Cross Mountain is the highest peak in the Bear Pond Mountains, a sub range of the Appalachian Mountains. This grouping of mountains straddle the Maryland and Pennsylvania border. Cross Mountain and Hearthstone Mountain 2,021 feet (616 m) which is on the Maryland side, form a unique geologic formation known as the "Punchbowl". This feature was created by the weathered shales of the Ordovician age in the center of a south-plunging anticline, having been eroded to expose a large amphitheater like feature (punchbowl). Cross and Hearthstone Mountain are made of hard resistant quartzite of the Tuscarora Formation of the Silurian age.