The Finny River, rising from the south-east of the lake drains into the southwest part of Lough Mask.

There are several extinct volcanoes in locations like Armagh, Dublin, Offaly, and the Loch na Foeey in Galway.

The area around Loch Na Fooey is known as the site of the ancient "Finny volcano" (490 million years ago).

[3] The volcano's landform is now gone but some of volcanic rocks are preserved in the area, including pillow lavas, and breccia.

[citation needed] The waters hold a range of fish including wild brown trout and pike.