Okay kiddo, so do you know what sand is? It's like tiny bits of rock that gets carried around by the wind or water. And sometimes, when layers of these sands pile up over millions of years, it turns into something called a rock formation.
The Upper Greensand Formation is one of these rock formations that was formed in England a really, really long time ago. It's made up of a type of sandstone that was created by a combination of sand, shells, and a type of green clay.
Now, when this Upper Greensand Formation was formed, it was actually under the ocean! And over time, the sandy layers that make up the formation got compacted under the weight of all the water above it. And as the ocean slowly receded, it left behind this rocky layer.
So now, when people study the Upper Greensand Formation, they can tell a lot about what the environment was like millions of years ago. They can see what types of creatures lived in the ocean, what kind of plants were growing on land, and even what the climate was like at the time. Pretty cool, huh?