Toyota Repair: Radiator Problem, radiator fluid, geo prizm

Question
My car has a radiator with a slow leak.  Every 4 or 5 months (maybe longer) it gets low enough that the temperature gauge (and the steam from under the hood) cause me to add radiator fluid.

This time something different happened.  I left the house in the morning.  I came back home in the middle of the day for 30 minutes.  Then I left again.  When I came home in the evening I saw radiator fluid all over the garage floor.  I think this happened during the 30 minutes it sat in the garage in the middle of the day.

What would cause this and what should I do about it?  By the way, I have a 95 Geo Prizm, which of course, is similar to a 95 Carolla.

Answer
Possibly the small leak got bigger and that's why all the coolant is on the floor, did you notice if the engine overheated?
When an engine overheats to a certain degree the high pressure generated in the cooling system will force the radiator cap open and try to put the extra coolant into the overflow bottle, once the bottle is full the coolant exits through the vent hose, put some water into the radiator when the engine is cool and see where the leak is coming from without starting the engine, a large leak will show immediately, you may have to have the system pressure checked to find a leak, if there is no external leak the engine could be overheating, some of the most common causes is the thermostat stuck closed or possibly a clogged radiator.