Chapter 6 Flashcards
What is a natural hazard?
Naturally occurring physical phenomena caused by rapid or slow onset events, can be geophysical/tectonic or climatical/hydrological.
Define natural disaster.
Serious disruption to the community as a result of a natural hazard.
What is a supervolcano?
A volcano that erupts at least 1000km3 of material.
What does the plate tectonic theory describe?
The large-scale motion of seven large plates and the movements of smaller plates of the Earth’s lithosphere.
What is a destructive (convergent) boundary?
It is where two plates, specifically the oceanic and continental plates, collide.
What occurs in a subduction zone?
One or both of the tectonic plates are composed of oceanic crust.
What is an ocean trench?
A depression of the ocean floor that runs parallel to a destructive plate boundary.
Define the Benioff zone.
A dipping, roughly planar zone of increased earthquake activity produced by the interaction of a downgoing oceanic crustal plate with an overriding continental or oceanic plate.
What is a constructive (divergent) boundary?
It is where plates move apart causing the appearance of a crack.
What is seafloor spreading?
A geological process in which tectonic plates split apart from each other.
Define a volcano.
A rupture in the crust of the planetary mass object that allows hot lava, volcanic ash, gases, and pyroclastic material to escape from a magma chamber below the surface.
What characterizes a composite (strato) volcano?
Built up by alternating layers of lava and ash, conical in shape.
What is an acidic volcano?
A volcano made up of just lava, which is thick and doesn’t flow easily, giving the volcano steep sides.
Define an island arc.
A chain of volcanic islands formed when two oceanic plates move towards each other causing the denser and older plate to be subducted.
What is a collision zone?
When two plates move towards each other.
How are fold mountains formed?
When two plates move towards each other, causing the sediments between them to squeeze and push upwards.
What is an earthquake?
Sudden and violent shaking of the ground as a result of movements within the Earth’s crust or volcanic action.
What is the focus of an earthquake?
The place where the earthquake originates from underground.
Define epicentre.
The point on the Earth’s surface that is directly above the focus.
What is liquefaction?
Process where sediments with high water content behave like a liquid when shaken by the earthquake.
What is a tsunami?
A large wave created by ocean flow displacement of landslide.
