What you will learn in Plate Tectonics

1. 1. The fit, and why it was not enough

   South America fits into Africa, and everybody could see it. Wegener assembled four more lines of evidence and was rejected anyway, for a reason that was correct.

2. 2. The plates

   A plate is not a continent. The largest plate on Earth contains no continent at all, and most plate boundaries run nowhere near a coastline.

3. 3. Three ways to meet

   Two plates can move apart, together, or past each other. What that produces depends on what the plates are made of — and convergence does not always make volcanoes.

4. 4. The barcode

   The module's centre. Predict what a magnetometer towed across a mid-ocean ridge will record, then look — and the answer shows the seafloor is the part that moves.

5. 5. Why plates move

   Three forces are candidates. One of them dominates, and the way to find out which is to sort a table — including by a column that does not work.

6. 6. Measuring the present

   Plate velocities are measured to better than a millimetre a year. Every one of them is meaningless until you say what it is measured against.

7. 7. Running it backwards

   Two hundred and fifty million years in twenty seconds — and the part of the animation that is evidence, against the part that is a convention.