Terms

Earth’s Layers & Atomic Structure

• Crust – The outermost solid layer of Earth, composed mostly of silicate minerals.

• Mantle – The layer beneath the crust, made of solid and partially molten rock, rich in magnesium and iron.

• Core – The innermost part of Earth, composed mostly of iron and nickel, divided into a solid inner core and a liquid outer core.

• Silica Tetrahedron – The basic building block of silicate minerals, consisting of one silicon atom bonded to four oxygen atoms.

• Atom – The smallest unit of an element that retains its chemical properties.

• Atomic Mass Number – The sum of protons and neutrons in an atom's nucleus.

• Atomic Number – The number of protons in an atom’s nucleus, determining the element.

• Atomic Weight – The weighted average mass of an element’s isotopes.

Minerals & Their Properties

• Chain Silicate Structure – A silicate structure where silica tetrahedra are linked in chains.

• Cleavage – The tendency of a mineral to break along specific planes due to its atomic structure.

• Crystal Form – The external shape of a mineral that reflects its internal atomic structure.

• Density – Mass per unit volume of a substance (g/cm³ for minerals).

• Luster – The way a mineral reflects light, such as metallic or non-metallic.

• Element – A pure substance consisting of one type of atom.

• Electron – A negatively charged subatomic particle found in atoms.

• Feldspar Group – A group of silicate minerals that make up a large portion of Earth's crust.

• Hardness – A mineral’s resistance to scratching, measured by Mohs hardness scale.

• Ion – An atom or molecule with a net electric charge due to the loss or gain of electrons.

• Sheet Silicate Structure – A silicate structure where silica tetrahedra form continuous sheets.

• Mineral – A naturally occurring, inorganic solid with a definite chemical composition and crystalline structure.

• Neutron – A neutrally charged subatomic particle found in an atom's nucleus.

• Nucleus – The central part of an atom, containing protons and neutrons.

• Proton – A positively charged subatomic particle found in an atom’s nucleus.

• Pyroxene – A group of silicate minerals commonly found in igneous and metamorphic rocks.

• Silicates – Minerals containing silicon and oxygen, often combined with other elements.

• Streak – The color of a mineral's powdered form when scratched against a streak plate.

Igneous Rocks & Processes

• Basalt – A fine-grained, dark-colored, mafic volcanic rock.

• Batholith – A large mass of intrusive igneous rock that solidified deep within Earth’s crust.

• Bowen’s Reaction Series – A model that explains the sequence of mineral crystallization from magma.

• Coarse-Grained – A texture in igneous rocks where crystals are large and visible.

• Dike – A vertical or near-vertical igneous intrusion that cuts across rock layers.

• Fine-Grained – A texture in igneous rocks where crystals are small and not easily visible.

• Gabbro – A coarse-grained, dark-colored, mafic intrusive igneous rock.

• Granite – A coarse-grained, felsic intrusive igneous rock.

• Extrusive Rock – Igneous rock that forms from lava cooling on Earth’s surface.

• Igneous Rock – Rock formed from the cooling and solidification of magma or lava.

• Intermediate Rock/Magma – Rock or magma with a composition between mafic and felsic.

• Intrusion – The process of magma entering and solidifying within pre-existing rocks.

• Lava – Molten rock that has erupted onto Earth’s surface.

• Mafic Rock/Magma – Dark-colored, magnesium- and iron-rich igneous rock/magma.

• Magma – Molten rock beneath Earth’s surface.

• Mantle Plume (Hot Spot) – An upwelling of hot rock from the mantle that forms volcanoes.

• Pluton – A body of intrusive igneous rock that solidified underground.

• Rhyolite – A fine-grained, felsic volcanic rock.

• Rock Cycle – The continuous transformation of rocks through geological processes.

• Felsic (Silicic) Rock/Magma – Light-colored, silica-rich igneous rock/magma.

• Sill – A horizontal igneous intrusion between rock layers.

• Xenolith – A piece of foreign rock embedded in igneous rock.

Volcanic Features & Eruptions

• Caldera – A large crater formed when a volcano collapses.

• Cinder Cone – A small, steep-sided volcano made of volcanic debris.

• Composite Volcano – A volcano with alternating layers of lava and pyroclastic material.

• Obsidian – A glassy volcanic rock formed from rapidly cooled lava.

• Porphyritic – A rock texture with large crystals in a fine-grained matrix.

• Pahoehoe – Smooth, ropy lava.

• Aa – Rough, jagged lava.

• Pumice – A light, porous volcanic rock formed by rapid cooling of gas-rich lava.

• Pyroclastic Flow – A fast-moving, hot cloud of volcanic ash, gas, and debris.

• Shield Volcano – A broad, gently sloping volcano formed by low-viscosity lava.

• Vesicle (Vesicular) – A small cavity in volcanic rock formed by trapped gas bubbles.

• Viscosity – A fluid’s resistance to flow; in lava, it determines eruption style.

Weathering & Sedimentary Rocks

• Chemical Weathering – The breakdown of rocks by chemical reactions.

• Clay Mineral – A fine-grained mineral that forms from weathered silicates.

• Exfoliation Dome – A rock formation created by pressure release and peeling layers.

• Frost Wedging – The mechanical breaking of rock due to freeze-thaw cycles.

• Hematite – An iron oxide mineral, often forming rust-colored weathering.

• Mechanical Weathering – The physical breakdown of rocks into smaller pieces.

• Chert – A hard, silica-rich sedimentary rock.

• Bedding – Layers of sedimentary rock.

• Cementation – The process of minerals binding sediment

• Chemical Sedimentary Rocks – Rocks formed from minerals precipitating from a solution, such as limestone and evaporites.

• Clastic Sedimentary Rocks – Rocks composed of fragments of pre-existing rocks that have been compacted and cemented together.

• Compaction – The process by which sediments are pressed together under pressure, reducing pore space and increasing density.

• Clay – The finest-grained sedimentary particle, less than 0.004 mm in diameter.

• Coal – A sedimentary rock formed from compacted plant material, rich in carbon.

• Conglomerate – A coarse-grained clastic sedimentary rock composed of rounded gravel-sized particles.

• Cross-Bedding – Layers in sedimentary rocks that are inclined at an angle to the main bedding, indicating past environments like dunes or river channels.

• Evaporite – A type of chemical sedimentary rock formed from minerals left behind after water evaporates, such as rock salt (halite).

• Fossil – The preserved remains or traces of ancient organisms found in sedimentary rocks.

• Gravel – Loose rock fragments that are coarser than sand, typically larger than 2 mm in diameter.

• Limestone – A sedimentary rock primarily composed of calcium carbonate (CaCO₃), often formed from marine organisms' shells.

• Lithification – The process of turning loose sediments into solid rock through compaction and cementation.

• Mud Cracks – Polygonal cracks that form when wet mud dries and contracts, later preserved in sedimentary rocks.

• Pore Space – The open spaces between sediment grains that can hold water, air, or hydrocarbons.

• Ripple Marks – Small ridges formed on sediment surfaces by water or wind movement, often preserved in sedimentary rocks.

• Sand – A sedimentary particle between 0.0625 and 2 mm in diameter, commonly composed of quartz.

• Sandstone – A clastic sedimentary rock composed mostly of sand-sized mineral grains.

• Sedimentary Structure – Features in sedimentary rocks, such as bedding, ripple marks, or mud cracks, that provide clues about past environments.

• Shale – A fine-grained clastic sedimentary rock composed mostly of clay-sized particles, known for its ability to split into thin layers.

• Silt – A sediment particle smaller than sand but larger than clay, between 0.004 and 0.0625 mm in diameter.

• Environment of Deposition – The setting where sediments accumulate, such as a river, ocean, or desert.

Metamorphic Rocks & Processes

• Contact Metamorphism – When rocks change due to heat from nearby magma, but without melting.

• Foliation – A layered or banded texture in metamorphic rocks caused by pressure.

• Gneiss – A high-grade metamorphic rock with distinct light and dark bands.

• Hydrothermal Metamorphism – When hot, mineral-rich water changes a rock’s minerals.

• Marble – A metamorphic rock formed from limestone, often used in sculptures.

• Metamorphic Grade – A measure of how much heat and pressure a rock has experienced.

• Parent Rock – The original rock before it was changed by metamorphism.

• Quartzite – A hard metamorphic rock formed from sandstone, mainly composed of quartz.

• Regional Metamorphism – Large-scale rock changes due to intense heat and pressure over big areas.

• Schist – A shiny, flaky metamorphic rock with visible mineral grains.

• Slate – A fine-grained, layered metamorphic rock used for roofing and chalkboards.