Another theory is that warfare in Alaska or a desire to seek out new resources of iron for making tools such as knives may have encouraged people to move eastward. Archaeologists have used the distribution of early Alaskan-style harpoon heads to track the routes taken by Thule people. One route follows the Beaufort Sea coast and Amundsen Gulf, entering the High Arctic via Parry Channel and Smith Sound. A second route led the Thule south, along the western coast of Hudson Bay.