What types of volcanoes were erupting 3.8 billion years ago?

Today, we meet a new type of rock and a new type of volcano, far more powerful and dangerous than those we've met so far. The old volcano is long dead, but the scars it left behind can still be seen across the Greenland landscape. Along the way, we'll learn how different types of lavas are made, why a few rocks can float in water, and learn about a field trip Dylan took to Iceland in 2010.

Extra Credit: Eat a grilled cheese sandwich, blow a bubble in gum, or make campfire.