Understanding Geosphere Materials and Rock Types

rock

a solid part of the geosphere that is mostly an aggregate of one or more minerals

mineral

a naturally occurring inorganic solid made up of an element or a combination of elements that has an ordered arrangement of atoms

sedimentary

a type of rock formed by the accumulation of sediments

igneous

a type of rock formed from the cooling and solidification of magma or lava

crystal

a solid in which the atoms are arranged in a highly ordered, repeating pattern

bedding

the layering that occurs in sedimentary rocks

mafic

describes a silicate mineral or rock that is rich in magnesium and iron

cleavage

a weak plane in a mineral's structure, along which it will break

weathering

the process of breaking down rocks and minerals through natural processes

differentiation

the process by which different minerals crystallize from magma at different temperatures

silicate mineral

a mineral that includes silicon and oxygen tetrahedra in its internal structure

erosion

the process by which soil and rock are removed from the Earth's surface by natural processes

felsic

describes a silicate mineral or rock that is rich in feldspar and silica

clay

a fine-grained natural rock or soil material that combines one or more minerals

clastic

a type of sedimentary rock composed of fragments of pre-existing rocks and minerals

plutonic

describes igneous rocks that solidify below the Earth's surface

ferromagnesian

describes silicate minerals that contain iron and magnesium

lithified

the process by which sediments compact under pressure and gradually become solid rock

volcanic

describes igneous rocks that solidify at the Earth's surface

metamorphic

a type of rock that has been changed by heat, pressure, or chemically active fluids

rock cycle

the continuous process by which rocks are created, altered, destroyed, and reformed

foliation

the repetitive layering in metamorphic rocks

atom

particle made up of a nucleus of positively charged protons and neutral neutrons surrounded by negatively charged electrons

element

a substance that can't be broken down into other substances, made of one kind of atom

density

the mass per unit volume of a substance

silicosis

a lung disease caused by inhaling tiny particles of quartz, leading to inflammation and nodular lesions

feldspar

a group of silicate minerals that contain silica, aluminum, potassium, sodium, and calcium

quartz

a common mineral composed of silicon dioxide (SiO2) with a hardness of 7 on Moh's scale

Feldspar weathering

The process by which feldspar minerals change into more stable minerals due to lower temperatures and pressures at Earth's surface.

Chemical Weathering

The process that involves the chemical alteration of minerals, often through reactions with water and other substances.

Physical Weathering

The process that involves the mechanical breakdown of minerals without changing their chemical composition.

Hydrolysis

A reaction of water (H2O) with minerals to form new minerals, many of which contain water in their atomic structures.

Dissolution

A process where chemical (atomic) constituents of minerals are dissolved and removed.

Clays

A group of water-containing aluminum silicate minerals that have a layered structure.

Micas

Silicate minerals whose internal structures include a plane with very weak bonds, allowing them to easily break into sheets.

Biotite

A dark mica that is an iron-bearing mineral.

Muscovite

A silvery mica that is potassium-rich.

Ferromagnesian Minerals

Silicate minerals that contain abundant iron or magnesium in their internal structure.

Olivine

A ferromagnesian mineral with the formula (Mg, Fe)2SiO4, greenish color, hardness of 6, and a conchoidal fracture.

Pyroxene

A ferromagnesian mineral with the formula (Mg, Fe, Ca)2 Si2O6, dark color, hardness of 6, and short rectangular prisms.

Chrysotile

An elongate, fibrous serpentine mineral that is the principal mineral in asbestos, known for being heat-resistant and flexible.

Tremolite

A dangerous asbestiform amphibole that has caused serious health problems.

Biotite Formula

K(Mg,Fe)3(Al,SiO3010)(OH)2, a hydrated black mineral with a hardness of 3 and moderate density.

Hornblende

A dark mineral with the formula (Ca,Na)2-3(Mg,Fe,Al)5 Si6(Si,Al)2O22(OH)2O6, hardness of 5-6, and two cleavages at 56 and 124 degrees.

Sulfides

Combinations of ions, especially metals with positive charges, with sulfur (2- charge).

Lead Sulfide

PbS, a type of sulfide mineral also known as galena.

Pyrite

FeS2, also known as 'Fool's Gold,' a type of sulfide mineral.

Zinc Sulfide

ZnS, a type of sulfide mineral known as sphalerite.

Oxides

Combinations of ions, especially metals with positive charges, with oxygen (2- charge).

Titanium Oxide

TiO2, a type of oxide mineral known as rutile.

Iron Oxides

Fe3O4, a type of oxide mineral known as magnetite.

Hematite

Fe2O3, an iron oxide that gives rocks and soils a rusty color.

Goethite

FeO(OH), another iron oxide mineral.

Oxidation

A chemical reaction where positive ions in minerals combine with oxygen.

Rust

An example of oxidation, specifically the combination of hematite and goethite.

Carbonates

Combinations of positively charged ions (Ca2+, Mg2+, Fe2+) with negatively charged carbonate (CO3).

Calcite

A carbonate mineral with the formula CaCO3.

Dolomite

A carbonate mineral with the formula (Ca,Mg)CO3.

Karst Terrains

Landscapes underlain by calcite-rich rocks that show many dissolution features.

Rock

A solid part of the geosphere that is most commonly an aggregate of one or more minerals.

Igneous Rock

A rock formed from molten material.

Sedimentary Rock

A rock that is formed from either clastic (pieces) or chemical sediments.

Metamorphic Rock

A rock that has changed in response to high temperature and pressure.

Granite

An aggregate of quartz, potassium feldspar, plagioclase feldspar, and biotite.

Limestone

A sedimentary rock consisting mainly of calcite.

Dissolution

The process that leads to the formation of caves, hummocky landscapes, and sinkholes.

Felsic

Igneous rocks with abundant quartz and feldspar, typically light colored.

Mafic

Igneous rocks with abundant ferromagnesian minerals, typically dark colored.

Intermediate

Igneous rocks common in subduction zones with 55-63% SiO2.

Phaneritic

Texture of igneous rocks with coarse grains visible to the eye.

Aphanitic

Texture of igneous rocks with fine crystals that need magnification to be seen.

Plutonic Igneous Rocks

Rocks that crystallized from magma within the crust.

Volcanic Igneous Rocks

Rocks formed from lava erupted from a volcano.

Glassy Texture

A texture seen in obsidian.

Vesicular Texture

A texture characterized by holes, seen in pumice.

Basalt

An aphanitic igneous rock that is typically dark colored.

Gabbro

A phaneritic igneous rock that is coarser-grained than basalt.

Rhyolite

An aphanitic igneous rock that is typically light colored.

Oceanic crust

Includes deep-sea sediments, basalt lava flows, sheeted basalt dikes, gabbro intrusions, and some ultramafic rocks.

Continental crust

More compositionally diverse than oceanic crust, ranging from mafic to felsic, with an average composition that is intermediate between these two end members.

Differentiation

The process where the composition of magma changes through physical separation of early crystallized minerals.

Melting

Produces intermediate compositions.

Oceanic crust alteration

Altered by hydrolysis with seawater and recrystallization during subduction, which releases H2O, melting the crust.

Andesite

An intermediate rock type between felsic and mafic composition, with magmas characteristic of subduction zones.

Explosive magmas

Often release volatiles such as H2O, CO2, and H2S.

Weathering

A set of physical and chemical processes that change rocks at Earth's surface.

Uplift

Causes rocks to be exposed as outcrops on Earth's surface.

Physical weathering

Breaks the rocks into smaller pieces with a higher surface area to volume ratio.

Frost wedging

The repeated expansion of water as it freezes in cracks, disaggregating rocks.

Root wedging

Growth of plant roots in cracks that breaks rocks apart.

Chemical weathering

Processes such as hydrolysis, oxidation, and dissolution that decompose rocks.

Erosion

Transportation of geosphere materials by movements of water, wind, and ice (glaciers).

Glaciers

Scrape material off valleys as they flow downslope and push material in front as they advance.

Moraines

Deposits of rock debris from glaciers.

Bedload

Rock material rolled and bounced along the bottom of a stream/river.

Clastic sediments

Composed of fragments of material.

Chemical sediments

Precipitate from solutions.

Sedimentation

The depositing of sediment.

Lithification

The changing of sediment into solid rock.

Sedimentary basin

A large area where sediment accumulates.