Volcano

Amy: Sometimes magma can find one of those fissures and rise up through it.

Roark: What's magma?

Rachel: Lava.

Roark: Lava? Right here in L.A?

Amy: It is one of the possibilities.

Roark: We have a history of that here in the downtown area?

Rachel: Paricutin... 1943, a Mexican farmer sees smoke coming out of the middle of his cornfield. A week later there's a volcano a thousand feet high. There's no history of anything until it happens. Then there is.