Write in the blank whether the sentence is simple or compound.
1. Earth’s surface seems calm, but its interior seethes with energy.
2. Pressure and heat inside the earth melt rock.
3. Molten rock is lighter than its surroundings; it rises to the surface.
4. Molten rock inside the earth is magma; magma on the earth’s surface is lava.
5. A volcano is formed from magma.
6. Some volcanoes erupt with great power; others are less violent.
7. Thick magma is forced from inside the earth by great pressure.
8. Thin magma flows more easily; moreover, it contains less
explosion-causing gas.
9. Kilauea on Hawaii is an example of a peaceful volcano.
10. Scientists from all over the world observe its eruptions.
11. Mount Saint Helens is another story; the mountain in the state
of Washington literally blew its top in 1980.
12. A chain of volcanic mountains lies across the Pacific Northwest.
13. It is called the Cascade Range, and it includes Mount Saint Helens.
14. Earth is not the only planet with volcanoes.
15. Photographs reveal active volcanoes on the moons of Jupiter
and Neptune and extinct volcanoes on Venus and Mars.