It's important to understand that while we think of rock as rigid and solid, under extreme pressure and over very long periods, rock can behave like a very viscous fluid. This is due to:

* High pressure: Deep within the Earth, the immense weight of the overlying rock creates enormous pressure.

* High temperatures: The Earth's interior is incredibly hot.

* Time: Geologic processes happen over millions or even billions of years.

Examples of Rock Flowing:

* Mountain formation: The movement of tectonic plates causes rock to buckle and fold, creating mountains. The rock doesn't just break; it deforms and flows under extreme pressure.

* Continental drift: The Earth's continents are constantly moving due to the movement of tectonic plates. This movement is possible because the rock deep within the Earth behaves like a very viscous fluid over extremely long timescales.

* Lava flows: While lava is molten rock, the way it flows and spreads across the Earth's surface is a good analogy for how solid rock can behave under pressure.

Note: Rock can also be brittle and break instead of flow. This is more likely to occur at shallower depths where the pressure is lower.