The Hills of Home

Jutting curiously out of the level floor of the Tanana Valley, near Fairbanks, are several small hills. Four of these, including Lakloey, Brown's, Sage and Birch Hills consist partly of basaltic rocks. These rocks were erupted through volcanic vents which cut through older rocks (Birch Creek schist) over 90 million years ago. Some of the basalt contains football-like structures called "pillows" which tell us that these lavas were erupted on the floors of prehistoric lakes or seas. These isolated hills are remnants left from erosion that has carried away surrounding rocks over the years.

Most of the hills composing the uplands between the Chatanika, Chena and Salcha Rivers are composed of Birch Creek schist and younger granitic rocks (60-120 million years old). Clear Creek Butte, Blair Lake Buttes, Moose Creek Bluff and Birch Hill are mainly composed of Birch Creek schist. Rocks composing the Birch Creek schist formation are chiefly recrystallized sedimentary rocks which were first deposited as long ago as Precambrian time (greater than 570 million years).

The Wood River Buttes, which emerge from the Tanana Valley flood plain, are composed of iron-magnesium rich (ultramafic) rocks. These rocks are of igneous parentage, as they have crystallized from a parent melt. Being fairly resistant to weathering, they too have better withstood the ravages of time and now stand as low sentinels on the broad valley floor.