We were talking about asteroids and how they crash into planets leaving craters.
We saw how different sized asteroids can make different sized craters (we measured the size of the craters in relation to the size of the craters....and plotted these on a graph!)
We then talked about how an asteroid crashing to earth could have killed off some of the dinosaurs. Then some dinosaurs must have been killed by the dust or shock waves from the impact, and finally many many more dinosaurs must have been killed off when the dust and debris from the impact would have blocked the sun's light and heat causing a huge ice age. This ice age would have meant that some dinosaurs might have died of the cold while others must have starved to death when plants couldn't grow in the cold.