What is the oldest major slice of rock, one that's relatively well-preserved, one that's fueled a half-century of research?

The episode's name kinda gives it away, but stay tuned as we meet the last location of Season 2: a series of rocks near Greenland's capital. Along the way, we'll meet the different groups of people who have settled on this remote island, and a geologist from the other side of the world. I'll also take a brief detour into why I unfortunately can't talk about every single ancient rock out there.

Extra Credit: Find a choir to sing in, or play some ping-pong.

Why are some ancient rocks well-preserved, while others are extremely messed up?

Today, we'll take a side quest from our Greenland arc to learn more about metamorphosis, which changes rocks beneath our feet. On the way, we'll transform toast into cookies, take an elevator ride deep into the crust, and meet an ancient rock with a babyface.

Extra credit: make some toast, or go looking for butterflies.