Plate tectonics Flashcards
What is the most active on-land set of volcanoes present on earth
Pacific ring of fire
Plate tectonics definition
describes how the Earth’s lithosphere moves around
How many plates are there
7 major
6 minor
Which is the biggest plate
Pacific
example of a destructive plate boundary
Japan (continental) and Pacific (oceanic) - sea floor of Pacific plate is moving towards Japan at around 10 cm per year (Rothery, 2015) p.54
How deep can EQ be tracked to
700km
Example of a continent- continent collison
India colliding with Asia around 30 million years ago forming the Tibetan Plateau fringed to the south by the Himalayas
Ophiolite
slice of oceanic lithosphere which has escaped subduction and has been preserved on land
Divergent Plate Boundaries (constructive)
Where the two tectonic plates move apart allowing for new lithosphere to be formed
Example- Oceanic divergent plate boundary
Mid ocean ridges (MORs) - formed of gabbro - similar to basalt but cools slower
Example- Continental divergent plate boundary
Continental rift zones - e.g. East African Rift Zone
Convergent (destructive) plate boundary
Where two plates move towards each other with the denser, older plate, usually the continental plate, is subducted beneath the newer, less dens plate
Example- Oceanic- oceanic Convergent (destructive) plate boundary
Island Arcs- a chain of island which are parallel to a subduction zone
e.g. Allusion or Caribbean
Example- Oceanic- continental Convergent (destructive) plate boundary
Active continental margins
e.g. Andean continental margin or Cascade margin (Canada and USA)
Conservative Plate Boundary
where 2 plate slide past each other
Example- oceanic Conservative Plate Boundary
transform faults
Example- continental Conservative Plate Boundary
e.g. San Andres Fault
How much is the San Andres Fault moving per year
the South west side of the fault (pacific) is moving north west at an average of around 1 cm per year relative to the rest of north america (Rothery, 2015) p.64
Triple Junction
where 3 plates meet e.g. southern Chile - Nazca, South American and Antarctic Plates meet
What combination of plates CANNOT occur at a triple junction
TTT = 3 trenches
How many different combinations of plates can occur
16
R- ridge
T- trench
F- fault
What is the most common combination of tripe junction plates
RRR
Passive continental margins
not a plate boundary
e.g. edges of the Atlantic ocean
continental lithosphere is welded onto oceanic lithosphere with no relative motion between them - no treches, volcanoes and have a low seismicity
