Definitions Flashcards
Abyssal plain
A broad, relatively flat region of th ocean that lies at least 4.5 km below sea level
Amber
Hardened (fossilised) ancient sap or resin
Angular unconformity
An unconformity in which the strata below were tilted or folded before the unconformity developed; strata below the unconformity therefore have a different tilt than strata above
Asteroid
One of the fragments of solid material, left over from planet formation or produced by collision of planetesimals, that resides between the orbits of Mars and Jupiter
Asthenosphere
The layer of the mantle that lies between 100-150km and 300km keep; is relatively soft and can flow when acted on by force
Astronomical unit
The distance between the Sun and the Earth, used as a reference frame for describing distances among objects in our Solar System
Atmosphere
A layer of gases that surrounds a planet
Atom
The smallest piece of an element that has the properties of the element; It consists of a nucleus surrounded by an electron cloud
Atomic mass
The amount of matter in an atom
Bathymetry
Variation in depth
Big Bang Theory
A cataclysmic explosion represents the formation of the Universe; before this event, all matter and all energy were packed into one volume-less point
Biocorrelation
Biodiversity
The number of different species that exist at a given time
Biomass
The amount of organic material in a specified volume
Body fossil
A relict of an organism’s body, preserved in rock
Cambrian explosion
The remarkable diversification of life, indicated by the fossil record, that occued at the beginning of the Cambrian Period.
Cast
Sediment that preserves the shape of a shell it once filled before the shell dissolved or mechanically weathered away
Celestial object
An object (star, moon, planet, or galaxy) that lies outside of the Earth
Chemical bond
The invisible link that holds together atoms in a molecule and/or in a crystal
Chemical fossil (biomarkers)
Distinctive molecules or milecular fragments, formed from the remains of living organisms, that can be preserved in rock
Chemical reaction
Interactions among atoms and/or molecules involving breaking and forming chemical bonds
Comet
A ball of ice and dust, probably remaining from the formation of the Solar System, that orbits the sun
Compound
A material composed of two or more elements that cannot be separated mechanically; the smallest piece is a molecule
Continental crust
The crust beneath the continents
Convection
Heat transfer that results when warmer, less dense material rises while cooler, denser material sinks
Core
The dense, iron-rich centre of the Earth
Correlation
The process of defining the age relations between the strata at one locality and the strata at another
Critical zone
The portion of the Earth System, including the surface, the near-surface including soil, liquid water bodies, and the lower atmosphere, in which resources and conditions are important for sustaining life
Crust
the rock that makes up the outermost layer of the Earth
Daughter isotope
The isotope that is the product of the parent isotope’s decay
Deep-sea trench
The deep trough on the ocean floor that forms at a subduction zone where one plate slides beneath another
Differentiation (of a planet)
A process early in a planet’s history during which dense iron alloy melted and sank downward to form the core, leaving less dense mantle behind
Dipole
A magnetic field with a north and south pole, like that of a bar magnet
Disconformity
an unconformity parallel to the two sedimentary sequences it separates
Doppler effect
The phenomenon in which the frequency of wave energy appears to change when a moving source of wave energy passes an observer
Dwarf Planet
A celestial object that orbits the Sun, but has not cleared its orbit of debris
Earth System
The interacting of physical and biological assembly phenomena involving the solid Earth, the hydrosphere, the atmosphere reservoirs, and the biosphere.
Earthquake
A vibration causes by the sudden breaking or frictional sliding of rock in the Earth
Ecosystem
An environment and its inhabitants
Electromagnetic radiation
A type of energy emitted into space by a source; it travels in the form of waves that can pass through a vacuum
Electron shell
The distinct space around an atomic nucleus in which electrons move
Element
A material consisting entirely of one kind of atom; elements cannot be subdividied or changes by chemical reactions
Energy
The capacity to do work
Eon
The largest subdivision of geologic time
Epoch
An interval of geologic time representing the largest subdivision of a period
Equator
The great circle around the Earth that defines the boundary between the northern and southern hemisphere; it is halfway between the poles
Era
An interval of geologic time representing the largest subdivision of the Phanerozoic Eon
Expanding Universe theory
The theory that the whole Universe must be expanding because galaxies in every direction seem to be moving away from us
External processes
A geomorphologic process that is the consequence of gravity or of the interaction between the solid Earth and its fluid envelope (air and water); energy for these processes comes from gravity and sunlight
Extinction
The death of the last members of a species so that there are no parents to pass on their genetic traits to offspring
Extraordinary fossil
A rare fossilised relict, or trace, of the soft part of an organism
Fission reaction
A nuclear reaction during which the nucleus of a large atom splits
Fossil
the remnant, or trace, of an ancient living organism that has been preserved in rock or sediment
Fossil assemblage
a group of fossil specieis found in a specific sequence of sedimentary rock
Fossil correlation
a determination of the stratigraphic relation between two sedimentary rock units, reached by studying fossils
Fossilisation
The process of forming a fossil
Fusion reaction
A type of nuclear reaction during which nuceli collide and bond
Ga
billions of years ago
Galaxy
An immense system of hundres of billions of stars.
Genome
the succession of genes in strands of DNA
Geocentric model
An ancient Greek idea suggesting that the Earth sat motionless in the center of the universe while stars and other planets and the Sun orbited around it.
Geologic contact
The surface between two distinct geologic units
Geologic map
A map showing the distribution of rock units and structures across a region
Geologic time
The span of time since the formation of the Earth.
Geological time scale
A scale that describes the intervals of geoloic time
Geographic pole
The locations (north and south) where the Earth’s rotational axis intersects the planet’s surface.
Geology
The study of the Earth, including our planet’s composition, behaviour, and history.
Geothermal gradient
The rate of change in temperature with depth
Giant planets
The four outer, or Jovian, planets of our Solar System, which are significantly larger than the rest of the planets and consist largely of gas and/or ice.
Gravity
The attractive force that one mass exerts on another; the magnitude depends on the size of the objects and the distance between them
Ground water
Water that resides under the surface of the Earth, mostly in pores or cracks of rock or sediment
Habitable Zone
(for astronomy) the region in the Solar System where the intensity of radiation is sufficient to allow water to exist in liquid form on the surface of a planet
Half-life
The time it takes for half of a group of radioactive element’s isotopes to decay
Heliocentric model
An idea proposed by Greek philosophers suggesting that all heavenly objects including the Earth orbited the sun
Heliosphere
A bubble-like region in space in which solar wind has blown away most interstellar atoms
Hiatus
the gap in the geolic record that an unconformity represents
Index fossil
A fossil of an organism that lived during a relatively short period of time over a relatively large area of the Earth, and can be used for stratigraphic correlation
Internal process
A process in the Earth System ultimately cuased by the Earth’s internal heat.
Interplanetary space
The region of vacuum between the orbits of planets
Intersellar space
The region of vacuum between stars
Isotopes
Different versoins of a given element that have the same atomic number but different atomic weights
Ka
thousands of years ago
Kuiper Belt
A diffuse ring of icy objects, remants of Solar System formation, that orbit our Sun outside the orbit of Npetune
Lateral continuity
Light-year
The distance that light travels in 1 Earth year (about 9.5 trillion km)
Lithologic correlation
Looking for similarities in rock type in correlating formations in nearby regions
Lithosphere
The relatively rigid, nonflowable, outer 100- to 150-km-thick layer of the Earth, constituting the crust and the top part of the mantle.
Lithospheric mantle
The part of the plate, below the crust, in which mantle is cool enough to behave rigidly
Lower mantle
The deepest section of the mantle, stretching from 670 km down to the core-mantle boundary
Ma
millions of years ago
Macrofossil
A fossil large enough to be seen with the naked eye
Magnetic field
The region affected by the force emanating from a magnet
Magnetic field lines
The trajectories along which magnetic particles would align, or charges particles would flow, if placed in a magnetic field
Magnetism
An attractive or repulsive field force generated by permanent magnets or by an electrical current
Magnetosphere
The region protected from the electrically charged particles of the solar winds by the Earth’s magnetic field
Mantle
The thick layer of rock below the Earth’s crust and above the core
Marker bed
a particularly unique layer of sediment or sedimentary rock that provides a definitive basis for correlation
Mass
The amount of matter in an object (different to weight)
Mass-extinction event
A time when vast numbers of species abruptly vanish
Matter
The material substance of the Universe; consists of atoms and has mass
Meteroid
Any object from space that enters the Earth’s atmosphere
Microfossil
A fossil that can be seen only with a microscope
Mid-ocean ridge
A 2km-high submarine mountain belt that forms along a divergent oceanic plate boundary
Moho
The seismic-velocity discontinuity that defines the boundary between the Earth’s crust and mantle
Mold
In the context of fossils, a cavity in sedimentary rock left behind when a shell that once filled the space weathers out.
Molecule
The smallest piece of a compound that has the properties of the compound; it consists of two or more atoms attached by chemical bonds
Moon
A sizeable solid body locked in orbit around a planet
Natural Selection
The process by which the fittest organisms survive to pass on their characteristics to the next generation
Near-Earth object
A meteoroid whose path takes it close to the Earth, so thath there is a slight possibility that it could collide with the Earth.
Nebula
a cloud of gas or dust in space
Nebular theory fo planet formation
The concept that planets grow out of rings of gas, dust, and ice surrounding a newborn star
Nonconformity
A type of unconformity at which sedimentary strata overlie older metamorphic and or intrusive igneous rocks
Nuclear bond
The force that attaches subatomic particles to each other wihtin the nucleus of an atom
Nucleus
The central ball of an atom that consists of protons and neutrons
Numerical age
the age of a geological feature given in years (aka absolute age).
Oceanic crust
The crust beneath the oceans; composed of gabbro and basalt, overlain by sediment
Oort Cloud
A cloud of icy objects, left over from Solar System formation, that orbit the Sun in a region outisde of the heliosphere
Original horizontality
Organism
A self-contained living entity
Paleontologist
A scientist who specialises in studying and interpreting fossils
Paleontology
The study of ancient life and its evolution as recorded by fossils
Parent isotope
The isotope that undergoes radioactive decay
Period
An interval of geologic time representing a subdivision of a geologic era
Permineralisation
The fossilisation process in which plant material becomes transformed into rock by the precipitation of silica from groundwater
Petrified wood
Wood that has undergone permineralisation and has turned into agate; growth rings and cell walls may remain visible in samples
Phylogenetic tree
A chart representing the ideas of paleontologists showing which groups of organisms radiated from which ancestors
Planet
An object that orbits a star, is roughly spherical, and has cleared its neighbourhood of other objects
Planetesimal
Tiny, solid pieces of rock and metal that collect in a planetary nebula and eventually accumulate to form a planet
Plate
One of about 20 distinct pieces of the relatively rigid lithosphere
Precambrian
The interval of geoloic time between the Earth’s formation about 4.57 Ga and the beginning of the Phanerozoic Eon 539 Ma
preservation potential
The likelihood that an organism will be preserved as a fossil
Principle of uniformitarianism
internal and external geological processes we observe operating today also operated in the past, at roughly comparable rates throughout most of Earth’s history
Protoplanatery disk
The plate-shaped region of gas and dust, surrouding the newborn Sun, from which the planets formed
Protoplanet
A body that has grown by the acculuation of planetesimals but has not yet become a planet
Protostar
A dense body of gas that is collapsing inward because of graviational forces and that may eventually become a star
Radioactive decay
Isotopes that undergo a change which converts them into a different element
Radioactive isotopes
Unstable isotopes
Radiometric dating
the science of determining the age of materials in years by measuring the ratio of parent radioactive atoms to daughter product atoms in the material
Red Shift
The phenomenon in which a source of light moving away from you very rapidly shifts to a lower frequency, that is, toward the red end of the spectrum
Relative age
the age of one geological feature with respect to another
Scientific cosmology
The study of the overall structure and evolution of the Universe
Sediment
An accumulation of loose mineral grains such as boulders, pebbles, sand, silt, or mud that are not cemented together
Shatter cones
Small, cone-shaped fractures formed by the shock of a meteorite impact
Solar System
Our Sun and all the materials that orbit it (including planets, moons, asteroids, Kuiper Belt objects, and Oort Cloud Objects)
Star
An object in the Universe in which fusion reactions occur, producing vast amounts of energy
States of matter
Versions of a substance that differ from each other in the degree to which atoms or molecules in the ubstance are bonded to each other; solid, liquid, gas, plasma
Stellar nucleosynthesis
The production of new, larger atomd by fusion reactions in stars; the process generates more massive elements that were not produced by the Big Bang
Stellar wind
the stream of atoms emitted from a start into space
Strata
Stratigraphic column
A cross-section diagram of a sequence of strata summarising information about the sequence
stratigraphic formation
A recognisable layer of a specific sedimentary rock type or set of rock types, deposited during a certain time interval, that can be traced over a broad region.
Stratigraphic superposition
Stratigraphy
The study of layered rocks (i.e. strata) - and their relationship to other rocks)
Supernova
A short-lived, very bright object in space that results from the cataclysmic explosion markingt he death of a very large star
Surface water
Liquid or seasonally frozen water that resides at the surface of the Earth in oceans, lakes, streams, and marshes.
Taxonomy
The study and classification of the relationship among different forms of life
Terrestrial planets
Plants that are of comparable size and character to the Earth and consist of a metallic core surrounded by a rock mantle.
Theory of evolution by natural selection
The idea that species change over time, new species appear, and old species dissapear, due to the survival of the fittest
Theory of plate tectonics
The theory that the lithosphere consists of separate plates that move with respect to one another.
Topography
Variations in elevation
Trace fossil
Fossilised imprints or debris that an organism leaves behind while moving on or through sediment; examples include footprints, burrows, and coprolite
Transition zone
The middle portion of the mantle, from 400-670 km deep, in which there are several jumps in seismic velocity
Unconformity
a boundary between two different rock sequences representing an interval of time during which strate were not deposited and/or were eroded
Universe
All of space and all the matter and energy within it
Upper mantle
The uppermost section of the mantle, reaching down to a depth of 400 km
Vacuum
Space that contains very little matter in a given volume
Wavelength
the horizontal different between two adjacent wave troughs or two adjacent crests
