Volcanoes

2. spot a small volcanic regions a few hundred kilometers across
3. particles that range in size from small beads to walnuts
4. particles larger than 64 millimeters in diameter
5. volcanic activity that occurs within a plate
8. type of boundary where plates go in different directions and form volcanoes
10. when pressure drops enough
12. a landform made of magma that hardened in the volcano's pipe and later was exposed by erosion
15. affect characteristics of lava flow
18. repeated eruptions of lava or pyroclastic material eventually build a mountain
19. a steep-walled depression at the summit of volcanoes
20. another name for composite cones
21. when blocks are ejected as glowing lava

1. particles produced in volcanic eruptions
6. molten rock beneath earths surface
7. produced by the accumulation of fluid basaltic lavas
9. a subtance's resistance to flow
11. magma outside of the volcano
13. type of basaltic lava that forms rough, jagged blocks with sharp, spiny projections
14. ejected lava fragments that harden in the air and build this volcano
16. a long belt of volcanoes that circles much of the Pacific Ocean
17. type of basaltic lava that forms relatively smooth skin that wrinkles as lava continues to flow