Rilles on the Moon appear to be collapsed tunnels. Planetary scientists believe these tunnels were originally filled with
A) liquid water.
B) molten rock.
C) steam.
D) carbon dioxide.

Question

Quizplus · Accepted Answer

Rilles on the Moon are believed to be the result of volcanic activity, where molten rock (lava) once flowed beneath the surface, creating tunnels. When the lava drained away, these tunnels collapsed, forming the rilles observed today.

Rilles on the Moon Appear to Be Collapsed Tunnels