Alexandre SCHOHN

Dictionary of geology


Deposits: sediments of lakes and water courses composed of shuffleboard, gravel and sand depending on the region and the intensity of the current.

Shield: large proportion of the former base mainly consists of magmatic and metamorphic age usually Precambrian rocks (4453 – 542 my).

Continental craton: field with a continental crust composed mainly of granite and any measure of metamorphic rock such as gneiss.

Time scale: millions of years are written in my.

Explosive eruption: a volcanic eruption characterised by the emission of lava fragmented in the atmosphere, in contrast to the effusive eruptions which emit mainly fluid lavas in the form of lava flows

Geothermal energy: the Greek geo (Earth) and thermos (heat) is a word that means both the science that studies the internal thermal phenomena of the terrestrial globe, and technology that aims to exploit it.

Geothermal gradient: is the increase of temperature in the basement as you move away from the surface. The average gradient in Europe is about 1 ° C 33-meter or 3 ° C every 100 metres.

Green stone: magmatic rock whose green hue is due to the appearance of green minerals via alteration and metamorphism.

Lithosphere: Surface layer of the Earth, relatively rigid, thick of a hundreds of kilometres, comprising the crust and part of the upper mantle. It is divided into mobile plates on their base (substratum) more viscous called asthenosphere.

Asthenosphere: part ductile of Earth's upper mantle. It extends from the lithosphere to the lower mantle on 700 kilometres.

Composition of the Earth
Composition of the Earth

Orogen: The orogenesis is the scientific term for the set of mechanisms of formation of the mountains.

  • Collision Orogen: when two continental plates of the same nature and density meet the movement is blocked. It is not possible to dive one of the plates under another (subduction). The two plates welded to form a single to create mountains.

  • Orogen of subduction: the subduction is the mechanism by which an oceanic tectonic plate bends and dives under another plate before sinking into the mantle. This causes a volcanic activity and the formation of volcanoes and mountains on the plate no affect.

Orogenic cycle: first orogen by subduction. Second by collision orogen
Orogenic cycle: first orogen by subduction. Second by collision orogen



Pangea is a supercontinent formed from the collision of the Laurussia and the Protogondwana Carboniferous and gathering all of the world's land. In the Triassic, it fragmented in Laurasia in the North and Gondwana in the South.

Rift: The rift is opening by extension of part of the Earth's crust. During this open, the crust thins and form a ditch collapse.  During the extension, normal faults appear forming levels giving the rift a stair shape. It can represent the initial training from coast-to-coast Stadium if it is initially located on a continent.

Evolution of a rift with its opening

Metamorphic rock: formed without a merger activity (volcanism, magma,…) from pre-existing rocks, and this essentially by recrystallization (restructuring at the molecular level) due to the temperature and the pressure rises.

Sedimentary rock: results from the accumulation of elements (minerals, winnow debris fragments, etc…).

Magmatic rock: results from the solidification of magma. It has two types of rocks

Igneous rock: having solidified (crystallized) within the lithosphere

Volcanic rock: wash, etc. being solidified, at least in part, to the surface of the lithosphere (volcanoes, oceanic volcanoes, etc…)

Rodinia: Formed the supercontinent, which contains most or all of the continental masses of that time, there are about 1 100 million years from heart and was surrounded by a called Mirovia ocean. Continental movements before its formation are not well known. 750 million years ago, it split into eight continents and their drift cause its dislocation and a re-Assembly in a new supercontinent: Pangea

Supercontinent: gathering of many plates forming a continent of a large size. For example, Eurasia (currently), the Pangaea (300 my) and the Rodinia (1000 my).