Tectonics KEY WORDS

KEY WORDS FOR TECTONICS

Core the centre of the earth

Crust the thin layer at the earth’s surface

Plates sections of the earth’s crust

Convection currents changes in the flow and pressure of the earths mantle affecting Plate movement

Compressional plate boundary (margin) where two plates move together – DESTRUCTIVE BOUNDARY

Subductive zone where a plate is sinking and melting

Geosynclines a depression between two plates

Sedimentary rocks rock forms from sediment laid down under water

Anticlines an upfold, like an arc

Syncline a downfold

Nappes a severe form of folding where the rocks have moved along a fracture

Lava the name given to molten magma when it erupts at the surface

Acid lave thick, viscous lava with a high silica content, flows short distances

Basic lava thin ‘runny’ lava, low silica content, flows long distances

Vent the opening through which the lava flows in a volcano

Tensional plate boundary (margin) where two plates are moving apart (CONSTRUCTIVE)

Seismography measures and records the intensity of an earthquake

Richter scale measures the strength of an earthquake

Focus the point on the earth’s surface directly above the epicenter

Epicenter the point within the earth’s crust where the primary earthquake occurred

Primary effects (of an earthquake) the direct effects of an earthquake e.g. buildings collapsing

Secondary effects (of an earthquake) the indirect effects e.g. fire, tidal waves, disease

Fire example of a secondary effect of an earthquake (see above)

Tsunamis huge tidal waves caused by submarine earthquakes

Landslides rapid movement of rocks and soil under the influence of gravity

Disease illness often caused by a natural disaster

CONSTRUCTIVE MARGIN – where the plates slip past each

COLLISION Boundary – where plates of the same density collide and form FOLD MOUNTAINS