Trevor, Anna and Sean are stuck inside an active volcano. Their only hope to escape is to start an eruption that will propel them out of the volcano. On his last flare, Trevor finally lights a spark between two igneous rocks in the wall to begin the eruption.
Hannah instructs the group to go down into the chasm, as it may be their only hope out of the cave. Professor Anderson is the first to climb down, and Sean follows but takes much longer, as he is frightened. During the descent, Professor Anderson notices some metamorphic rocks and tells Sean about them. He loses his balance and is put into what he initially thought was a perilous situation.
Sean trips, and his knife falls out of his pocket. He notices that the knife floats in mid-air and checks his compass to find that it isn't working, meaning there is a magnetic field in the area. He travels to the other side of a large opening using large rocks suspended in air, with many close calls during his journey.
Professor Anderson leads the group through the underground cave. He almost falls down a deep chasm as he tries to assure the group that he's good with directions. He attempts to use a flare to measure the depth of the chasm, but the magnesium rocks cause it to explode. Hannah then gives him a glowstick, and he uses that to determine that the chasm is about 200 feet deep.