Middle Sister also known as "Hope," is a stratovolcano consisting primarily of basalt but also has erupted andesite, dacite and rhyodacite. Last erupting approximately 50,000 years ago, it is considered extinct. The mountain's form is that of a cone which has lost its east side to glaciation. The Hayden and Diller glaciers continue to cut into the east face while the Renfrew Glacier is located on the northwestern slope. The large but retreating Collier Glacier descends along the north side of Middle Sister and cuts into North Sister's west side.
Middle Sister is the smallest and most poorly studied. It is also the middle in age, but only somewhat older than South Sister, with the most recent flows dated to 14,000 years ago.
Read more about this topic: Three Sisters (Oregon)
Famous quotes containing the words middle and/or sister:
“In the middle of the night, as indeed each time that we lay on the shore of a lake, we heard the voice of the loon, loud and distinct, from far over the lake. It is a very wild sound, quite in keeping with the place and the circumstances of the traveler, and very unlike the voice of a bird. I could lie awake for hours listening to it, it is so thrilling.”
—Henry David Thoreau (1817–1862)
“For she has made me the laily worm
That lies at the fit o’ the tree,
An’ my sister Masery she’s made
The machrel of the sea.”
—Unknown. The Laily Worm and the Machrel of the Sea (l. 5–8)