The Earth
The Earth is the most popular foundation module for Earth Sciences streams. In this module, you’ll learn about the history of the Earth, the origins of life, and an introduction to plate tectonics and climate. In the table below, you’ll find a list of the key terms you’ll be expected to understand.
| Term | Definition |
| Achondrites | An achondrite is a stony meteorite that does not contain chondrules. It consists of material like terrestrial basalts or plutonic rocks and has been differentiated and reprocessed to a lesser or greater degree due to melting and recrystallization on or within meteorite parent bodies. |
| After Glow Pattern | Also known as cosmic microwave background,the cosmic microwave background (CMB) is thought to be leftover radiation from the Big Bang, or the time when the universe began. |
| Aggregation | an aggregate is a mass of mineral crystals, mineraloid particles or rock particles. |
| Albedo | Albedo (al-bee-doh) is a measure of how much light that hits a surface is reflected without being absorbed. Something that appears white reflects most of the light that hits it and has a high albedo, while something that looks dark absorbs most of the light that hits it, indicating a low albedo. |
| Alpha decay | Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or ‘decays‘ into a different atomic nucleus, with a mass number that is reduced by four and an atomic number that is reduced by two. |
| Astronomical Units | Earth-Sun distance |
| Atmophile | Chemical elements or compounds which can be found in, attracted to, or having a tendency to occur in the atmosphere |
| Basaltic Rocks | Basalt is a dark-colored, fine-grained, igneous rock composed mainly of plagioclase and pyroxene minerals. It most commonly forms as an extrusive rock, such as a lava flow, but can also form in small intrusive bodies, such as an igneous dike or a thin sill. |
| Beta decay | radioactive decay in which an electron is emitted. |
| Bi-polar seesaw | is the phenomenon that temperature changes in the northern and southern hemispheres may be out of phase. |
| Big Bang Expansion | The Big Bang is a theory describing the expansion of our Universe from a point of origin roughly 13.8 billion years ago. This hypothetical starting point of everything was an infinite concentration of energy referred to as a singularity. |
| Black body | A perfect absorber and emitter of electromagnetic radiation |
| Brittle-Ductile Transition Zone | The brittle-ductile transition zone is the strongest part of the Earth’s crust. For quartz and feldspar rich rocks in continental crust this occurs at an approximate depth of 13–18 km. |
| Brownian Motion | the movement of particles in a liquid or gas, caused by being hit by molecules of that liquid |
| Calcium Aluminum Inclusion | A calcium–aluminum-rich inclusion or Ca–Al-rich inclusion (CAI) is a submillimeter- to centimeter-sized light-colored calcium– and aluminum-rich inclusion found in carbonaceous chondrite meteorites. |
| Centrifugal Force Formula | In Newtonian mechanics, the centrifugal force is an inertial force that appears to act on all objects when viewed in a rotating frame of reference. It is directed away from an axis which is parallel to the axis of rotation and passing through the coordinate system’s origin.
F=Mv^2/r Whereby: M= mass of the moving object v= velocity of the moving object in a circular motion r= the radius distance between the moving object to the axial of the circular motion. |
| Ceres | Dwarf planet Ceres is the largest object in the asteroid belt between Mars and Jupiter and the only dwarf planet located in the inner solar system. It was the first member of the asteroid belt to be discovered when Giuseppe Piazzi spotted it in 1801 |
| Chalcophile | In the Berzelius–Goldschmidt classification, chalcophile elements are elements with a low affinity for oxygen and which preferentially bond with sulfur to form sulfides. |
| Chondrites | A chondrite is a stony meteorite that has not been modified, by either melting or differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar System accreted to form primitive asteroids. |
| Chondrites Carbonaceous | Carbonaceous chondrites, a class of meteorites that is almost identical in composition to the photosphere of the Sun. |
| Chondrites Enstatite | Enstatite Chondrites are a small class of meteorites which contain an unusually large assortment of minerals which have not been found on earth or even, in some cases, in other meteorites. |
| Chondrites Ordinary | Ordinary chondrites are by far the most common type of meteorite to fall to Earth: about 80% of all meteorites and over 90% of chondrites are ordinary chondrites. |
| Climate Drivers | Natural climate drivers include changes in the sun’s energy output, regular changes in Earth’s orbital cycle, and large volcanic eruptions that put light-reflecting particles into the upper atmosphere. |
| Climate Sensitivity | Climate sensitivity is the amount by which planet warms after a doubling of greenhouse forcing |
| Condensation sequence | In planetary science, the condensation sequence refers to the order in which chemical compounds transition from gas to solid phase in a protoplanetary nebula (disk), based on the condensation temperature of each compound. |
| Continental Crust | the surface of the earth that is about 35 kilometresthick and includes the landmasses and the solidrock below them |
| Continental Drift | Continental drift is the theory that the Earth’s continents have moved over geologic time relative to each other, thus appearing to have “drifted” across the ocean bed. |
| Convergent plate boundaries | Lithospheric plates move towards each other, and are associated with subduction zones and volcanism at volcanic arcs |
| Creep | Creep, in geology, slow downslope movement of particles that occurs on every slope covered with loose, weathered material. |
| Dansgaard-Oeschger event | Dansgaard–Oeschger event, also called D-O event, any of several dramatic but fleeting global climatic swings characterized by a period of abrupt warming followed by a period of slow cooling that occurred during the last ice age. |
| Dark Ages | It is the period of the first 500 million years (Hadean era) where the scientist knows nothing about because of lacking in geological evidence. |
| Dark Energy | Dark energy is an enigmatic phenomenon that acts in opposition to gravity and is responsible for accelerating the expansion of the universe.
It has a mysterious quantity that makes up, along with dark matter, most of the mass of the universe. |
| De-extinction | The exploitation of genetic technology and DNA from historical specimens or fossils to revive species that have gone extinct. |
| Debris avalanches | A debris avalanche is formed when an unstable slope collapses and debris is transported away from the slope. |
| Divergent plate boundaries | Lithospheric plates move away from each other and are associated with volcanism at rift zones and mid-ocean ridges. |
| Eccentricity | Non-circularity of a planets orbit |
| Fayalite | Has a chemical compund formula of Fe2SiO4, is a black or brown mineral which is an iron-rich form of olivine and occurs in many igneous rocks. |
| Foraminifera | Foraminiferan, any unicellular organism of the rhizopodan order Foraminiferida (formerly Foraminifera), characterized by long, fine pseudopodia that extend from a uninucleated or multinucleated cytoplasmic body encased within a test, or shell. Depending on the species, the test ranges in size from minute to more than 5 cm (2 inches) in diameter and varies in shape, number of chambers, chemical composition, and surface orientation. |
| Forsterite | Forsterite (Mg2SiO4; commonly abbreviated as Fo; also known as white olivine) is the magnesium-rich end-member of the olivine solid solution series. It is isomorphous with the iron-rich end-member, fayalite. |
| Gamma decay | Gamma decay, type of radioactivity in which some unstable atomic nuclei dissipate excess energy by a spontaneous electromagnetic process. |
| Geoid | The geoid is a model of global mean sea level that is used to measure precise surface elevations. |
| Geotherm | A graph of temperature as a function of depth in the earth’s crust; a geothermal gradient. |
| Glaciation | Glaciation is the formation, movement and recession of glaciers. |
| Gravitational Force Formula | Is the product between two large bodies over the squared distance between the two bodies.
F=-GM1M2/r^2 G= Gravitational constant M1= Body Mass 1 M2= Body Mass 2 r= The distance between the center of Body Mass 1 and 2. |
| Great Oxidation event | The Great Oxygenation Event occurred when cyanobacteria living in the oceans started producing oxygen through photosynthesis. As oxygen built up in the atmosphere anaerobic bacteria were killed leading to the Earth’s first mass extinction. |
| Ground deformation | Normally characterised by dome-like inflation of the caldera. Uplift is often highest near the caldera centre. Rates of uplift are often mm or cm per year but can be as high as metres per year. Increases in Volcanic-tectonic earthquakes often accompany episodes of uplift. |
| Habitable Zone | The habitable zone is the area around a star where it is not too hot and not too cold, at the right pressure for liquid water to exist on the surface of surrounding planets. |
| Heinrich event | An event whereby massive releases of icebergs from Nothern ice sheets, which happened during the cooling part of each Dansgaard-Oeschger cycle. |
| Hotspot chains | Produces linear chains of volcanoes where the eruptions are located away from the plate boundaries. |
| Howardite-Eucrite-Diogenites | The howardite, eucrite and diogenite (HED) clan of meteorites are ultramafic and mafic igneous rocks and impact-engendered fragmental debris derived from a thoroughly differentiated asteroid |
| Inflation | is a theory of exponential expansion of space in the early universe. The inflationary epoch lasted from 10⁻³⁶ seconds after the conjectured Big Bang singularity to some time between 10⁻³³ and 10⁻³² seconds after the singularity. |
| Intraplate Volcanism | Volcanism which occurs away from the plate boundaries |
| Isostasy | Isostasy is a fundamental concept of equilibrium in the Geology. It is the idea that the lighter crust must be floating on the denser underlying mantle. Isostatic equilibrium is an ideal state where the crust and mantle would settle into in absence of disturbing forces. |
| Isotope | Isotopes are atoms of the same element that have different numbers of neutrons but the same number of protons and electrons. |
| Kola Superdeep Borehole | The Kola Superdeep Borehole is the result of a scientific drilling project of the Soviet Union in the Pechengsky District, on the Kola Peninsula. The project attempted to drill as deep as possible into the Earth’s crust. With a depth of 12,262 metres, it has been since 1989 the deepest artificial point on Earth. |
| Lahars | Volcanic mudflows containing a mixture of water, mud, ash, and other volcanic material that flows down the flank of volcanoes and into the river valleys, moving at the velocity of about 55m/s. |
| Large Calderas | Calderas are circular or moderately elliptical volcanic depressions, with diameters ranging between five and several tens of km. Ex Yellowstone |
| Lava flows | Streams of lava (molten rock) moving at the rates of 10m/hr to 10km/hr typically created during effusive(non-explosive) eruptions. |
| Lithophile | Lithophile is a term used to refer to elements that are prefer- entially partitioned into silicate minerals as opposed to sul– fides or metals. |
| Long Period earthquakes | Also known as tremor, a movement of magma and/or hydrothermal fluids. |
| Long-wave radiation | Electromagnetic radiation emitted by the surface and atmosphere at wavelengths between 3 and 100 μm, i.e. within the range of infrared radiation. |
| Love Wave | A Love wave is a surface wave having a horizontal motion that is transverse (or perpendicular) to the direction the wave is traveling. |
| Luminosity | the brightness of a star in comparison with that of the sun: the luminosity of Sirius expressed as 23 indicates an intrinsic brightness 23 times as great as that of the sun. |
| Magnetic Stripes | a strip of magnetic material on which information may be stored, as by an electromagnetic process, for automatic reading, decoding, or recognition by a device that detects magnetic variations on the strip. |
| Marine Isotope Stages | Marine isotope stages (MIS), marine oxygen–isotope stages, or oxygen isotope stages (OIS), are alternating warm and cool periods in the Earth’s paleoclimate, deduced from oxygen isotope data reflecting changes in temperature derived from data from deep sea core samples. |
| Matrix | Matrix, in geology, the material in which something is embedded, either the natural rock that holds crystals, fossils, pebbles, mineral veins, and the like, or the fine-grained materials that surround larger grains in a rock |
| Melanosomes | Colour-bearing organelles. |
| Mesosiderites | Mesosiderites are a class of stony–iron meteorites consisting of about equal parts of metallic nickel-iron and silicate. They are breccias with an irregular texture; silicates and metal occur often in lumps or pebbles as well as in fine-grained intergrowths. |
| Milankovitch theory | The Milankovitch theory tries to explain the differences in climates and temperatures around the world over time based on the changes in earth’s orbit, axial rotation and axial tilt. |
| Nebular Theory | This states that the solar system developed out of an interstellar cloud of dust and gas, called a nebula. |
| Nuclear Fusion | the process of joining two nuclei to produceenergy |
| Ocean Acidification | When carbon dioxide (CO2) is absorbed by seawater, chemical reactions occur that reduce seawater pH, carbonate ion concentration, and saturation states of biologically important calcium carbonate minerals.
CO2 + H2O ↔ H2CO3 ↔ HCO3- + H+ ↔ CO32- + 2H+ |
| Ocean Bathymetry | Bathymetry is the study of underwater depth of ocean floors or lake floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. |
| Oceanic ridge | Oceanic ridge, continuous submarine mountain chain extending approximately 80,000 km (50,000 miles) through all the world’s oceans. |
| Olivine | Olivine is a green rock-forming mineral found mainly in dark-colored igneous rocks and thought to be the most abundant mineral in the mantle. |
| Organelles | A specialised structures found in the cell. |
| P wave | Primary (or Pressure) Waves. A P wave, or compressional wave, is a seismic body wave that shakes the ground back and forth in the same direction and the opposite direction as the direction the wave is moving. |
| Pallasites | The pallasites are a class of stony–iron meteorite. |
| Planetary Accretion | In astrophysics, accretion is the accumulation of particles into a massive object by gravitationally attracting more matter, typically gaseous matter, in an accretion disk. Most astronomical objects, such as galaxies, stars, and planets, are formed by accretion processes. |
| Planetesimal | one of the small celestial bodies that, according to one theory (planetesimal hypothesis), were fused together to form the planets of the solar system. |
| Planetesimal Hypothesis | The theory states that the planets were formed by the accumulation of extremely small bits of matter (planetismals) revolved around the sun. This matter was produced when a passing star almost collided with the sun. During the near-collision, hot gases were pulled out of both stars and the gases then condensed. |
| PP-Precursors | The PP precursors are seismic waves that form from underside reflections of P waves off discontinuities in the upper mantle transition zone (MTZ). |
| Pyroclastic density currents (PDCs) | A fast-moving current of hot gas and volcanic debris at the velocities of 30-100m/s that flows down the flanks of a volcano. |
| Pyroxene | Pyroxene, any of a group of important rock-forming silicate minerals of variable composition, among which calcium-, magnesium-, and iron-rich varieties predominate. |
| Quantum Fluctuation | In quantum physics, a quantum fluctuation is the temporary change in the amount of energy in a point in space, as prescribed by Werner Heisenberg’s uncertainty principle. |
| Rayleigh Wave | Rayleigh waves are generated by the interaction of P- and S- waves at the surface of the earth, and travel with a velocity that is lower than the P-, S-, and Love wave velocities. |
| S wave | Secondary (or Shear) Waves. An S wave, or shear wave, is a seismic body wave that shakes the ground back and forth perpendicular to the direction the wave is moving. |
| Seismicity | An increase in the number of low magnitude earthquakes. There are two types Long Period earthquakes/tremor and Volcanic-tectonic earthquakes. |
| Seismology | Seismology is the study of earthquakes and seismic waves that move through and around the earth. |
| Shield Volcanoes | Shield Volcanoes are large, gently sloping volcanoes formed almost exclusively by successive lava flows. Eruptions occur from a central vent but also from the flanks of the volcano. Ex Mauna Loa |
| Short-wave radiation | Shortwave radiation (SW) is radiant energy with wavelengths in the visible (VIS), near-ultraviolet (UV), and near-infrared (NIR) spectra. There is no standard cut-off for the near-infrared range; therefore, the shortwave radiation range is also variously defined. |
| Siderophile | Siderophile means “iron-loving”. This can refer to: Siderophilic bacteria, bacteria that require or are facilitated by free iron. Siderophile elements, chemical elements such as iridium or gold that tend to bond with metallic iron, as described by the Goldschmidt classification. |
| Snell’s Equation | Snell’s law, in optics, a relationship between the path taken by a ray of light in crossing the boundary or surface of separation between two contacting substances and the refractive index of each.
n1/n2 = sin α2/sin α1. |
| Snowball Earth | Periods of Earth history when ice extended all the way to the equator, and the ocean were frozen or mostly frozen. |
| Solar flux | Solar flux, or concentrated sunlight, is a measure of how much light energy is being radiated in a given area. |
| Solar Photosphere | The photosphere is the visible surface of the Sun that we are most familiar with. |
| SS-Precursors | SS precursors are underside reflections from velocity discontinuities that arrive before the main SS phase due to shorter paths through the upper mantle. |
| Stefan-Boltzman constant | Stefan-Boltzmann law, statement that the total radiant heatpower emitted from a surface is proportional to the fourth power of its absolute temperature.
5.7 x 10^-8 Wm^-2K^-4 |
| Stratovolcanoes | Stratovolcanoes are steep-sided and often symmetrical cone-shaped volcanoes made up of alternating layers of pyroclastic material and solidified lave. Ex Mt Fuji |
| Subduction Zone | A subduction zone is a region of the Earth’s crust where tectonic plates meet. Tectonic plates are massive pieces of the Earth’s crust that interact with each other. The places where these plates meet are called plate boundaries. |
| Telluric Planets | A terrestrial planet, telluric planet, or rocky planet is a planet that is composed primarily of silicate rocks or metals. |
| Tephra fall | Ash that is formed from the fragmentation of magma during explosive eruptions which is being ejected into the atmosphere via an eruption column. |
| The Ocean Conveyor | The global ocean conveyor belt is a constantly moving system of deep-ocean circulation driven by temperature and salinity. |
| Thermohaline circulation | Thermohaline circulation, also called Global Ocean Conveyor or Great Ocean Conveyor Belt, the component of general oceanic circulation controlled by horizontal differences in temperature and salinity. It continually replaces seawater at depth with water from the surface and slowly replaces surface water elsewhere with water rising from deeper depths. |
| Topography | the physicalappearance of the naturalfeatures of an area of land, especially the shape of itssurface |
| Transform plate boundaries | Lithospheric plates move laterally past each other but are not normally associated with volcanism. |
| Vesta | Vesta is unique among asteroids in that it has light and dark patches on the surface, much like the moon. Ground-based observations determined that the asteroid has basaltic regions, meaning that lava once flowed across its surface. |
| Volcanic arcs | Produces linear chains of volcanoes where they are located at the margins of tectonic plates. |
| Volcanic Hot spot | A volcanic hotspot is an area in the mantle from which heat rises as a thermal plume from deep in the Earth. Mantle plumes rise to the base of the lithosphere, where the high heat and low pressures facilitates melting and magma production, triggering hotspot volcanic activity. |
| Volcanic lightning | Volcanic lightning is an electrical discharge caused by a volcanic eruption, rather than from an ordinary thunderstorm. Volcanic lightning arises from colliding, fragmenting particles of volcanic ash, which generate static electricity within the volcanic plume, leading to the name dirty thunderstorm. |
| Volcano-tectonic earthquakes | Brittle fracture of rock as magma intrudes and pressures. |
| Xenoliths | A xenolith is a piece of rock trapped in another type of rock.
Most of the time, a xenolith is a rock embedded in magma while the magma was cooling. Magma is the molten rock beneath the Earth’s crust that emerges as lava during a volcanic eruption. The rock that forms from cooled magma is called igneous rock. Xenoliths are different types of rock embedded in igneous rock. |