Chasms

Chasms are deep tunnels in corrupted parts of a world, and can be loosely identified as holes in the ground lined with a thick layer of corrupt stone. Generally, they reach depths around where the Underground or Cavern layers begin.

Depending on the world, there can be two different kinds of corrupt biome, The Corruption and The Crimson.

Corruption Chasms
Chasms in the Corruption are pretty much what you would imagine a chasm to be: a long vertical tunnel which drops straight down into a dark abyss usually ending with a Shadow Orb at the bottom. The walls in these chasms are made of Ebonstone, with Ebonstone Wall in the background. Although sometimes they may hit a dead-end at the bottom, they often reach a long, horizontal tunnel which spans most of the corrupted biome. This tunnel houses a large quantity of Demon Altars, and has Shadow Orbs buried some distance beneath. Usually, these chasms will continue down further, so it is strongly recommended that one exercises caution when trying to reach this tunnel.

Crimson Chasms
The Crimson features chasms of a different sort, and are made up of Crimstone beginning at a horizontal entrance. Whereas the chasms of the Corruption are linear, Crimson chasms are rounded and often change direction multiple times before reaching a large open area which branch out further at the bottom. Unlike the chasms in the Corruption, Crimson Altars (the Crimson equivalent of Demon Altars) can be found concentrated at a single layer on the decent into the chasm. Demon Hearts (the equivalent of Shadow Orbs) are found at the ends of each of the "fingers" that form at the bottom of the opening, trapped behind several blocks thick of Crimstone. While it is easier to navigate in these tunnels, it should not be taken for granted that the openings in the Crimson chasms are very large, and the walls out are jagged and often difficult to climb. Be sure you are prepared with equipment enough to escape before jumping in.

Tips

 * Corruption chasms:
 * Players without the ability to mine Ebonstone and who have not yet obtained a climbing aid like Grappling Hooks will want to avoid falling into chasms. Some chasms can be very difficult or impossible to climb out of by merely jumping between ledges.
 * It's best to use a weapon that has a long reach when going down chasms to knock out Eater of Souls that usually cluster on the other side of the Chasm.
 * If you have the chance, it's best to cover off the chasm to avoid falling into it at a later time.
 * Crimson chasms:
 * Along with being impossible to fall into,Crimson chasms are easy to navigate, and don't require climbing or jumping gear to escape.
 * Crimson chasms are somewhat harder to find, as they may be buried. The entrance is vary distinctive, however, and can be spotted by identifying a large mass of Crimstone
 * Rooms with Demon Hearts are frequently located under water (as seen in the image above). In such cases the player may need a water-breating item, such as Gills Potion, to reach them.