John L. Sorenson writes that the destruction in 3 Nephi did not fundamentally change Book of Mormon geography.
John L. Sorenson, An Ancient American Setting for the Book of Mormon (Salt Lake City and Provo, UT: Deseret Book and FARMS, 1985), 45–46
What About the Great Catastrophe?
The location of Cumorah is not the only question that will have come to the alert reader's mind. What if the physical conditions changed so much from ancient to modern times that the former locations no longer can be found? We learn from the Book of Mormon that "the face of the whole earth" was changed through terrible earthquakes and other destruction at the time of the Savior's crucifixion. Could it be that today there is no way to reconstruct the geography of pre-crucifixion times?
The answer to that is also in the book. Mormon and Moroni both lived and wrote after the catastrophic changes. They had no trouble identifying locations they personally knew in their lifetimes with places referred to by Alma or Helaman before the catastrophe. Nothing about the precrucifixion geography seems to have puzzled them. The volume itself says that the changes at the Savior's death were mainly to the surface. Bountiful was still in place, its temple still there, when the resurrected Savior appeared (3 Nephi 11:1). Zarahemla was rebuilt on the burned ruin of the former city (4 Nephi 1:8). The narrow pass was still in its key position during the final battles as it had been more than four centuries before. The River Sidon ran the same course, and Ramah/Cumorah, the landmark hill, presided unchanged over the annihilation of its second people. Thus the record itself gives no justification for supposing that the form or nature of the land changed in any essentials, despite the impressive destruction that signaled the Savior's death. Nor is there reliable evidence from the earth sciences to lead us to suppose major changes took place. Nothing we know prevents our placing most of the ancient places on today's map.