On the Schoodic Peninsula in Maine, diabase dikes intruded an older granite.
Diabase is the equivalent of basalt that solidified underground.
The diabase intruded upward from the mantle into fractures in the overlying granite.
This occurred 195 million years ago and many kilometers underground.
Erosion has now exposed these dikes at the earth’s surface.
They record the early Jurassic rifting of North America from Gondwana and the birth of the Atlantic Ocean.
