| A | B |
|---|
| mineral | a naturally occurring, inorganic solid that forms on or beneath Earth's surface. |
| crystal | a solid made up of particles that line up in a pattern that repeats over and over again. |
| rock cycle | a series of processes on and beneath Earth's surface that slowly changes rocks from one kind to another. |
| igneous rock | a type of rock formed when molten rock (magma or lava) cools and hardens at or beneath the Earth's surface. |
| sedimentary rock | a type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together. |
| metamorphic rock | a type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions. |
| nonrenewable resource | a natural resource that is not replaced in a useful time frame. |
| ore | rock that contains a metal or other economically useful mineral. |
| smelting | the process by which ore is melted to separate the useful metal from other elements. |
| weathering | the chemical and physical processes that break down rock at Earth's surface. |
| erosion | the process by which water, wind, or ice moves particles of rock or soil. |
| mechanical weathering | the type of weathering in which rock is physically broken into smaller pieces. |
| abrasion | the grinding away of rock by other rock particles carried in water, ice, or wind. |
| ice wedging | process that splits rock when water seeps into cracks, then freezes and expands. |
| chemical weathering | the process that breaks down rock through chemical changes. |
| oxidation | a chemical change in which a substance combines with oxygen, as when iron oxidizes, forming rust. |
| permeable | characteristic of a material that is full of tiny, connected air spaces that water can seep through. |
| soil | the loose, weathered material on Earth's surface in which plants can grow. |
| bedrock | the solid layer of rock beneath the soil. |
| humus | dark-colored organic material in soil. |
| fertility | a measure of how well soil supports plant growth. |
| loam | rich, fertile soil that is made up of about equal parts of clay, sand, and silt. |
| soil horizon | the layer of soil that differs in color and texture from the layers above or below it. |
| topsoil | mixture of humus, clay, and other minerals that forms the crumbly, topmost layer of soil. |
| subsoil | the layer of soil beneath the topsoil that contains mostly clay and other minerals. |
| acidic | describes a substance that reacts strongly with metals and changes blue litmus paper red. |
| basic | a word used to describe a substance that feels slippery and changes red litmus paper blue. |
| litter | the loose layer of dead plant leaves and stems on the surface of the soil. |
| decomposers | an organism that breaks down wastes and dead organisms. |
