Map of the Dalmasca Westersand
Click on the map below to see the enlarged version.
The team will arrive at the Western Divide after the sequence aboard the Dreadnought Leviathan. The easiest way to reach the Zertinan Caverns is through the Dalmasca Westersand and the Earth Tyrant side quest takes place in the Wyrm's Nest area in the north.
There is a treasure chest in the south-east section of the Windtrace Dunes; specifically, the area that you can only reach by entering through the Shimmering Horizon. The treasure chest contains a Diamond Armlet.