He said the Cambrian disaster had shocked other miners, partly because it was considered to be a modern coalmine.

BBC: NEWS | UK | Wales | South East Wales | Fatal mine explosion remembered

Serving as a psychological canary in the coalmine of your life, warning you to re-evaluate the wisdom inherent in following one particular path relative to alternative ones.

FORBES: Worried About Anxiety? Don't Be; It's Often Good For You.

After the war, the communists decided to exploit a huge coalmine underneath it, swelling the population to 70, 000 housed in block after block of hideous high-rise concrete hulks, utterly devoid of a sense of community.

ECONOMIST: Saxon snapshots

Since the Arctic as a whole is responding to climate change earlier and more acutely than the rest of the planet, we should think of it as an early warning system -- a proverbial canary in a coalmine.

CNN: Next global warming worry: Thawing tundra