Erosion
Difficulty Advanced
Music Sunshine Serenade
Default Co-op division Free-for-all
Introduced Version 37.0
Entrances 6 Exits 6
Junctions 0 Water? Yes
Path lengths (RBS)
PathEasyMediumHard
First9.08.27.2
Second11.210.29.0
Third14.613.311.7
Fourth13.612.410.9
Fifth9.88.97.8
Sixth5.44.94.3

Erosion is an Advanced map in Bloons TD 6, introduced in version 37.0. It takes place at an ice floe which gradually melts as rounds progress. A polar bear is present on the map, which moves to stay on solid ice every time a piece melts. The polar bear does not interact with towers or Bloons.

This map's concept was designed by /u/TheWiseTroll, for the "200k Map Contest Competition" held on /r/btd6, and it was selected as a winner along with Dark Dungeons and Covered Garden.[1]

Layout

Erosion has 6 different paths, with only one of which being active at a time. On round 1, this starts with the path in the bottom-left.

At the end of round 17 and every 18 rounds after (35, 53, 71, 89), the land between the current track and the next tracks will collapse, selling all land towers on the ice and changing the path to the next lane. Pat Fusty, Ice Monkeys, Mermonkeys, Sun Temples, and True Sun Gods are not sold and transform into water towers when the land under them erodes. Additionally, any towers in range of an Arctic Wind or above's ice platforms will also not be sold. The map reaches the top-right lane and stops eroding on round 90, and the round 90+ lane is the shortest lane out of any lane in any map that gives rewards in BTD6 (only Blons has a shorter lane). Heli Pilots cannot be placed on the top-right section of this map, despite having enough space to do so (can be observed by placing a Banana Farm, which has a larger footprint and can be placed).

Boss Bloons always appear on the third path, regardless of the round number.

Strategy

Erosion is not particularly difficult outside of CHIMPS mode since towers sold by the eroding mechanic give back cash, though heroes shouldn't be placed on eroding land. However, the eroding mechanic, along with the extremely short length of the final track, makes Erosion a difficult Advanced map. Place as few towers as possible outside of the permanent platform in CHIMPS, as they don't give cash back once they sink. For the early game and mid-game, use global towers placed on the top-right or towers able to be teleported. Alternatively, Arctic Wind and its ice platforms can be used, now that itself is allowed to be placed on water.

Name Portrait Reasoning
Corvus   His Spirit can pop Bloons from anywhere, and his Spear spell is very powerful throughout the early game. At level 7, he can use Spirit Walk to move to a new lane away from collapsing ice and constantly gain mana. During the mid-game, his Spellbook can save up titanic amounts of money for a solid tower that defeats the late-game, such as Carpet of Spikes and Bloon Exclusion Zone. In the late-game, Corvus still has solid utility with Ancestral Might and Overload.
Psi   Psi's global ranged attacks and abilities make them useful starting in the early game onwards and provides a good source of support DPS that can make saving up for expensive win conditions easier.
Bloon Exclusion Zone   Bloon Exclusion Zone has a reasonable save-up because of the long length of the mid game tracks. Once afforded it easily beats the late game rounds with a source of lead popping.
Carpet of Spikes   It is powerful on this map due to the extremely short length of the round 90+ lane. The short length of that lane allows for extreme concentration of spikes that deal massive damage with every passive & active ability, easily sweeping DDT rounds, doing solid damage to ZOMG shells, and eliminating Round 100's BAD as a problem altogether. Use the 0-5-2 crosspath, as without it, most spikes will be wasted on inactive lanes, and use a MIB or Embrittlement to give it DDT popping power.
Advanced Intel   This upgrade allows Monkey Subs to adapt to lane changes by attacking within the range of other towers. It is primarily used for the early game, with Airburst Darts coupled with this upgrade contributing significantly throughout.
Arctic Wind   Arctic Wind platforms are important if wanting to salvage land towers, especially for Round 90 and above, which offers little space, and opens room for larger towers including Heli Pilot (which artificially cannot be placed on the top-right island). Additionally, Arctic Wind offers Ceramic slowdown for a decently low cost.
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The editor that added this notice elaborates: r18, r36, r54, r72, r90

In other languages

This section was last updated for: version 48.1
Language Text Notes
Arabic المحو "Erasure"
Danish Erosion
German Erosion
Spanish Erosión
Spanish (Latin America) Erosión
Finnish Eroosio
French Érosion
Italian Erosione
Japanese 腐食 "Corrosion"
Korean 침식 Same meaning as English. The Hanja form is "浸蝕".
Dutch Erosie
Norwegian Erosjon
Polish Erozja
Portuguese (Brazil) Erosão
Russian Эрозия
Swedish Erosion
Thai Erosion Untranslated.
Turkish Erozyon
Chinese (simplified) 侵蚀
Chinese (traditional) 侵蝕

References