40d:Chasm

Chasms are a feature that appear infrequently in mountainous biomes. They are a cave system identified by not having a floor on the lowest level (which is instead marked # and described as "Chasm" when looked at).

Chasms come in two forms: standard chasms, which look something like a river system (a bottomless "Grand Canyon"), and "bottomless pits", which are like a magma pipe without the magma. Chasms are much more common on named mountains and volcanoes, along with other special features such as cave rivers. Chasms may either be open to the sky, or fully underground and not visible until breached by a miner (at which point, the entire chasm is revealed).

Chasms are not visible on the Region/World maps or the Local maps by default, but can be turned visible by setting SHOW_EMBARK_CHASM (for tributaries) and SHOW_EMBARK_PIT (for pits) to ALWAYS in init.txt. They must also be set to be shown during world generation. On the local map, standard chasms will show up as gray #s and bottomless pits as gray Os.

The presence of Extreme Cliffs (20+) on the Local Map is sometimes indicative of a chasm, though this may be coincidental.^[Verify]

Forms

Standard

The beginning of a standard chasm appears similar to the fringed tributary section of a brook sometimes seen in mountain areas, and the rest looks pretty much like the watercourse of a brook or river (though with small caves in the walls). Appears as # on the embark map if enabled.

Bottomless pit

Note: See Pit for other uses.

A bottomless pit, also called a vent chasm, has a similar appearance to a magma pipe, except it does not contain magma. Appears as ○ on the embark map if enabled.

Uses

Garbage dump

Chasming refuse refers to disposing of items marked for dumping into the chasm. This is still possible: designate a garbage dump activity zone over the chasm and an adjacent walkable tile. To dump an item, examine it with k and mark it for dumping. Standing orders can be used to automatically dump particular types of refuse. Dwarves may cancel the dump task due to creatures they can see across the chasm, even if those creatures can't reach them ^{v0.27.176.38c}

Historical note: In the 2D version, the chasm could spawn monsters, and dumping things into the chasm would provoke attacks. Dumping a sufficient amount magma in the chasm would exterminate them. This no longer occurs in the current version.

Platform-chasming

A technique of dumping by building a platform over the chasm, and then severing the platform from the wall, to permanently dispose of garbage, excess stone or nobles set on top. The severed platform will disappear into the darkness below, never to be seen again.

Resources

Often cave spiders are present near chasms, creating spider silk webs that can be collected. As the chasm exposes every layer to view they provide access to easily identified resources such as ore deposits.

Hazards

Dwarves fighting near the edges of cliffs have a propensity to dodge right off the precipice, falling to their deaths.

The chasm is also home to many types of hostile creatures, including iron men, troglodytes, giant cave swallows, antmen, giant cave spiders, ratmen, batmen, trolls and gremlins.

Adventurers Beware

Chasm creatures will spawn endlessly near chasms, leading to the death of any fortress you visit. This only applies to adventure mode. A sure formula for fun, one might add.

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