1. Tuesday, January 17
If we haven't dug a hole to the center of the earth, how do we know it has layers?

4. Sorting by Particle Size and Density
in Lakes, Rivers, and Beaches

5. Big Stuff Falls First
When a mudslide dumps stuff into a lake or the ocean, things settle to the bottom according to particle size and density. The biggest rocks drop to the bottom first.

6. This is a good explanation of what happens… You can also link directly to YouTube by clicking here:

7. If two rocks are the same size, the one that is the densest will end up on the bottom layer.