Tectonic plates Flashcards
The lithosphere is broken into…
seven major and six minor interlocking tectonic plates.
Each plate consists of…
the crust and portion of the asthenosphere.
Both oceanic and continental crust is less…
dense than the underlying upper mantle, so they flow.
Oceanic crust is mainly formed of…
basalt and it is known as SIMA=silica + magnesium
Oceanic crust is being constantly…
destroyed or created.
Continental crust is mainly formed of…
granite and it is known as SIAL=silica + aluminium
The continental crust is thinnest in…
areas like Rift Valleys of East Africa.
Sedimentary deposits are found at…
the boundaries between the continental and oceanic crust.
Isostacy is the ability…
of plates to rise or sink.
Isostacy occurs because…
the plates float on the top of the mantle. When the crust gains weight due to glaciations, it deforms and the crust sinks deeper.
Isostatic rebound is when…
the crust becomes more buoyant and floats higher in the mantle.
There is great instability and…
pressure at each plate margin.
Convection currents are mainly located in the…
asthenosphere.
Convection currents are driven by…
the heat exchange between the core and the upper zones of the mantle.
Colder, denser material…
sinks into the mantle and warmer, less dense material rises and spreads laterally.
The lateral movement caused by…
the convection currents move the plates.
Slab pull is the process caused by…
heavy, cold edges of plates are subducted back to the mantle, pulling the rest of the plate along.
Subduction is…
the reabsorption of cold and dense crust back to the mantle.
Ridge push occurs when…
the rising and intruding material forces the plates apart and new crust is formed.
A ridge is formed…
where the plates move apart.
A trench is formed…
where the crust is subducted.
Tectonic hazards can be predicted using:
- seismology
- ground deformation
- environmental change
Seismologists are regularly:
- mapping plate boundaries
- monitoring and measuring earthquakes/volcanoes
- study ground deformation in a crust (isostatic change)
Key monitoring countries:
- Iceland
- Japan
- Hawai
20 per cent of volcanoes come from…
hot spots-strong plumes of magma within a plate.
