The Grayling Platform, which was built in 1967, is owned and operated by UNOCAL as a development platform of the Alaska's Cook Inlet McArthur River field. The platform was built in response to the extensive oil and gas discoveries in the Cook Inlet by Standard Oil, Pan American, and Ohio Oil Companies in 1960's. Following the discovery, further field development led to over 35 exploration wells being drilled in the Cook Inlet by various operators on other platforms. Behind the Grayling Platform is Mount Redoubt, also known as Redoubt Volcano. An active volcano located on the west bank of the Cook Inlet, and part of the Chigmit Mountains of the Aleutian Range in the state of Alaska, Mount Redoubt is located approximately 180 km southwest of Anchorage and is the third highest mountain within the range, standing at 2750 m. Mount Redoubt is known to have been active for almost 1000 years and has recorded eruptions in 1902, 1922, 1966, 1989, and 2009. The mountain is made up of pyroclastic flows, which produce large deposits of andesite, basalt, and dacite. The foundation rocks that the volcano sits atop are granites of the Mesozoic Era, derived from the Alaska-Aleutian Range batholith. (Photograph taken on 15 November 2010 by Zachary Mester, Department of Geosciences, Florida Atlantic University, Boca Raton, Florida, USA).