There are not multiple chains.
Those involuntary forks you are talking about happen when 2 miners find a block about the same time. But in the next block the situation is solved
Fork, Accidental Fork
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This definition comes from the technical glossary.
Definition
When two or more blocks have the same block height, forking the block chain. Typically occurs when two or more miners find blocks at nearly the same time. Can also happen as part of an attack.
https://bitcoin.org/en/glossary/forkYou can track them here
https://www.blockchain.com/charts/n-orphaned-blocks