Right click on your map to add a "specific point" on it.
Latest version of the Map by Ecarlberg with volcano Island http://steamcommunity.com/sharedfiles/filedetails/?id=867211046
On the following maps, Volcanic Island not included. The images below are the map from Out of Reach. Click on them to view a full size image.
Map with Caves and Treasure Chests Marked
Spoiler Alert: The caves and spawning location of the treasure chests are marked on the following maps.