Geol 2 - Study Guide for Exam 1: Minerals, Igneous Rocks, Weathering & Erosion, Sedimentary Rocks

Vocabulary flashcards generated from the Geol 2 Exam 1 study guide covering minerals, igneous rocks, weathering, erosion, and sedimentary rocks.

Mineral

A naturally occurring, inorganic solid with a crystalline structure and a definable chemical formula.

Silicates

The most abundant mineral group in Earth's crust, characterized by silicon-oxygen tetrahedra.

Silica Tetrahedron

The fundamental building block of silicate minerals, composed of one central silicon atom bonded to four oxygen atoms.

Polymorph

Minerals that share identical chemical compositions (such as pure carbon in diamond and graphite) but possess different crystal structures and physical properties.

Mohs Scale

A relative scale used to measure the scratch resistance and hardness of minerals.

Eight Major Rock-Forming Elements

The most common elements forming Earth's crustal rocks: Oxygen ($\text{O}$), Silicon ($\text{Si}$), Aluminum ($\text{Al}$), Iron ($\text{Fe}$), Calcium ($\text{Ca}$), Sodium ($\text{Na}$), Potassium ($\text{K}$), and Magnesium ($\text{Mg}$).

Bowen's Reaction Series

A schematic sequence depicting the specific order in which different silicate minerals crystallize from a cooling magma along continuous and discontinuous branches.

Fractional Crystallization

The process by which earlier-formed crystals separate from a cooling melt, altering the chemical composition of the remaining magma over time.

Magma

Molten rock generated beneath the surface of the Earth.

Lava

Molten rock that reaches and flows onto the Earth's surface.

Partial Melting

The incomplete melting of parent rock, yielding a melt enriched in silica compared to the original rock composition.

Decompression Melting

Melting triggered when hot mantle material ascends to shallower depths with lower pressure without gaining extra heat.

Flux Melting

Melting initiated when volatile substances (such as water) lower the melting temperature of hot mantle rock.

Pluton

An intrusive igneous structure formed when magma cools and crystallizes underground.

Dikes and Sills

Tabular intrusive igneous bodies; dikes cut vertically or diagonally across pre-existing rock layers (a), whereas sills intrude horizontally parallel to the rock layers (b).

Xenolith

A piece of surrounding country rock that becomes enveloped inside an igneous melt without melting completely.

Felsic Igneous Rock

Silica-rich, light-colored igneous rock composed primarily of quartz and feldspars, having lower density.

Mafic Igneous Rock

Iron- and magnesium-rich, dark-colored igneous rock with high density and lower silica content.

Ultramafic Rock

An igneous rock with extremely high magnesium and iron content and low silica content, forming at the highest solidification temperatures.

Obsidian

A dark, glassy volcanic rock produced by extremely rapid cooling of lava, preventing crystal formation.

Physical Weathering

The mechanical breakdown of rock into smaller pieces without altering its chemical composition.

Chemical Weathering

The alteration or breakdown of rock minerals through chemical reactions such as dissolution, oxidation, and hydrolysis.

Exfoliation

A mechanical weathering process in which concentric slabs or sheets of rock break off parallel to the exposed rock surface.

Spheroidal Weathering

A chemical weathering phenomenon that rounds off angular edges and sharp corners of jointed rock blocks.

Differential Weathering

Un-even weathering that occurs at varying rates across different rock bodies due to variations in mineral resistance and structural joints.

Weathering Rind

An outer layer of chemically altered rock material encasing an unweathered core.

Regolith

The loose layer of unconsolidated rock debris and soil overlying intact bedrock.

Sediment

Unconsolidated, loose particles generated by mechanical and chemical weathering or precipitated directly from aqueous solution.

Lithification

The process converting loose sediment into solid rock through compaction under pressure and mineral cementation.

Mature Sediment

Sediment that has undergone extensive transport, resulting in well-sorted, well-rounded grains dominated by stable minerals like quartz.

Sorting

The degree of uniformity in particle sizes within sedimentary debris, reflecting the energy and environment of transport.

Clastic Sedimentary Rock

Sedimentary rock created from cemented solid fragments (clasts) derived from pre-existing rocks.

Biochemical Sedimentary Rock

Sedimentary rock constructed from the hard skeletal remains or shells of marine organisms.

Organic Sedimentary Rock

Sedimentary rock consisting of compacted, carbon-rich plant matter, such as coal.

Chemical Sedimentary Rock

Sedimentary rock formed by direct chemical precipitation of minerals out of dissolved water solutions.

Evaporite

A chemical sedimentary rock formed when salt-saturated water evaporates, leaving mineral precipitates like halite or gypsum behind.