“a great way off, at Adam.” Adam is about 25 miles (40 km) north of the Dead Sea. The Israelites would not have needed such a long stretch of dry ground to cross over, so perhaps God did that for such a long way so many Canaanites could see for themselves the power of God.
“the Sea of the Arabah, even the Salt Sea.” This is the Dead Sea.
“Then the people crossed over opposite Jericho.” The Israelites must have crossed over Jordan close to where the modern Allenby Bridge is, which leads into Jericho today. “Crossed over” is a major theme in Joshua because the man Joshua is a type of Christ and the book of Joshua typologically portrays people crossing over from this mortal life into the “Promised Land” of everlasting life (see commentary on Josh. 1:11).