Behold, I am Amaleki, the son of Abinadom. Behold, I will speak unto you somewhat concerning Mosiah, who was made king over the land of Zarahemla; for behold, he being warned of the Lord that he should flee out of the land of Nephi, and as many as would hearken unto the voice of the Lord should also depart out of the land with him, into the wilderness.
Sorenson and Gardner locate the land of Nephi in or around the vicinity of Kaminaljuyu. If they are right, then Mosiah I's exodus was actually part of a bigger movement of people from that area.
"Archaeologist Marion Hatch and her Guatemalan colleagues have encountered evidence for the existence of a now-extinct lake around which the earthen platforms of Kaminaljuyu were arranged, as well as a sophisticated system of intensive agriculture. Connected with the lake were various irrigation canals, one of which carried water to an artificial storage basin 52.5ft(16m)wide and 36ft(11m) deep; leading from the latter were small tributary channels which brought water to the fields, some of which were agricultural terraces on the sides of the ravines. As the lake dried up about 200BC, perhaps due to over-exploitation of the land, or even to tectonic movements(the region is highly earthquake-prone), the city dwindled until its revival during the Early Classic period"(The Maya 7th Edition, pg 72),emphasis added.