According to science they were first formed when the glaciers slid over the land causing that valleys and mountains that we have today.
Answer:
is an instrument used to measure and quantify the amount of light that emanates from a celestial body.
Not as old as those found in deeper layers
Answer:
All of them having common criteria such as a habitable climatic zone, the proximity of large river basins and geographical isolation from other regions of the world by mountains, deserts or seas
Explanation:
https://www.worldatlas.com/articles/what-is-a-culture-hearth.html