The geologic history of the west coast is a long and tumultuous one. 1.5 to 2 billion years ago, the ancient supercontinent of Pangea drifted to the west and bumped in the smaller subcontinents of Columbia and Rodinia. The collision caused tectonic plates to smash the ocean floor, suppress the layers of sand and marine sediment and ocean plates overrode each other and volcanic cracks opened up in the earths crust and basalt begin to flow out in successive layers of basalt that covered all. Over the next 2 billion years , or so many plates and continuous basalt emmissions collided one over another, vulcanism occurred all along the area, more sediment was deposited from the rising landmass, and the west coast of the North American continent rose and fell continuously.
About 150-120 millions years ago, a major plate movement and release of massive volcanic activity throughout the whole of the western U.S, pushed up and formed what is now the Cascade mountain range, which transects WA, OR, and Ca on a north to south axis. Many of the volcanic mountains we now see and enjoy began to form and rise during this area. Mt Baker, Mt. Rainier, Mt St. Hellens in Washington,Mt. Hood in Oregon and Mt. Shasta and Mt. Lassen in California are prime examples. At the same time many layers of the surrounding sedimentary layers, some from the ancient Pangeal Sea deposits were folded, compressed, and metamorphosed due to heat and pressure, from layers of basalt being deposited from the magma being released from the earths ever cracking crust.
One such formation, composed of sand, sediment, and even fossiled marine organisms from the ancient seabed, was thrust in one solid chunk of rock, older than the formations under it, became the mountain now known as Mt. Shuksan, located 5 miles east of present day Mt. Baker in Whatcom county Washington. This mountain is composed of a semi-solid kind of rock, unique to the country rock around it, known in geologic terms as Shuksan Greenschist. Its' uniqueness is unusual due to the different composition of the rock. It consists of marine sediment, mixed with sedimentary layers, mixed and twisted with igneous intrusions, high silicate content, and due to high pressure, metamorphosed into one solid rock. It is special due to the many amphiboles(smaller pieces trapped inside the main rock) and a high content of lawsonite(metamorphic rock high in the mineral silicon). Silicon is the mineral that forms quartz, the second most common mineral in the earths crust. Quartz deposits are where gold is formed, which makes it very popular by todays standards!
Over the four continental gaciation periods the ice advanced and retreated over the area, making the plateaus of eastern WA and carving out Puget Sound, and the valleys of western WA. Rivers formed in the valleys and western WA is now a string of river valleys running east and west. When the last glacier receded at the end of the Quaternary Period, about 15,000 yrs ago, Mt Shuksan is the mountain we see today. Glaciated, active advancing and retreating glaciers, a summit pyrimid, known as a horn(just like the more well known Matterhorn, in Switzerland), And one of the most photographed mountains in the U.S. today. It is a picture in every travel brochure published for tourists coming to visit the wonderful state I call home.
Here are some pictures of Shuksan and the rocks that make it.Hope you enjoy it, sorry for the long winded thesis, but this is a unusual piece of geology and hope anyone will like the pictures, at least!