* Boulder: A boulder is a large rock, generally considered to be larger than a hand-sized rock. There's no official size definition, but it's typically anything that requires more than one person to move.
* Pebble: A pebble is a small, smooth rock, typically smaller than a fist. They are often found on beaches or riverbeds.
Here's a table summarizing the key differences:
| Feature | Boulder | Pebble |
|---|---|---|
| Size | Larger than a hand-sized rock | Smaller than a fist |
| Movement | Requires multiple people to move | Can be easily picked up |
| Location | Often found in mountainous regions, riverbeds, and glaciers | Found in beaches, riverbeds, and other areas where rocks are eroded |
It's worth noting that there is some overlap between these terms, and there isn't a strict scientific definition for either. "Cobble" is another term used for rocks larger than pebbles but smaller than boulders.
