Corrected sentence:
A volcano is a hole in the Earth's crust where hot lava comes out.
Why this is better:
- Only the first word is capitalized: "A volcano..." (writing in ALL CAPS is not needed).
- Adding "the" before "Earth's crust" is correct English: we say "the Earth's crust."
- "Comes out" or "flows out" sounds more natural and simple than "spills out."
Simple explanation for a 6-year-old:
- A volcano is like a mountain with a hole on top.
- Hot, melted rock called lava can come out of that hole.
- When a volcano erupts, lava and ash can flow or shoot out, so people watch from far away to stay safe.
Short alternative sentence: A volcano is a mountain with a hole that lets hot lava come out.