The large cracks in the crust that allow lava to ooze out and form extrusive igneous rocks are called fissures.

Here's a breakdown:

* Fissures: These are long, narrow cracks in the Earth's crust. They can be anywhere from a few feet to several miles long.

* Lava: Molten rock that erupts from a volcano or fissure.

* Extrusive Igneous Rocks: Rocks formed when lava cools and solidifies on the Earth's surface.

Examples of how fissures form extrusive igneous rocks:

* Flood Basalts: Vast plains of basalt rock formed by massive outpourings of lava from fissures.

* Mid-Ocean Ridges: Underwater mountain ranges where new oceanic crust is formed by eruptions along fissures.

* Continental Rifts: Areas where the Earth's crust is being pulled apart, resulting in fissures and volcanic activity.

Let me know if you want to learn more about specific types of fissures or extrusive igneous rocks!