| A | B |
|---|
| volcano | weak spot in the crust where molten material, or magma, comes to the surface |
| magma | molten mixture of rock-forming substances, gases, and water from the mantle |
| lava | magma that has reached the surface |
| Ring of Fire | a major belt of volcanoes that rims the Pacific Ocean |
| island arc | a string of islands formed by the volcanoes along a deep-ocean trench |
| hot spot | an area where magma from deep within the mantle melts through the crust above it |
| physical property | any characteristic of a substance that can be observed or measured without changing the composition of the substance |
| chemical property | any property that produces a change in the composition of matter |
| viscosity | the resistance of a liquid to flowing |
| silica | a compound made up of particles of the elements oxygen and silicon; one of the most abundant materials in Earth's crust |
| pahoehoe | fast-moving, hot lava that has low viscosity; surface looks like a solid mass of wrinklges, billows, and ropelike coils |
| aa | slow-moving, cooler lava that has a higher viscosity; forms a rough surface of jagged lava chunks |
