3 Nephi 8:19, 23. Darkness for 3 Days?
The darkness in Judea, where Christ was crucified, lasted three hours. In the New World (“this land,” Helaman 14:20), it lasted for three days and may have had a different cause, in this case volcanic. Three days of darkness have been reported for other volcanic eruptions that filled the air with ash. We do not know what caused the darkness in faraway Judea.
The thick darkness and other cataclysmic phenomena recorded in 3 Nephi 8 are typical of volcanic eruptions. See the discussion in John A. Tvedtnes, “Historical Parallels to the Destruction at the Time of the Crucifixion,” in Journal of Book of Mormon Studies 3/1 (Spring 1994) and Bart J. Kowallis, “In the Thirty and Fourth Year: A Geologist’s View of the Great Destruction in 3 Nephi,” BYU Studies 37/3 (1997-98).