Final answer:
The Black Hills are a geologic structure known as a domed uplift, formed by molten rock pushing the crust into a dome shape.
Step-by-step explanation:
The Black Hills of South Dakota are an example of a geologic structure known as a domed uplift. Dome mountains are formed when molten rock (magma) pushes its way up under the earth's crust without erupting onto the surface. This pressure causes the overlaying crust to bulge upwards into a rounded shape, creating a dome-like feature. Over time, erosion can strip away the upper layers of the dome, revealing the core of igneous and metamorphic rocks.