Plate tectonics Flashcards
Describe P-waves and S-waves, the similarities and differences.
P-waves(primary) are compressional body waves that travel through both a solid and liquid phase.
S-waves(secondary) are shear body waves(sinusoidal) that can only travel through solid and experience refraction.
What is the lithosphere? How do they move?
The crust and upper mantle, there are about 15-20, and move relative to each other.
What happens to the structure of the plate as they move?
The interior structure is rigid and does not change however deformation of the plate occurs at boundaries.
What evidence exists for tectonic plates?
Earthquake distribution.
Fossils across continents.
Give the plates of: UK Japan Hawaii Chile
Eurasia
Sits on the boundary of 4 plates, Eurasia,pacific and Philippines mainly.
Pacific plate
Nazca plate.
What sphere is below the lithosphere, and what is its relative strength compared to the lithosphere.
Where does it fit in relation to the subdivisions of the earth.
Asthenosphere, it is weaker but can flow.
It is in the mantle. the mantle is massive.
Explain a divergent plate boundary? Whats unique about the magma?
Ocean crust moves sideways, mantle undergoes decompression melting and the magma has gases dissolved that rise and cause it to crystalise to form new ocean crust.
Whats the temperature of the lithosphere compared to the mantle?
The lithosphere is the cold part of the mantle.
Explain convergent boundaries.
Two oceanic plates. The older one will cause the younger one to fracture and slowly sink, with the asthenosphere SLOWLY moving out of the way.
Can continents be subducted?
NO! They are too dense to fracture and sink, therefore are usually very old(3.8Ga!) whilst oceanic plates are continuously being created and destroyed.
What type of boundary is ocean-continent in terms of subduction?
Convergent.
Explain a transform boundary and give a famous example.
Plates move sideways to each other. Lithosphere is not destroyed. San Andreas fault(Pacific plate and NA plate).
What was the early model of plates moving?
What is considered now instead?
Convection cells.
Ridge-push and slab-pull.
