Tectonics - types of plate boundaries

Question 1

DIVERGENT PLATE BOUNDARIES

Answer 1

constructive margins - plates move away
most clearly displayed at mid-ocean ridges
new oceanic crust is created, thinner and denser than continental plates
earthquakes tend to be small and frequent - low hazard risk as they do not typically trigger tsunamis

Question 2

CONVERGENT / TRANSFORM PLATE BOUNDARIES

Answer 2

destructive plate margins.
they generate some of the largest and most damaging earthquakes
oceanic plate subducts under continental plate
e.g. Japan 2011
volcanoes created due to subducting oceanic plate
SUBDUCTION ZONES e.g., the Pacific Ring of Fire

Question 3

CONVERGENT PLATE BOUNDARY

Answer 3

Lithosphere is neither created nor subducted
sites of extensive shallow focus earthquakes
e.g., San Andreas Fault, California - Pacific Plate, creates a zone of friction against the North American Plate

Question 4

formation of hotspot volcanoes - intraplate activity

Answer 4

1) heat from the mantle rises as a hot thermal plume
2) high heat and low pressure at the base of the lithosphere enable melting of the rock
3) molten magma rise through the cracks and vents, erupting to form active volcanoes on the surface
4) tectonic plates move over the stationary hotspot. the volcanoes become extinct and new ones form in their place

as oceanic volcanoes move away from the hotspot, they cool and subside, producing older islands, atolls and seamounts.
over long periods of time this can also create chains of volcanoes
EXAMPLE - Hawaiian Islands, 3700 miles long