Comprehensive Geology: Rocks, Minerals, and Earth's Processes

What are the three main classes of rocks?

Igneous, Sedimentary, and Metamorphic rocks.

How do cooling rates affect crystal sizes in igneous rocks?

Slower cooling rates allow larger crystals to form, while faster cooling results in smaller crystals.

What are the properties of magma and lava?

Magma is molten rock beneath the Earth's surface, while lava is magma that has reached the surface; both can contain volatiles and vary in viscosity.

What is Bowen's Reaction Series?

A sequence that illustrates the order of mineral crystallization from cooling magma.

What is fractional crystallization?

A process where different minerals crystallize from magma at different temperatures, altering the composition of the remaining liquid.

What is partial melting?

The process where only a portion of a solid is melted, typically occurring in the formation of magma.

What are dikes and sills in geology?

Dikes are vertical intrusions of magma, while sills are horizontal intrusions.

What are plutons?

Large, intrusive igneous rock bodies formed from cooled magma beneath the Earth's surface.

What is the difference between weathering and erosion?

Weathering is the breakdown of rocks, while erosion is the transportation of weathered materials.

What are the formation processes of clastic and chemical sedimentary rocks?

Clastic rocks form from the accumulation of sediment, while chemical rocks form from the precipitation of minerals from solution.

What is foliation in metamorphic rocks?

The alignment of mineral grains under directed pressure, resulting in a layered appearance.

What are the types of metamorphism?

Contact metamorphism, regional metamorphism, and dynamic metamorphism.

What are polymorphs of kyanite?

Different structural forms of kyanite that occur under varying temperature and pressure conditions, indicating metamorphic conditions.

What are metamorphic facies?

Sets of metamorphic mineral assemblages formed under specific temperature and pressure conditions.

What are common protoliths in metamorphic rocks?

Common protoliths include shale (to slate), granite (to gneiss), and limestone (to marble).

What is the significance of the geologic time scale?

It provides a framework for understanding Earth's history and the timing of geological events.

What occurs at a rift boundary?

Plates diverge, causing the crust to thin and tear.

What happens at a convergent boundary?

Two or more plates move toward each other, destroying crust and potentially building mountains.

What is a subduction zone?

A region where dense oceanic lithosphere slides under lighter continental lithosphere, forming trenches and volcanic chains.

What are Benioff Zones?

Dipping zones of increased earthquake activity produced within a plate of oceanic lithosphere as it is subducted.

What is the result of ocean crust meeting ocean crust at a subduction zone?

It forms volcanic island arcs.

What is the primary characteristic of transform boundaries?

Plates slide past one another, such as the San Andreas Fault in California.

Why is it important to study rocks?

Understanding their physical properties helps determine suitability for construction, foundations, and records geological history.

What is a rock?

A coherent and naturally occurring solid, consisting of an aggregate of minerals or mineraloids.

What are the two textures of rocks?

Clastic and crystalline.

What holds clastic rocks together?

Cement, which is a natural mineral material that fills the space between grains.

What are the three broad classes of rocks?

Igneous, sedimentary, and metamorphic.

How are igneous rocks formed?

They are formed as magma cools and crystallizes.

What is lithification?

The process of turning sediments into rock through compaction and cementation.

What distinguishes sedimentary rocks?

They can form from compacted sediments or from crystals precipitating out of a solution.

What characterizes metamorphic rocks?

They are formed when pre-existing rock is altered by intense heat and/or pressure.

What is the rock cycle?

A process where rocks of any type can be transformed into any other type through various geologic processes.

What are plutonic and volcanic rocks?

Plutonic rocks cool slowly underground (e.g., granite), while volcanic rocks cool quickly at or near the surface (e.g., basalt).

What is a mineral?

A naturally occurring solid with a definite chemical composition and crystalline structure.

What is an isotope?

An atom of the same element with a different number of neutrons, resulting in a different atomic mass.

What are ions?

Atoms with a net positive or negative charge due to the loss or gain of electrons.

What is a crystal?

A solid with atoms arranged in a highly ordered structure, forming a crystal lattice.

What are polymorphs?

Minerals with the same chemical composition but different crystal structures, leading to different physical properties.

What are the two fundamental characteristics of minerals?

Crystal structure and chemical composition.

What is the significance of the Mohs scale?

It measures the hardness of minerals.

What is cleavage in minerals?

The way a mineral breaks along specific planes of weakness.

What is the definition of crystalline structure?

An orderly arrangement of atoms in a mineral.

What are the main processes of mineral formation?

Solidification of a melt, precipitation from a solution, diffusion through a solid, metabolism of organisms, precipitation from a gas, and nucleation.

What is a unit cell in mineralogy?

The smallest unit of volume that can be stacked to fill all space.

What is the significance of the silica tetrahedron?

It is the building block of silicate minerals, consisting of a silicon ion surrounded by four oxygen ions.

What are the two main groups of minerals based on silica content?

Silicates (containing SiO4) and Non-silicates (not containing SiO4).

What are the characteristics of isolated silicates?

They include ferromagnesian minerals like olivine and have a structure that allows for easy weathering.

What defines sheet silicates?

They have a structure of stacked sheets that can easily split, including minerals like clay and micas.

What are framework silicates?

Silicates like quartz and feldspar that have a weather-resistant structure.

What are carbonates and their common examples?

Minerals that contain CO2, such as calcite (CaCO3) and dolomite (MgCaCO3).

What are sulfates and their significance?

Minerals containing SO4, useful for building materials, with examples like gypsum (CaSO4).

What are the characteristics of sulfides?

They consist of a metal combined with sulfur and are hosts for many metallic ores.

What is the difference between magma and lava?

Magma is molten rock underground, while lava is molten rock that reaches the Earth's surface.

What are extrusive igneous rocks?

Rocks that form from lava cooling above ground.

What are intrusive igneous rocks?

Rocks that form from magma cooling below ground.

What are the two main sources of Earth's heat?

Leftover heat from formation and the decay of radioactive elements.

What causes magma formation?

Decompression melting, addition of volatiles, and heat transfer.

What is decompression melting?

The process where pressure reduction allows hot rocks to melt.

What role do volatiles play in magma formation?

They lower the melting temperature of rocks, facilitating flux melting.

What is the Bowen's Reaction Series?

A sequence that describes the order in which minerals crystallize from a cooling melt.

What is assimilation in magma formation?

The incorporation of surrounding wall rocks into rising magma, resulting in a uniform mixture.

What factors influence magma viscosity?

Silica content, temperature, and the presence of volatiles.

What is the difference between dry and wet melts?

Dry melts contain few to no volatiles, while wet melts can contain up to 15% volatiles.

What is the significance of partial melting?

It allows for the formation of silica-rich magma from only a portion of a rock melting.

What does magma mixing refer to?

The blending of different magmas in a magma chamber, resulting in a new composition.

What is the role of differentiation in magma cooling?

It describes how minerals crystallize at different temperatures, leading to varying rock compositions.

What is the relationship between volatile content and viscosity in magma?

More volatiles result in lower viscosity.

What are the two main types of igneous environments?

Extrusive and Intrusive.

Describe a mellow eruption style.

Low-viscosity lava (basalt) exits volcano vents and can flow long distances as sheets.

What characterizes extrusive igneous settings?

They have high viscosity melts and volatiles, leading to explosive eruptions that eject large clouds of ash and debris.

What are Large Igneous Provinces (LIPs)?

Unusually large outpourings of magma that can flow hundreds of kilometers and accumulate in thick piles.

What is a tabular intrusion?

A roughly planar intrusion with a uniform thickness, ranging from centimeters to hundreds of meters.

What is the difference between a dike and a sill?

A dike cuts across pre-existing layers, while a sill is injected parallel to the rock layers.

How do dikes form?

They form in regions where the crust is stretched horizontally, such as during rifting and sea-floor spreading.

Where do sills typically form?

Near the Earth's surface, where magma can push the underlying rock upward.

What is a laccolith?

A blister-shaped intrusion that forms when magma pushes up the overlying rock.

What is a batholith?

A group of plutons that are several hundred kilometers long and represent the largest igneous intrusions.

What factors affect the cooling rate of igneous intrusions?

Large spherical bodies cool slowly, while tabular-shaped intrusions cool quicker.

What is an aphanitic texture?

A fine-grained texture resulting from rapid cooling, where crystals do not have time to grow.

What is a phaneritic texture?

A coarse-grained texture resulting from slow cooling, allowing crystals to grow larger.

What does a porphyritic texture indicate?

A mixture of coarse and fine crystals, indicating a two-stage cooling history.

What is a glassy texture in igneous rocks?

A solid mass of glass or crystals surrounded by glass, resulting from rapid cooling.

What are the main classifications of igneous rocks based on composition?

Felsic, intermediate, mafic, and ultramafic.

Where does most igneous activity occur?

At tectonic plate boundaries.

What is a volcanic arc?

A region marking convergent tectonic plates at some boundaries.

What type of magma is typically erupted at oceanic hot spots?

Mostly mafic magma (basalt).

What occurs during continental rifting?

Decompression melting of mafic rocks and heat transfer that melts the crust.

What is the primary igneous activity at mid-ocean ridges?

Rifting spreads plates leading to decompression melting, with basaltic magma filling magma chambers.

What are siliciclastic sediments?

Sediments created by the weathering of common rocks composed largely of silicate minerals.

How are chemical sediments formed?

They form at or near their place of deposition.

What are biological sediments?

Sediments that form at or near their place of deposition as a result of mineral precipitation by organisms.

What are clastic sedimentary rocks composed of?

Cemented mineral grains and/or rock fragments.

What are the three types of weathering?

Physical, chemical, and biological.

What is physical weathering?

The mechanical breakdown of rocks at the surface by processes such as freezing/thawing and tree roots.

What is chemical weathering?

The process where minerals and rocks are chemically altered or dissolved.

What is erosion?

The process by which sediments are worn away and moved elsewhere by gravity or a moving transport agent.

What does the kinetic energy formula K = 1/2 m v² represent?

It represents the kinetic energy of an object, where m is mass and v is velocity.

What is burial in the context of sedimentary rocks?

The preservation of sediments within a sedimentary basin.

What is diagenesis?

The physical and chemical change that converts sediments to sedimentary rocks.

What factors are used to classify clastic rocks?

Grain size, composition, angularity/sphericity, sorting, sediment maturity, and character of cement.