Crater Lake, in Oregon, was formed around 7,000 years ago after the eruption of Mount Mazama. There are no rivers flowing into or out of the lake but the amount of rain and snowfall ensures that every 250 years the total amount of water is replaced. For this reason, Crater Lake has some of the world's purest water. It is famous for its clear, deep blue colour - which is represented in this stamp. This is one of a set of 10 stamps issued from July - September, 1934 to commemorate National Parks Year.
for lakes and/or rivers