Re: What are good ways to explain 'geologic time' to a class of 6th graders?

The most effective way is to show them something really big, and then
show them the fraction that corresponds to the amount of time we've
been around.

Take them to New York City, show them the World Trade Center, and mention
that if this is the age of the Earth, man's time on the planet is the top
however-many inches of the building.

Take them out on the school's track and make them walk around it a few
times until they're all exhausted, then point out the few inches or so
that correspond to "modern times".

You can also use this to demonstrate how much money Michael Jordan makes
in a year compared to what they will make in their combined lifetimes.