volcanoes

Acid Lava thick, viscous lava with high silica content, only flows short distances.

Basic lava thin �runny� lava, low silica content, flows long distances.

Composite volcano a steep-sided cone with layers of ash and lava.

compressional margin where two tectonic plates are moving together. (destructive margin or boundary)

Conservative margin where two tectonic plates sliding past each other either in the same or opposite directions.

Continental plate a huge section of the earth�s crust.

Earthquake a sudden concentrated shaking of the earth�s crust.

Epicentre the point on the surface from which the energy waves of an earthquake spread out.

Focus the point below the surface from which the energy waves of an earthquake spread out.

Fold mountains mountains formed by plate movements folding or crumpling up continental crust.

Richter scale a scale that measures the strength of an earthquake.

Shield volcano a volcano with gentle sides and a wide base. Made from basic lava.

Subduction zone an area where oceanic crust is pushed down underneath continental crust at a compressional margin.

Tectonic activity changes taking place in the structure of the earth. The movement of tectonic plates due to convection currents within the earth. (continental drift)

Tensional margin where two tectonic plates are moving apart.
(constructive margin or boundary)

Volcano a cone shaped mountain created by the lava from repeated eruptions.