Originally posted by Soma:

When you hit something like a tree or rock, with your axe or pick I think your "discoverable by enemies" radius is much larger. So for abominations be sure to bang on stuff as you run around to assure being able to attract them from the farthest away possible.

Quick answer, make noise

Noise is exactly right; creatures "hear" much better than they "see". Hitting a tree can be "heard" from 100 meters away, with the player as the source of the "sound", even after they move away... it dissipates at a rate of 4m per second.

Assuming you don't mind taking on absolutely everything in the swamp, the easiest method of finding an abomination is probably to wander around the swamp, hitting a nearby tree with your axe every 10-15 seconds to keep a large "noise" radius.

https://valheim.fandom.com/wiki/Creature_senses