Plate margins and magma plumes Flashcards
How are ‘young’ fold mountains formed?
formed due to collisons/subductions
How old are ‘young’ fold mountains
generally 30-40 million years old
Give an example of ‘young’ fold mountins?
the Himalayas
Give an example of ‘old’ fold mountains?
The Cairngorms
Define syncline.
dip in mountains
Define anticline.
raise in mountains
What can a destructive plate margin also be called?
Convergent/ collision
What can a conservative plate margin also be called?
Transform
What can a constructive plate margin also be called?
Divergent
What happens when continental and continental plates collide?
fold mountains form
What happens when Oceanic and continental plates collide?
subduction
What happens when oceanic and oceanic plates collide?
subduction
What is the Benioff zone?
An inclined zone in which many deep earthquakes occur, situated beneath a destructive plate boundary where oceanic crust begins to melt due to friction
What is an ocean trench?
A linear depression on the sea floor which runs parallel to the plate boundary and is caused by the subduction of one plate under another
What is an Accretionary wedge?
Scraped sediment
What is the plate margin at the Himalayas?
Collision plate margin
What plates are at the Himalayas?
Indo-Australian and Eurasian (both Continental)
What has formed at the Himalayas?
‘young’ fold mountians
How long is the fold mountain chain at the Himalayas?
2,400km long
What is the plate marigin at the Andes?
Destructive plate margin
What are the plates at the Andes?
Nazca (oceanic) and South American (continental)
What has formed at the Andes?
Ocean trench
How deep is the ocean trench at the Andes?
4000m deep
What is the plate margin at the Caribbean?
Destructive plate margin
What are the plates at the Caribbean?
Caribbean (oceanic) and North American (oceanic)
What has formed at the Caribbean?
Puerto Rico trench and the Island Arc chain
Give an example of a ridge,
Mid-Atlantic ridge
Give an example of an ocean trench.
Puerto Rico trench/ Mariana trench- Philippines
What plates are at the mid-Atlantic ridge?
Oceanic and Oceanic
How does a ridge form?
- convection currents pull the tow pieces of oceanic crust apart
- where the crust separates it leaves a thinner bit of lithosphere that rises
- the weakened crust allows magma to escape
- the lava builds up in layers to for a ridge
What are the characteristics of a ridge?
-Longest features on the planet
- transform faults at right angles to the plate boundary
What plates create a rift valley?
Continental and continental
What are the characteristics of a rift valley?
- triggered by plumes of magma
- normal (parallel) faults
- volcanoes
- lakes of valley floors
Define magma plumes.
Areas of high heat flow within the mantle
Give some characteristics of magma plumes.
- random distribution
- they occur on any plates (middle of plates or plate boundaries)
Give an example of a current hotspot.
Hawaii
How old is Hawaii hotspot?
less than 0.7 million years old
How long is the Hawaii island?
2,600km long
How far is Hawaii from the closest plate boundary?
3,200 km
How does volcanic hotspots form?
created as plumes of magma rise through the earths mantle
The oldest islands are _______ from the hotspot
furthest
Why do volcanic earthquakes occur?
generated by magma movement
Why do tectonic earthquakes occur?
because of structural weaknesses at the base of the volcanoes or within the crust below
What is basaltic lava?
- runny lava which allows gas to escape easily which leads to effusive eruptions
What is the temperature of basaltic lava?
over 1000 degrees Celsius
What is Andesitic lava?
sticky lava which traps gas
How does magma plums create a chain of islands?
- convection currents draws heat to a section of the lithosphere
- The mantle makes its way through the crust
- Volcanoes form as the magma escapes
- As the tectonic plates move over the hotspot the volcanoes move further away, reducing their levels of vulcancitity
- This process starts again with a new volcano forming
