[Strategerist]

Well, you've got history during the existence of humans, and then you have "recorded history" which is history since the beginning of writing.

The wording of the article probably should have been "recorded history"...Tambora is the largest volcanic eruption during that time period. It's not the largest eruption in human history.

[ThanhPhero]

There is no unrecorded history. History is the record of the past, not conjecture about the past and not even the reality of the past except as it was written down. It is records. Recorded history is redundant.