North and South Twin Lakes are two nearly identical natural lakes in Deschutes County, Oregon. Both were formed around 20,000 years ago when a rising magma reservoir reached groundwater, creating violent steam explosions. Two craters were formed, later filling with water. North Twin Lake has an elevation of 4340 ft, while South Twin Lake is 6 ft lower, at 4334 ft. North is larger, having a surface area of 112 acre, compared to South's 99 acre. North is also deeper, with an average depth of 40 ft and a maximum depth of 60 ft. South is shallower, with an average depth of 33 ft and a maximum depth of 58 ft. In 1987, the Oregon Department of Fish and Wildlife poisoned South Twin Lake to remove rough fish. The lake is stocked with fingerlings and rainbow trout. North Twin Lake was illegally stocked with catfish some time before 2008. The largest recorded rainbow trout caught from South Twin Lake weighed over 13.5 lbs. The trout average 10 to 14 in long, with 18 in fish common. The Twin Lakes have surprisingly calm winds compared to other Cascade Lakes. South Twin Lake is completely tree-lined except for the beach day-use area. Water levels vary little over the season. The lake is rich with weedbeds.