A volcano is an extreme terrain in any sense of the word. Ancient people thought volcanoes to be the work of gods, while astronomer Johannes Kepler thought volcanoes to be a duct for the world's tears. The most notable of these geological marvels is Hoenn's own Mt. Chimney.
Mt. Chimney is commonly called a 'dormant' volcano. In reality, most do not use this classification. It is difficult to determine whether a volcano is active, extinct or dormant. A great deal of Mt. Chimney's magma flow has been diverted, leading to the formation of numerous natural hot springs. These hot springs can be luxurious, but can be dangerous to the unwary. Certain hot springs can reach boiling temperatures. Due to water being a natural solvent and the high temperature, minerals dissolve very easily in hot springs. These can be beneficial or harmful. If you're not sure if a spring is safe, it's best not to get inside.
Mt. Chimney is known for its volcanic ash. The composition of ash is usually classified by the content of SiO2(silica) present in the ash. Pure silica, that hasn't bonded to anything, can cause health problems like silicosis. Volcanic ash with a content below 58% is unlikely to contain 'free' or non-bonded silica. Mt. Chimey's volcanic ash has is 45% silica. While this is fortunate, volcanic ash can still pose a problem. Volcanic ash can still irritate the mucus membranes and lungs if breathed in. Cover your mouth and eyes when working in areas with a lot of ash.
Volcanic eruptions(as well as volcanic vents, lahars and lava flows) release a lot of gases into the air. Most of this gas is water vapor, but other gases include carbon dioxide, sulfur dioxide, hydrochloric acid, hydrogen flouride, hydrogen sulfide, carbon monoxide, hydrogen gas, ammonia, methane and silicone hexaflouride. Some of these(CO in particular) are toxic in large quantities. Others can escape into the atmosphere and bond with water molecules, forming acid rain. This acid rain can be damaging to manmade structures, rocks, metal and plant life. Flouride and chloride can irritate skin and contaminate water, and can damage clothing. If lava is actively flowing, one should stay far away from the volcano.
Despite the harsh conditions, organisms can live quite well inside a volcano. Micro-organisms have been known to live comfortably in the heat, and a variety of Pokemon use the volcano as their home, food source or nesting ground.
Slugma and Magcargo are made from magma or lava, depending on their position. (When magma is underground, it is called magma. When it emerges from the earth, it is lava.) If they were to stop moving, or venture too far from their volcanic homes, they would cool down and harden. It is for this reason that these Pokemon remain near volcanoes, to keep their bodies hot.
Koffing and Wheezing inhabit volcanic regions because they are attracted to the foul smells of volcanic gases. Methane and sulfur compounds create a rather pungent odor, which Koffing inhale readily. These Pokemon can prove useful to clean up otherwise toxic gases from a recent eruption.
Young Skarmory have weaker skin than their adult counterparts, making them much more prone to predators. Skarmory seek out difficult-to-reach mountain peaks where they can lay their eggs. Skarmory nests are made of rough material, usually brambles, sticks and occasionally sharp rocks. The acid rain produced by volcanoes is harsh and can harm Skarmory, so if the Skarmory suddenly leave a region, there may be an impending eruption.
Machop sometimes venture to the lower peaks and craggy bases of mountains and volcanoes. The rocks are perfect for lifting and training muscle. Like monks and sages, these fighters prefer training in solitude, which is readily offered in an imposing mountain. Machop avoid the highest peaks of volcanoes out of self-preservation instincts, although they will climb normal mountains quite readily.
Grimer, like Koffing, are naturally attracted to the foul odor of volcanic gases. It is currently unknown what benefits, if any, Grimer gain from this volcanic trek.
Torkoal need coal and rock material to fuel their internal fire. The rocks found near and in a volcano are great for this purpose, as they regularly undergo similar treatment by the volcano itself. While Mt. Chimney is(thankfully) not rich in coal, it is rich in rocks that can be easily melted down by Torkoal.
Numel are resistant to the heat of a volcano and feed on the hardy plants that grow near the base. A Numel's natural obliviousness keeps it safe from the harsh environment and are often employed by people to carry heavy loads in the region.
Spoink must bounce constantly, making a volcano an excellent spot for them to live. A spoink can generate quite a bit of kinetic energy for its heart through bouncing off the peaks of a mountain.
While a volcano is by no means a vacation spot, this connection to the subterranean world of plate tectonics is much more than the barren wasteland it appears to be.