South Sister, also known as "Charity", is the tallest volcano of the trio, standing at 10,363 feet.Its modern structure is no more than 50,000 years old, and it last erupted about 2,000 years ago.
Unlike its sister peaks, South Sister has an un-eroded summit crater about 0.25 miles in diameter that holds a small crater lake known as Teardrop Pool, the highest lake in Oregon.
