That depends on how you define "Blockchain". My definition of "blockchain" is a distributed ledger in a entirely trustless p2p network. To which PoW is the mos

That depends on how you define "Blockchain". My definition of "blockchain" is a distributed ledger in a entirely trustless p2p network. To which PoW is the most widely deployed mechanism in use to secure against the double spend problem. Pow being a mechanism that remains un-superseded inspite of significant efforts to do so. All this making PoW hardly orthogonal. Of course this definition of a "blockchain" can be loosened. One of two tweaks and suddenly we need to label prosaic everyday items such as a git repos as "blockchains". At which point it becomes difficult to even have conversation about "blockchains" since our industry has yet to bring to bear a sufficient amount of focus to even define the term with any sort of useful precision.