Time flies when you live on a seriously unstable planet

Time lies heavy on the hands of telly programmers in the languid holiday month of January. Yawning chasms open in the schedules where housewives, teenage girl detectives, survivors or pop idols used to be.

These voids get filled with re-runs, old movies, obscure sport and perkily composed natural history documentary series. It's the sort of seasonal fare that gives free-to-air purists some idea of what they're missing out on from pay TV.

Tonight's Time Machine (TV One, 7.30pm), for example, is just what you might find on the Discovery Channel (in fact it's a co-production between it and the BBC.) It has the hallmarks of those overexcited offerings: a narration forever building to fever pitch, endlessly repeated CGI sequences promising that we're to be taken on a "wild ride", and a script aimed at the bottom half of the C stream for the feeble-minded.

If we overlook these flaws, however, Time Machine has its fun moments. Only the BBC would transport a soberly dressed Englishman by armchair from the comfort of his lounge back in time to the top of a vast mountain range or far beneath the sea. There was something wonderfully nutty about racing round the Jurassic via La-Z-Boy.

Another commendable feature was that New Zealand, in last's week first of three instalments, played a starring role. Geological instability, after all, is a Kiwi speciality. The Franz Josef Glacier got the CGI whiz treatment in the opening segment about the dramatic effects of ice ages on the planet's landscapes.

And the huge Wellington earthquake of 1855 was another CGI highlight, showing how the land now housing the city's airport and parts of its motorway system just reared up overnight. Those who have suffered the "singularly scary" experience (as a recent commuter so memorably put it) of landing in Wellington in a high wind, might not wish to thank the earth gods for that one.

In other parts of the show we learned that while faith might be able to move mountains a more literal method is to send a big chunk of land like India shoving into a continent. India's pushiness has moved Mt Everest one metre since George Mallory made his first attempt to climb it - perhaps not far enough to lose track of its whereabouts but impressive nonetheless.

Time Machine might be saddled with an unfortunate script but this is counterbalanced by the sheer terror of the message. For example, we learned that Yellowstone National Park in the United States sits atop the world's largest volcano, one which is overdue a mega-eruption by 20,000 years.

Sobering stuff at a time of year when many of us have the leisure to contemplate the nature of our fate. If your troubles are in the little league of, say, that credit card blowout over Christmas, catch this show and give yourself something significant to worry about.

Time and tide might wait for no one but with two episodes to go, it's not too late to catch up on the shaky future of our planet.