Tectonics and volcano formation Flashcards
What happens at a divergent plate boundary?
2 oceanic plates are present
magma rises and forces the edge of the plates upwards, forming a mid atlantic ridge
cracks and fissures release magma that rises, cools and solidifies forming volcanoes
What two kind of plates are present at a divergent plate boundary?
2 oceanic plates
What are the characteristics of an oceanic plate?
Thin - 7km
Young
Basalt
What are the characteristics of continental plates?
thick - up to 70km
older
granite
What are the two types of plates?
Oceanic and continental
True or false: ‘The asthenosphere moves the lithosphere’
True
Convection currents in the asthenosphere moves the lithosphere. (Hottest magma rises and cools and sinks)
Name the three types of plate boundaries
- Divergent
- Convergent
- Conservative
True or false: ‘at a divergent plate boundary the plates are moving away from each other’
true
At a convergent plate boundary the two plates are moving:
a) towards each other
b) away from each other
c) sliding past each other
a) at a convergent plate boundary the plates are moving towards each other under compression
with 2 oceanic plates present at a convergent plate boundary, what would be formed?
Island arcs - volcanoes in the sea
two continental plates at a convergent plate boundary form…..
extremely high mountains e.g Himalayas
continent collision
What is continent collision?
2 continental plates at a convergent plate boundary
Forms extremely high mountains
What plates would be found to form smaller mountains such as the Andes
An oceanic subducting beneath a continental
What is a strike-strip fault?
2 plates sliding past each other in opposite directions (conservative plate boundary)
What happens to the end of a subducted plate?
It melts in the asthenosphere creating magma, this magma rises and creates a magma chamber
What is it called where two plates touch?
The Benioff zone
Which plate subducts beneath the other?
The oceanic crust subducts beneath the continental
OR if faced with two oceanic crusts at a convergent plate boundary
The older, cooler denser oceanic crust
What magma type is at the divergent plate boundary?
Basaltic
What is the silica content at a divergent plate boundary?
45-54% low
Is the magma runny or viscous at a divergent plate boundary?
Runny
T/F
The plate boundary that lets out gas most easily has explosive eruptions
False
With easy gas escape, the lower the explosivity
When gas builds up it becomes explosive
T/F
Rhyolitic magma type at a continental vs oceanic convergent plat boundary is rich in silica
True
>70% silica content
What is the magma type found at a hotspot?
Basaltic
What is the magma type found at a convergent oceanic oceanic plat boundary?
Andesitic
