The Geological Puzzle of Southeast Alaska

Sawyer Glacier in the Tracy Arm/Ford’s Terror Wilderness Area, southeast Alaska

The geology of southeast Alaska is a complex puzzle that sets the background for everything we see and do in southeast Alaska aboard the Ursa Major.  From the Waterfall Coast of eastern Baranof Island, to the glacially carved mainland fjords of the Tracy Arm/Ford’s Terror Wilderness Area, our trips are framed by the interaction of land and sea.

The Mainland Coast Mountains of Southeast Alaska

Geologists are still pondering why southeast Alaska is shaped the way it is today.  The variety of rock found here is somewhat of a mystery, ranging from igneous (Mount Edgecombe near Sitka), to metamorphic (the mainland Coast Mountains of southeast Alaska), and to sedimentary (the limestone bluffs of Kuiu Island and Prince of Whales Island).

The Unique Ultramafic Igneous Rock of Red Bluff Bay, Baranof Island, southeast Alaska

On Baranof Island, Red Bluff Bay presents an interesting picture.  This type of red rock (ultramafic igneous rock) is found no where else in southeast Alaska, and is quite a site on approach to the bay.  The bright red color of the rock comes from the oxidation of the iron-rich rock surface.  Very little grows on the red rock, as the chemical weathering of the red rock produces poor soil and stunts plant growth.

For an interesting article from the Sitka, Alaska, NPR station regarding the unique geology of southeast Alaska, please click HERE.

A great book for additional information on the geology of Southeast Alaska is: “Geology of Southeast Alaska: Rock and Ice in Motion” by Harold H. Stowell.