Ash: Powdery material thrown out by a volcano.
Lava: Rock that in its molten form (as magma) issues from volcanoes; lava is what magma is called when it reaches the surface.
Crater: A bowl-shaped depression at the mouth of a volcano or geyser.
Convection Current: The specific pattern of the movement of a fluid due to differences in temperature and density in the fluid.
Plate: The surface of the earth is composed of many large plates which slowly move around the planet, meeting and diverging, creating a variety of earthquakes, volcanoes, and mountains at their margins.
Crust: The outer layer of the Earth.
Mantle: The layer of the earth between the crust and the core.
Core: The core is a layer rich in iron and nickel found in the interior of the Earth. It is composed of two sub-layers: the inner core and outer core. The core is about 7,000 kilometres in diameter.
Constructive Boundary: Occur where two plates slide apart from each other. Mid-ocean ridges (e.g. Mid-Atlantic Ridge) and active zones of rifting (such as Africa's Great Rift Valley) are both examples of divergent boundaries.
Destructive Boundary: Occur where two plates slide towards each other commonly forming either a subduction zone (if one plate moves underneath the other) or a continental collision (if the two plates contain continental crust).
Subduction Zone: Is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge.
Ocean Trench: The oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. They are also the deepest parts of the ocean floor.
Fold Mountain: Fold Mountains are a type of mountain range that is formed when two continental plates collide (or one continental plate colliding with an oceanic plate). The colliding crust is compressed and pushed upwards (uplifted), forming mountains.
Anticline: A ridge-shaped fold of stratified rock in which the strata slope downward from the crust.
Syncline: A through or fold of stratified rock in which the strata slope upward from the axis.
Earthquake: A sudden and violent shaking of the ground, sometimes causing great destruction, as a result of movements within the earth's crust or volcanic action.
Epicentre: The point on the earth's surface directly above the hypocentre, where the energy of an earthquake is first released.
Focus: it is right above the epicentre.
Tsunami: A long high sea wave caused by an earthquake or other disturbance.
Richter scale: A numerical scale for expressing the magnitude of an earthquake on the basis of seismograph oscillations.
Seismic wave: An elastic wave in the earth produced by an earthquake.
Supervolcano: Is an enormous volcano that is an order of magnitude larger than ordinary volcanoes. A supervolcano occurs when a huge magma chamber in the Earth's crust erupts after being under great pressure, causing a large caldera to form as the land over the magma chamber collapses.
Mercalli scale: A twelve-point scale for expressing the local intensity of an earthquake.
