Here's a problem to solve: In studying layers of rock sediment, a geologist found an area where older rock was layered on top of younger rock. Which best explains how this occurred?

Among the 4 following options, which is the correct answer?

- A: Earthquake activity folded the rock layers.
 
- B: Volcanic eruptions destroyed a rock layer.
 
- C: Erosion removed several layers of rock.
 
- D: Weathering changed the layering of the rocks.
 