GEOCHEMICAL MODEL: CRUST: aluminium silicates, Continental (heterogeneous, granite is abundant) Oceanic (homogeneous, basalt mainly) MANTLE: igneous rocks rich in iron and magnesium silicates. Mainly peridotite. The MANTLE has been traditionally divided into: upper mantle transition zone (denser materials due to higher temperature and pressure) lower mantle. but this layers do not have significant differences in chemical composition, the differences are of state and behaviour  CORE: almost pure iron mixed with iron sulphides and nickel. Geochemical model The CORE has been traditionally divided into: outer core, inner core, but this layers do not have significant differences in chemical composition, the differences are of state and behaviour.GEODYNAMIC MODEL: Different layers according to: physical states (plasticity-rigidity/density), mechanical properties (how respond to variation in temperature or pressure). LITHOSPHERE: includes the crust and the upper part of the upper mantle rigid (solid) divided (fractured) into large blocks, lithospheric plates: Horizontal movements that are dragged along by the mantle underneath, Vertical movements due to isostatic adjustment. ASTENOSPHERE (or SUBLITHOSPHERIC UPPER MANTLE): includes the rest of the upper mantle and the transition zone (lies between lithosphere and mesosphere), maleable plastic, tendency to flow as the lithosphere moves. MESOSPHERE: is the lower mantle from aprox. 670 km deep to D’ layer, semi-solid flows slowly cm/year ,not static: cold lithospheric plates from subduction zones descend into it mantle plumes can enter it from D” layer underneath. D’’ LAYER: one of the MOST DYNAMIC layers of the Earth. liquid due to the heat that accumulates here from the outer core, hot magma:escapes from this layer creating MANTLE PLUMES: break through the mantle and the lithosphere creating at the Earth’s surface HOTSPOTS: intense volcanic activity (for example the Hawaiian Islands) OUTER CORE: liquid due to the heat of the inner core that flows in VIOLENT CURRENTS: convection currents that generate the MAGNETIC FIELD of the Earth; invisible dynamic lines of force that cross the Earth, between the two magnetic poles. INNER CORE: solid due to the pressure of the overlaying materials, the center is 6378 km deep, the temperature is higher than 6000 ºC, produces geothermal energy.INTERNAL DYNAMICS: In the mantle, hot magma plumes from the D´layer generate an ascending current. Graviti acting on the lithospheric plates generates a descending current. If the layers have different densities, like the magnetic core and the rocky mantle, they cannot mix. As a result, independig convection currents are generated. GEOTHERMAL GRADIENT: The internal temperatura of the earth increases as the surface increases. HEAT FLOW: The amount of heat energy that reach the surface, heat travels from the hot interior of the Earth to the surface, transmition is very slowly. CONVECTION CURRENT: Hot materials, which are less dense and ascend to the surface. As they cool, these materials become denser and sink again. This continuous flow is generated by  high temperatura variations between the lithospher and the D´layer PLATE TECTONICS: is a scientific theory that describes the large-scale motions of Earth’s lithosphere. The model builds on the concepts of continental drift, developed during the first few decades of the 20th century (Wegener). The geoscientific community accepted the theory after the concepts of seafloor spreading were developed in the late 1950s and early 1960s.EVIDENCES of plate tectonics:maps of the seafloor show mid-ocean ridges, oceanic trenches and large underwater faults, direct measurements:, have demonstrated that the plates are moving, indicate the direction of the movement, sediment deposits: are thicker at continental margins almost non-existent at mid-ocean ridges, the newest crust is found at the centre of mid-ocean ridges(the age increases with distance from ridge towards continents).PRINCIPLES The lithosphere is broken up into tectonic plates (there are seven or eight major plates and many minor plates). Where plates meet, plate tectonic boundaries, there is intensive seismic (earthquakes) and volcanic activity. At these boundaries: relief is created (mountain-building, emerged or submerged, and oceanic trench formation). MANTLE CONVECTION CURRENTS: slow motion of Earth’s semi-solid mantle caused by convection currents carrying heat from the interior of the Earth to the surface.PLATE TECTONICS: MANTLE CONVECTION:the lithosphere (made up by the crust and the solid upper part of the upper mantle) moves over the rest of the upper mantle, Lithosphere is divided into a number of lithospheric plates that are continuously being created and destroyed at opposite plate boundaries: ridges and trenches, Accretion occurs as mantle is added to the growing edges of a plate (seafloor spreading). This hot added material cools down by conduction and convection of heat. MID-OCEAN RIDGES:At the destruction edges of the plate, the material has thermally contracted to become denser, and it sinks under its own weight in the process of subduction usually at an ocean trench. SUBDUCTION ZONES or OCEAN TRENCHES: The relative motion of tectonic plates determines the type of boundary: convergent, divergent, or transform. DIVERGENT BOUNDARIES: where two plates are moving apart. The space created can also fill with new material sourced from molten magma that forms below: lithosphere is created. Divergent boundaries can form within continents but will eventually open up and become ocean basins. On land: Divergent boundaries within continents initially produce rifts, which produce rift valleys. Under the sea:The most active divergent plate boundaries are between oceanic plates and are often called mid-oceanic ridges. TRANSFORM BOUNDARIES: where plates slide past each other. The relative motion of the plates is horizontal. They can occur underwater or on land, and crust is neither destroyed nor created. Because of friction, stress builds up in both plates and when it exceeds the threshold* of the rocks, the energy is released causing earthquakes.CONVERGENT BOUNDARIES: where two plates are colliding. Subduction zones occur when one or both of the tectonic plates are composed of oceanic crust. The denser plate is subducted underneath the less dense plate. The plate being forced under is melted and destroyed. Where oceanic crust meets ocean crust Island arcs and oceanic trenches occur when both of the plates are made of oceanic crust. These are often associated with submarine volcanoes. Where oceanic crust meets continental crust The denser oceanic plate is subducted, often forming a mountain range on the continent. The Andes is an example of this type of collision. Obduction zones occur where continental crust meets continental crust Both continental crusts are too light to subduct so a continent-continent collision occurs, creating especially large mountain ranges. The most spectacular example of this is the Himalayas.