Part of that is due to the writing system - Icelandic has an unusually wide gap between spelling and actual pronunciation (as does English). The spellings often

Part of that is due to the writing system - Icelandic has an unusually wide gap between spelling and actual pronunciation (as does English). The spellings often reflect older pronunciations, so it'd be easier for a modern Icelander to read the Eddas than to understand casual speech of their era. (Again, similar things are true of English to a less extreme degree: The Canterbury Tales are a struggle to understand, but I can plod my way through them with the aid of heavy glossing. But I doubt if I could have a conversation with a time-traveling Geoffrey Chaucer.)