EARTH SYSTEMS KEY WORD GLOSSARY Click here to return to the Earth Systems Revision Page Earthquake - The violent movement of the ground caused by sudden movement along a fault releasing seismic waves. Fault - A fracture in the earth's crust along which rocks move relative to each other. Plate Tectonics - The theory and study of plate formation, movement, interactions and destruction Lithosphere - consists of the crust and the upper layer of the mantle Asthenosphere - consists of the semi-molten mantle within which convection currents occur Convection Currents - The transfer of heat from the earth's interior to the surface through the asthenosphere Crust - the outermost layer of the lithosphere Mantle - the main bulk of the solid earth, between the crust and the core Core - The central part of the earth below a depth of 2,900km, believed to consist of Iron and Nickel Sea Floor Spreading - the process by which new ocean floor is created at ridges as two plates diverge Constructive Plate Boundary (divergent boundary) - Where two plates move away from each other and new oceanic crust is formed Destructive Plate Boundary (convergent boundary) - Where two plates move towards each other and oceanic crust is destroyed by subduction Conservative Plate Boundary - Where two plates move sideways past each other and land is neither created nor destroyed. Collision Plate Boundary - Where two continental plates collide, resulting in the formation of fold mountains. Oceanic Ridge - An underwater mountain range developed at a divergent plate boundary where magma rises up through a cracking and widening ridge Rift Valley - A trough formed at a divergent plate boundary Ocean Trench - A long depression in the ocean floor at the junction of two plates where one is subducted under the other Fold Mountains - Mountains formed by the buckling of the earth's crust (at destructive or collision boundaries) Island Arc - A linear / arc-shaped chain of volcanic islands formed at a convergent plate boundary Subduction - The sinking of an oceanic plate beneath an overriding plate (at convergent plate boundaries) Convergence - Two plates moving away from each other Divergence - Two plates moving away from each other Extrusive Igneous Activity - Where volcanic materials (lava / ash) reach the surface in the form of volcanic eruptions Intrusive Igneous Activity - Where magma is injected into the earth's crust (it does not reach the earth's surface) Batholith - A large igneous dome shaped discordant intrusion Dyke - A vertical / discordant intrusion formed where magma has been injected vertically into the crust, forcing open existing fractures or creating new ones. Sill - A horizontal / concordant intrusion formed where magma is intruded along bedding planes between existing rocks. Now test yourself on your key terms using the online flash cards. Click here for other on-line quizzes related to the Earth Systems Unit Click here to return to the Earth Systems Revision Homepage |
