Bill Nye the Science Guy (1993) : 5x10

What do you get when you have a big hole in the ground and some water? Lakes and ponds. All lakes and ponds have one thing in common – they happen when a basin, or hole, forms, and then fills with water. A glacier may grind a long gulch, volcanoes and earthquakes may make a sinkhole, or engineers may build a dam – they can be human or beaver.