Find the line in a cliff where the dinosaurs ended

The cliffs at Zumaia are flysch: layer after layer of rock laid down on the seabed, then tipped on their side like a fallen stack of plates. Read from one end to the other, they hold more than fifteen million years of the Earth's history, and researchers come from all over the world to read them.

The way to see them is from underneath. A small boat leaves the quay in Zumaia and runs along the foot of the cliffs for about three quarters of an hour, close enough to count the stripes. It only goes when the sea allows; on a rough day the boat stays in and the cliffs are seen from the path along the top.

Somewhere in the stack, at a cove called Algorri, is a thin dark line. It was laid down when an asteroid hit the other side of the planet, and below it there are dinosaurs and above it there are not. Further along, geologists have put two golden spikes into the same cliffs to mark where two ages of the Earth begin, which is as close as geology gets to a medal ceremony.