vocabulary 15

Rock: a natully formed solid in the crust,made up of ome or mlre minerals.

igneous rock: a rock formed when melted rock material cools and hardens.

sedimentary rock: a rock made of bits ofmatter joined together.

fossil: any remains or imprint of living things of the past.

metamorphic rock: a rock formed under heat and pressure from another kind of rock.

humus: decayed plant or animal material in soil.

pollution: adding any harmful subtances to Earth´s land,water,or air.

rock cycle: rocks changing from one form  into another in  a never-ending series of process.