Here's why:
* Ductile strain occurs when rocks deform under high pressure and temperature. The rock behaves like a plastic, flowing and changing shape without breaking. This results in permanent changes to the rock's structure and often creates folds.
* Brittle strain occurs when rocks break under stress. This results in fractures and faults, which are permanent changes, but the rock itself isn't fundamentally altered in the same way as with ductile strain.
Here's an analogy:
* Imagine a piece of clay. If you press on it gently, it will deform and retain the new shape (ductile).
* If you hit the clay with a hammer, it will shatter (brittle).
So, while both ductile and brittle strain cause permanent changes in rocks, ductile strain involves a more fundamental and pervasive change in the rock's structure.
