3.1 Elementary plate tectonics Flashcards
Benioff zone
Narrow zone of deep earthquake foci at a subduction zone.
Continental crust
Part of the Earth’s crust that forms the continents.
Continental drift
Theory that the continents have drifted across the surface of the globe.
Convergent plate boundaries
Margins where plates are moving towards each other.
Core
Central part of the Earth below 2900 km from the surface.
Crust
Outermost layer of the Earth. It may be divided into continental and oceanic.
Divergent plate boundaries
Plate boundaries in which the plates are moving apart.
Hotspot
Relatively small area where magma rises through a continental or ocean plate. As the plate moves across a hot spot a chain of volcanoes may be formed
Island arcs
Chains of volcanic islands on the continental side of an ocean trench. Associated with a subduction zone.
Lava
Molten magma that reached the Earth’s surface
Lithosphere
Outermost layer of the Earth, comprising the crust and part of the mantle.
Magma
Molten rock within the Earth. When it reaches the surface it is called lava.
Mercalli Scale
Scale of earthquake intensity based of descriptive data.
Mid-ocean ridges
Lines of mainly mountains formed when two ocean plates are separating
Oceanic crust
Part of the crust underlying the oceans.
Oceanic trenches
Arc-shaped depressions formed at subduction zones where one tectonic plate plunges a less dense continental one.
Oceanic ridges
Largest feature of the ocean floor. They are essentially a linear belt of submarine mountains.
Ritcher scale
Open ended scale to record the magnitude of earthquakes.
Sea-floor spreading
Where ocean floors grow as plates move apart at constructive margins.
Shield
Continental area that has not been deformed since Pre-Cambrian times.
Subduction zone
Area where one plate sides beneath another, where earthquakes occur.
