Rock: A solid natural material made of one or more minerals
Igneous rock: Rock formed when melted rock cools and hardens
Sedimentary rock: Rock formed when sediments are pressed and cemented together
Metamorphic rock: Rock changed by heat and pressure
Magma: Melted rock beneath the surface
Lava: Melted rock that has reached the surface
Intrusive igneous rock: Igneous rock that cooled slowly underground, with large crystals
Extrusive igneous rock: Igneous rock that cooled quickly at the surface, with small crystals
Granite: A light-colored intrusive igneous rock with visible crystals
Basalt: A dark, fine-grained extrusive igneous rock
Obsidian: Natural volcanic glass
Pumice: A light igneous rock full of holes that can float
Rhyolite: An extrusive rock with the same makeup as granite
Gabbro: A dark intrusive igneous rock
Sandstone: Sedimentary rock made of cemented sand grains
Limestone: Sedimentary rock made mostly of calcium carbonate
Shale: Sedimentary rock made of compacted clay and mud
Conglomerate: Sedimentary rock with rounded pebbles cemented in it
Breccia: Sedimentary rock with angular fragments cemented together
Coal: A sedimentary rock made from ancient plants
Chalk: A soft, white form of limestone
Marble: Metamorphic rock formed from limestone
Slate: Metamorphic rock formed from shale; splits into flat sheets
Quartzite: Metamorphic rock formed from sandstone
Gneiss: A banded metamorphic rock formed from granite or similar rocks
Schist: Metamorphic rock that shines with mica flakes
Phyllite: Metamorphic rock between slate and schist
Weathering: Breaking down of rock by wind, water, ice or plants
Erosion: Moving of weathered material from one place to another
Deposition: Dropping of sediments in a new place
Sediment: Small pieces of rock, shell or soil moved by water, wind or ice
Compaction: Pressing sediments together under weight
Cementation: Minerals gluing sediments together
Lithification: The process that turns sediment into rock
Rock cycle: The never-ending change of rocks from one type to another
Foliated: Having layers or bands, as in some metamorphic rocks
Crystal: A solid with atoms arranged in a repeating pattern
Fossil: The preserved remains or traces of ancient life
Which rock type usually contains fossils?: Sedimentary
Strata: Layers of sedimentary rock
Law of superposition: In undisturbed layers, the oldest rock is at the bottom
Core sample: A tube of rock or ice pulled from the ground for study
Geologist: A scientist who studies Earth and its rocks
Petrologist: A scientist who studies rocks
Soil: A mix of weathered rock, organic matter, water and air
Humus: Dark, rich decayed plant and animal matter in soil
Topsoil: The top soil layer, rich in nutrients
Bedrock: Solid rock beneath soil
Clay: The smallest soil particles
Silt: Soil particles of medium size
Sand: Soil particles larger than silt and smaller than gravel
Loam: A balanced soil of sand, silt and clay
Frost wedging: Water freezing in cracks and splitting rock
Chemical weathering: Rock changed by chemical reactions, like rusting
Physical (mechanical) weathering: Rock broken into smaller pieces without chemical change
Delta: Sediment fan built where a river meets a larger body of water
Glacier: A large moving mass of ice that carves the land
Rock that forms from lava cooling: Igneous
Rock that forms from heat and pressure on other rocks: Metamorphic
Rock that forms in layers: Sedimentary

Free flashcards from Peabody at peabody.kids/flashcards/earth-rocks