitude.
Gyro Gearloose: That would make a bigger explosive.
Nick Wilde: Well, There has to be some way to get out of this thing! I'm not too crazy of standing in a volcano even if it isn't active!
Scrooge McDuck: Yuna, What do you think? (notice she's not here) Yuna? Yuna?
Princess Luna: Oh no, Where's Yuna!?
Princess Celestia: We have to find her, She could be anywhere.
As the flashlights were on, They begin their search for Yuna.