Glossary

accommodation space

the space that is available for the deposition of sediments. In river systems, changes in accommodation are controlled by the river gradient, water discharge rates and sediment supply.

accretionary prism

a mass of sedimentary material scraped off of oceanic crust during subduction that piles up at the edge of the overriding plate

barren

a landscape that lacks plant or animal life

Barrovian sequence

a series of metamorphic zones with both pressure and temperature increase generally due to continental collision

bathymetry

the depth of water in oceans, seas, or lakes

beds

distinct layers of sediment that have a thickness greater than 1 cm

bottom simulating reflector

a seismic reflection occurring in the upper few hundred meters of marine sediments mimicking the seafloor

bryozoan

a type of aquatic invertebrate animals. They are filter feeders that extract food particles out of the water using tentacles.

burial

process in which sedimentary layers are piled up and the sediments beneath are buried, sometimes by hundreds of meters of sediment above

calcite

a carbonate mineral, CaCO3. This is the stable polymorph at the Earth's surface

cementation

process of transforming clastic sediments into rocks by the precipitation of mineral matter in their pore spaces

chemical sedimentary rock

form when minerals in solution become supersaturated and inorganically precipitate

clast

a fragment of geological detritus broken off other rocks by physical weathering

clastic

sedimentary rocks composed of broken pieces of older rocks

clinoforms

these sedimentary layers are timelines that represent a moment in geological time

contacts

a boundary which separates one rock body from another. These can be depositional, unconformable, and intrusive contacts

continental drift

the hypothesis proposed by Alfred Wegener in 1915 that stated the continents were moving

convergent

a plate boundary where two plates move towards each other

costa (plural = costae)

Rib or rib-like structures

divergent

a linear feature where two plate boundaries move apart from each other

divergent plate boundary

a linear feature where two plates move away from each other

eon

longest division of geological time, subdivided into eras

evaporite

a type of sediment that consists of water-soluble minerals deposited after concentration and crystallization by evaporation from an aqueous solution

extrusive

igneous rocks that form when magma cools at or near the Earth's surface

fault

a fracture or zone of fractures between two pieces of rock

felsic

an igneous rock rich in feldspar (fel) and quartz (si)

foliation

planar arrangement of structural or textural features in metamorphic rocks along straight or wavy planes

foreland basin

structural basin that develops adjacent and parallel to a mountain belt formed from the mass created by crustal thickening that causes the lithosphere to bend creating accommodation space

geologic time scale

a system that geologists use to relate chronological dating to geological strata (stratigraphy)

geophones

a device that converts ground movement (velocity) into voltage, which is recorded as a seismic response and is analyzed for structure of the earth.

geothermal gradient

change in temperature with respect to increasing depth. Away from the edges of lithospheric plates, it is about 25–30 °C/km

gneiss

a metamorphic rock made up of bands that differ in color and composition; generally there are light-colored bands rich in feldspar and quartz and dark-colored bands rich in mafic minerals such as biotite or amphibole

granite

a coarse-grained, intrusive igneous rock typically composed of quartz, feldspars, and amphibole/biotite.

hardness

measure of the resistance to scratching by another object or mineral

hotspots

linear volcanic regions that are probably fed by underlying mantle that is anomalously hot compared with the surrounding mantle

igneous dike

a sheetlike igneous body that is often oriented vertically or steeply inclined to the bedding or layering

intrusive

an igneous rock that forms when magmas cool beneath the Earth's surface

Jurassic

a geologic period that spanned 56 million years from the end of the Triassic Period 201.3 Ma to the beginning of the Cretaceous Period 145 Ma. This constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles

laminations

distinct layers of sediment that have a thickness less than 1 cm

landscape

visible features of an area of land and its landforms

lithification

process where loose grains of sediment are converted into rock, often by cementation

lithosphere

the uppermost layer of the Earth as defined by physical properties. It is composed of the crust and uppermost, rigid part of the mantle.

luster

how light interacts with the surface of a mineral

mafic

an igneous rock that is rich in magnesium (ma) and iron (f), often has abundant pyroxene, olivine and amphibole

magma

molten matter beneath or within the Earth's crust from which igneous rocks are formed

mantle

a layer in the Earth or a planet that is between the core and crust

Mercator projections

a map projection of the world on to a cylinder so that all the latitude lines have the same length as the equator

Mesozoic

interval of geological time from 252 to 66 million years ago. Some call it the Age of Reptiles or the Age of Conifers. The Mesozoic is one of three geologic eras of the Phanerozoic Eon, between the Paleozoic and the Cenozoic

metamorphic rocks

the process by which heat, pressure or fluids transform the minerals and textures of the rock

mid-ocean ridge

an underwater mountain and rift system formed by an oceanic divergent plate boundary

migmatite

heterogeneous rock with properties of both igneous and metamorphic rocks; often formed by partial melting

mineral

a naturally occurring, inorganic, solid that can be defined by a chemical formula and a crystal structure.

mountain belts

an aligned group of mountain ranges that form from the same cause, usually an orogeny or convergent plate boundary

onlap

pattern of reflections in seismic data that occur during periods of transgression (sea level rise)

ophiolite

a section of oceanic crust and its underlying upper mantle that has been uplifted and exposed, generally now on continental crust

organic sedimentary rocks

form from the accumulation and lithification of organic matter, such as leaves and other plant or animal material

orogeny

a mountain-building event typically resulting from a convergent tectonic boundary.

paleoclimate

the climate during some past geological time

Paleozoic

the earliest of three geologic eras of the Phanerozoic Eon. It is the longest of the Phanerozoic eras, lasting from 541 to 252 million years ago

Pangea

an ancient landmass of almost all of the continental crust or supercontinent that formed in the late Paleozoic

Panthalassan

a super ocean that surrounded all of the supercontinent Pangea

Permian

a geologic period that spans 47 million years at the end of the Paleozoic era, from the end of the Carboniferous period (298.9 Ma) to the beginning of the Mesozoic era with Triassic period (251.902 Ma)

plate boundaries

the edge of either a continental or oceanic tectonic plate

polymorph

two or more minerals that have the same chemical composition but differ in their internal atomic arrangement and crystal structure

polymorphism

a solid material that exists in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including minerals, polymers, and metals

porphyroblast

a large mineral in a metamorphic rock which has grown in the fine grained matrix

protolith

original, unmetamorphosed rock from which a metamorphic rock was formed; sometimes called the parent rock

pull-apart basin

a basin formed between two adjacent strike-slip faults in a region where subsidence generates accommodation space for the deposition of sediments

pyrite

metallic, yellow mineral made of FeS2 and typically occurring as intersecting cubes. Often called Fool's Gold

quartz

mineral consisting of SiO2, silicon dioxide, found in all rock types, the stable polymorph at the Earth's surface

reflector

a seismic reflector may represent a change in lithology, a fault or an unconformity

rock cycle

a concept in geology that describes transitions among the three main rock types: sedimentary, metamorphic, and igneous

sandstone

a clastic sedimentary rock composed of sand-sized minerals, rock fragments or organic material

sponge

multicellular organisms with bodies full of pores allowing water to circulate through them. They are made of collagen and some have silica-rich spicules.

stratigraphic column

a representation used to describe the vertical sequence of rock units

stratigraphic section

a sequence of rock layers or formations in the order they were deposited

streak

color of a mineral in a powdered form

subduction

a process that occurs at convergent plate boundaries where one plate descends beneath another into Earth's mantle.

suture

the zone where two plates meet during continent-continent collision

suturing

the zone where two continental plates meet during convergence

symmetrical ripple marks

a sedimentary structure produced by the back-and-forth motion of waves or tides in which both limbs of the ripple are at about the same angle

ternary plots

a graph that depicts the ratios of the three variables as positions in an equilateral triangle

transform

a plate boundary where two plate boundaries move horizontally beside each other

trench

a topographic depression of the sea floor, relatively narrow in width, but very long usually associated with convergent plate boundaries

Triassic

a geologic period that spans 50.6 million years from the end of the Permian Period 251.9 Ma, to the beginning of the Jurassic Period 201.3 Ma. This is the first and shortest period of the Mesozoic Era

unconformity

a buried erosional or non-depositional surface separating two rocks or strata of different ages, indicating that sediment deposition was not continuous

uniformitarianism

the theory that the same natural laws and processes that operate in our present-day scientific observations have always operated in the universe in the past and apply everywhere in the universe. It is sometimes referenced as "The present is the key to the past".

volcanic ash

fragments of rock, minerals, and volcanic glass, created during volcanic eruptions and measuring less than 2 mm in diameter

volcanic material

larger fragments of rock, minerals, and volcanic glass created during volcanic eruptions and measuring more than 2 mm in diameter

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The Story of Earth by Daniel Hauptvogel & Virginia Sisson is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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