George J. Brooke describes the break in the Great Isaiah scroll.
George J. Brooke, "Isaiah in the Qumran Scrolls," The Oxford Handbook of Isaiah (New York: Oxford University Press, 2020)
On the bisection of the scroll the most detailed early observations were those William Brownlee published on the topic after having delivered a paper at the 25th International Congress of Orientalists in Moscow in 1960. Most modern readers of Isaiah are educated to think of a major division in the book belonging between chapters 39 and 40. But “the gap between chapters 33 and 34 in the Complete Isaiah Scroll, together with orthographic peculiarities of each half, point to the practice of bisecting the Book of Isaiah into two scrolls: (a) chapters 1–33 and (b) chapters 34–66.”