Where it all began/geological history
The bedrock of Glacier Bay is not well documented because the widespread folding of the layers of rock, metamorphism (the change in sedimentary and igneous rocks that results in metamorphic rocks), and intrusive rocks (formed deep inside the earth as opposed to outside it) interfere with the stratigraphic record. The stratigraphic record is the way that different types of rock have layered themselves in an area's bedrock. The rock under Glacier Bay is mostly made up of Schist, Horn-Blende Schist, Biotite, and Gneiss.
- Schist - A metamorphic rock which contains particles of mica, direct pressure is involved in it's formation.
- Horn-Blende Schist - A variety of schist which contains needles of hornblende
- Biotite - A common mineral in the Mica family.
- Gneiss - A metamorphic coarse-grained rock with elongated mineral grains due to pressure.
The main reason that the park has such an an altered stratigraphic record and a large quantity of intrusive rocks is because two major fault lines where the Pacific Plate and Continental Plate meet lie directly on the outer coast of the park. The movement of these plates and other factors contribute to the folding, metamorphism, and intrusive rocks.