Geologists get excited by old rocks because the Earth is ~4.5 billion years old, but early rocks have been destroyed by bombardment or the tectonic rock cycle. Old rocks (>3.5 billion years) in outcrop are very rare and exciting to find - they tell us about how the early Earth worked. 4/6

The irony of geology in the tundra is the rocks have been conveniently exposed by a continental-scale glaciation, but close up they are covered in lichen. So a pressure washer was brought in to clean up one outcrop to get a better look at the gneiss (remember this is a *long* way to the store). 5/6