GEO 3.1 EARTHQUAKE AND VOLCANO Flashcards
epicentre
The point on the Earth’s surface vertically above the focus of an earthquake
earthquake focus
The position within the Earth where an earthquake occurs.
Name the three types of movements of plate boundaries.
- Convergent
- Divergent
- Transform
Convergent + example
when two plates are pushing toward each other
e.g. the boundary between the Eurasian plate and the Indian plate at the Himalayas
Conservative plate margin
A plate margin where two plates slide past each other and no plate is either created or destroyed.
Type of stress : shearing
Constructive plate margin
A plate margin where two plates diverge and new oceanic plate is created in the gap.
Type of stress: tension
Convection currents
Currents in liquids and gases caused by heating. Heated material becomes less dense and
rises.
It then diverges, cools and descends – forming a series of circulation cells.
Crust
The outer layer of the Earth (between 6 and 90 km thick), which has a different composition to the
layer below
Destructive plate margin
A plate margin where two plates converge and one is destroyed (by being subducted beneath the other plate and melting).
Type of stress: compression
Fault
A crack in the rocks of the Earth’s crust where the rocks move and are displaced
Fold mountains
Long ranges of mountains formed by the compression and crumpling of rock layers, e.g. the Himalayas.
Mantle
The middle layer of the Earth between the crust and the core.
Mercalli Scale
A 12-point scale that
describes the effects of an
earthquake
Ocean ridge
A broad, high belt of ocean floor that is much higher than the surrounding area.
It is formed by volcanic activity at constructive plate
margins, e.g. the Mid-Atlantic Ridge.
Ocean trench
A long, narrow area of ocean floor (about 10 kilometres
deep), usually found at a destructive plate margin at the edge of an ocean.
