Final answer:
Folds are geological features that indicate deformation in the Earth's crust due to compressional stress. They are evidence of tectonic forces shaping the Earth over long periods of time.
Step-by-step explanation:
Folds are a common geological feature that indicate deformation has occurred in the Earth's crust. Deformation refers to the changing of the shape or structure of rocks due to tectonic forces. Folds are a result of compressional stress, usually associated with plate tectonics.
When rocks are subjected to intense pressure from converging tectonic plates, they can bend and fold instead of breaking. This process occurs over millions of years. Folds can form in various shapes, such as anticlines and synclines.
Imagine you have a piece of paper and you push it together from both ends. The paper will fold, creating curves. This is similar to what happens to layers of rock during tectonic activity. In summary, folds indicate that rocks have undergone deformation due to compressional stress from tectonic forces. They are evidence of the immense pressures and forces that shape the Earth's crust over long periods of time.