Answer: PACIFIC PLATE
Written by Idontknow, kt3, and dalryaug
There's a lot of (intended) redundancy in the solution to this puzzle, but the intended solution is to first try to talk to the hiker on the left branch of the trial. This can only happen if you initially go left. If you go right, Dippy will be sad you missed the hiker once you loop back around to that part of the trail. The hiker tells you to try to visit every “location” once, which refers to the locations at the top of every page. There's actually only one way to do this; despite being able to loop around either left or right, the hiker only appears when you go left, and the hiker is a “location”. Taking the first and last letters of the locations spells, respectively, WEATHERCHANGESEVERYSTEP and FOUNDLETTERSDEPENDONSKY.
Some of the pages also feature somewhat conspicuous descriptions of the weather at the corresponding location. These always fall into the categories of sunny, cloudy, or rainy. These seem to change quickly between pages. In fact, every time you click a link, the weather cycles between those three states (it just isn't always noted).
At each of our caching locations, the weather is described. You're told the letters we find depend on the conditions of the sky. The emoji next to the 3 nine-letter word blanks in the brochure indicate which weather conditions correspond to which blanks. It's actually impossible to get all three geocaching sites to have the same weather conditions while just going forward, so you'll have to go back a few steps and stare at the lake (or other indefinitely-repeatable actions) and then go geocaching again to get all the corresponding letters. You're directly told in what order the letters you find go in and these lead to filling in the final riddle with “What would a GEOLOGIST call a piece of PEACEABLE TABLEWARE?”
Looking up synonyms for PEACEABLE includes PACIFIC and a PLATE is a piece of TABLEWARE, so the answer is just PACIFIC PLATE (something a GEOLOGIST might study).