|Elevation||1,559 m (5,115 ft)|
|Length||16.6 mi (26.7 km) WNW–ESE|
|Width||3.9 mi (6.3 km)|
|Age of rock||20–25 mya (Late Oligocene to Early Miocene)|
|Type of rock||Volcanic plugs|
The Nine Sisters or the Morros are a chain of twenty-three, although typically only nine are included, volcanic mountains and hills in western San Luis Obispo County, Southern California. They run between Morro Bay and San Luis Obispo.
The peaks were created more than 20 million years ago during the Miocene Epoch of the Neogene Period, as volcanic plugs of magma which welled up and solidified inside softer rock which has since eroded away. Every plug, with the exception of just two, formed in a nearly straight line.
The peaks in order from Morro Bay to San Luis Obispo, including their height, a sortable table.
|Morro Rock||576 (176)|
|Black Hill||665 (203)|
|Cerro Cabrillo||911 (278)|
|Hollister Peak||1,404 (428)|
|Cerro Romauldo||1,306 (398)|
|Chumash Peak||1,257 (383)|
|Bishop Peak||1,559 (475)|
|Cerro San Luis Obispo||1,292 (394)|
|Islay Hill||775 (236)|
The Nine Sisters are a chain of volcanic plugs composed predominantly of dacite. About 20 to 25 million years ago, magma welled up underneath a layer of softer rock and solidified. The softer overlying rock has since eroded away, leaving a distinct rugged shape.
- "The Nine Sisters of San Luis Obispo County". Sierra Club San Luis Obispo. Archived from the original on 2017-02-14. Retrieved 2009-06-25.