What are the plutonic features called that form when magma cools?

Plutonic features are formed from magma that cools and solidifies beneath the Earth's surface. The correct answer, which includes sills and dykes, refers specifically to two types of intrusive igneous formations.

Sills are horizontal sheets of igneous rock that form when magma intrudes between existing rock layers. This process occurs at depths below the surface, allowing the magma to cool slowly and crystallize into solid rock. Dykes, on the other hand, are vertical or steeply inclined intrusions that cut across existing strata, also formed through the cooling of magma.

Both sills and dykes are significant in their geological context as they help to illustrate the processes of magma movement and solidification below the Earth’s surface. Such features can influence the geological landscape and provide evidence of historical volcanic activity.

The other options do not focus specifically on these subterranean formations. Volcanoes and craters are related to surface eruptions, batholiths and laccoliths also pertain to large intrusive formations but are broader categories that do not directly address the specified features. Fissures and faults refer to fractures in the Earth's crust and are associated with tectonic activity rather than the cooling of magma.