See this a post referring to Richard Hess' article in the Zondervan Illustrated Bible Backgrounds Commentary.
Adam Zertal has suggested that an early Iron Age installation located on Mount Ebal is actually an altar. The main structure is approximately nine by seven meters and preserved to a height of 3.27 meters. The structure was filled with a stratum of fieldstones, earth, ashes, pottery, and animal bones. Zertal finds support for his identification in the Mishnah’s description of the second temple altar. Furthermore, Zertal suggests that this installation is the altar described in Joshua 8:30-35. But some have not been persuaded by Zertal’s identification and suggest that the structure is not an altar but a watchtower.
 Adam Zertal, “Has Joshua's Altar Been Found on Mt. Ebal?,” Biblical Archaeology Review 11, no. 1 (1985): 26–43.
 Aharon Kempinski, “Joshua’s Altar-An Iron Age I Watchtower,” Biblical Archaeology Review 12, no. 1 (1986): 42, 44–49. For Zertal’s response see Adam Zertal, “How Can Kempinski Be So Wrong,” Biblical Archaeology Review 12, no. 1 (1986): 43–53.