Bedrock Base Map Location 2
The rocks seen here, known as the Six Mile Lake Amphibolite, were originally formed from massive lava flows which eventually cooled and hardened into basaltic rocks. Later these rocks were subjected to high temperature and pressure, transforming the lava flows into the metamorphic rock amphibolite. This process caused recrystallisation and the formation of easily visible crystals of hornblende and plagioclase feldspar which are noticeably oriented in a singular direction.
Bedrock exposures south of Groveland Mine, western Upper Peninsula, Michigan | Paleoproterozoic | 1.8 to 2.1 billion years old