Which is kind of amazing. The magnetic field is produced by some remarkable result of the convection of molten hot iron alloys in the core of the Earth. Kind of hard to really get your head round if you’re sitting calmly at your desk or walking on a nice stable surface. Periodically, the poles switch round it seems but at the moment the magnetic South pole is actually near the point we’d normally call the geographical North pole. They’re pretty close, but the geographic axis doesn’t exactly coincide along the geographic axis of rotation of Earth. And the lines of force go from magnetic North to magnetic South so your compass needle is actually pointing towards magnetic South. Remember iron filings and bar magnets from physics class?

Earth is a big magnet.

The key to getting the whole thing the right way round in my mind is to remember that you need to cling tight (tite) to the ceiling. Once that’s established, you have a letter C in stactite that fits cling and ceiling. And stalagmites, with its cheeky G, naturally then is the other one which would grow on the ground. Sorted?

Stalactites, Stalagmites

Meteor: A rock burning up as it enters the atmosphere. Also known as a shooting star.

Meteorite: Parts of a meteor that made it all the way to the ground. Look out!

It was a long time before I really knew the difference between these things.

Asteroids, meteors and meteorites

Divergent (Mid-Atlantic ridge, The Rift Valley), Convergent (The Andes, The Himalayas) and Transform (San Andreas fault, Dead Sea Transform). There are some sub-varieties but these are the main ones. Which makes natural sense, so there’s no remembering to do, when you have two contacting plates - they can either be pushing together, pulling apart or rubbing past each other.

Incidentally, the idea that the giant continents move around all the time, enough to pull apart South America and Africa, and thrust up the Himalayas, obvious as it may seem now, was once not at all obvious. And if you stand on the ground in a big landscape, it’s kind of amazing to think of just what an amazing notion it was to propose. I read about it in Bill Bryson’s, A Short History of Nearly Everything for which I found a relevant excerpt online - The Earth Moves (pdf) - should you be interested in the characters that had the courage to seriously propose it.

Tectonic plate interaction boundaries

A large boulder, transported and deposited by a glacier. This is my favourite location for glacial erratics. Bonus points if you can tell where it is.

Sketchplanations tagged with geology