The colored minerals of the Keweenaw are found in veins and in the tops of lava flows, where they fill holes left by bubbles when the lava flow was degassing and cooling after being extruded. The colored minerals change the tone of the rock, in this case from black to green, reflecting the color of the amygdaloidal minerals. At this place along the road (watch out for speeding vehicles!) you can see where the greenish flow top crosses the road.  Realize that these lavas were flat-lying when they cooled and have since been tilted westward to about 55 degrees. Look on the other side of the road where the same greenish rocks occur, and then reconstruct the old flow surface and its 55 degree dip to the west.





Why are the amygdules elongated? How can we use this to our advantage?

Did the amygdules fill after the lava flow cooled? When did the flow top turn green?