A work in progress

This piece doesn't have a working title, and this is only the 1st part.

Shawn, Tonya, and Alex arrived at their destination, the Galapagos Islands, early in the morning. They left their things at Alex’s cousin’s house, and then headed for the lush forests of the islands. Alex’s fiancé, Ruth, had arrived the day before and had already set up a base camp. The four friends had been looking forward to the trip for more than a year. Eagerly they trekked up thin trails, spying rare and beautiful creatures at every turn. On they marched, going deeper into the heart of wilderness, and higher up the side of power.
"Hey Shawn!" Alex called from the rear, "Is it just me, or is the ground sloping upwards?
"We’re going up the side of a volcano. What did you expect, the ground going downward? Shawn replied, chuckling.
"Step by step, we attempt to scale a volcano. We, the equivalent of ants on a mound, dare to step on ground that has the power to blast us off the face of the earth." Intoned Tonya, with a look of awe, as she gazed up at the volcano, still far ahead.
"The drama queen, how oft' she does scream, of death and destruction, and all kinds of corruption, now stop your screechin’, and stop your preachin'!" The two boys bellowed in unison.
Tonya removed her mask of awe and replaced it with one of anger. After a few moments she broke into laughter and continued up the spindly trail. The boys, having no more antics to dispose of, simply shrugged their shoulders, and followed Tonya.
After an hour of easy hiking, the threesome left the trail. But as soon as they pushed through a few feet of foliage, the ground beneath them crumbled away. At first, they all thought that they were slipping down a steep embankment, however, it soon became clear that the ground was collapsing. Dirt, rocks, and plants came thundering down around them as they slipped farther and farther away from the surface. Tonya, Shawn, then Alex thudded heavily, yet soundlessly, amid the chaos. Rocks and dirt piled onto them for a few seconds, and then all was still. Alex, being the top most, picked himself up gingerly, wary of broken bones. He checked himself for injury, found only minor cuts and scrapes, and then began to help the Tonya. Shawn, no longer weighed down by the other two, gazed up at the hole that marked their passage into the earth. The bright blue sky pierced through the darkness that now surrounded them.
"What on earth just happened." said Tonya, genuinely perturbed.
"Umm, I think the ground just caved in, and we are in a pit." Alex answered.
"I don't think we are in a pit, Alex. I think we were above a cavern that had a thin roof. When our combined weight was over a particularly weak spot, it could no longer support us. Let’s just hope that this cavern is not a product of the volcano."