Here's why:

* Ductile deformation occurs when rocks are subjected to stress over a long period of time and at relatively high temperatures. This allows the rock to bend, fold, and flow without breaking. Think of how you can mold clay – it changes shape without shattering.

* Brittle deformation, on the other hand, occurs when rocks break or fracture due to sudden stress. This is what causes earthquakes.

Key characteristics of ductile deformation:

* Folding: Rocks bend and curve into folds, like a series of waves.

* Flowing: Rocks can even flow like a very viscous liquid over long timescales.

* No sudden releases of energy: Because the deformation is gradual, it doesn't produce seismic waves or earthquakes.

Examples of ductile deformation:

* Mountain ranges: The folds in mountains are often the result of ductile deformation.

* Metamorphic rocks: The intense heat and pressure involved in metamorphism can lead to ductile deformation.

* Deep within the Earth's mantle: The rocks in the mantle are under enormous pressure and are hot enough to flow slowly over time.

Let me know if you have any other questions!