Plate Movement Flashcards
Examples of convergent/destructive plate boundaries?
Nazca and South American plate
Examples of divergent/constructive plate boundaries?
East African Rift Valley and Mid Atlantic Ridge
Examples of conversant/collision plate boundaries?
Eurasian and indo Australian plate
Examples of conservative margins?
Caribbean/North American
Who provided the idea for the sea floor spreading and why?
Harry Hess.
He noticed the youngest rocks were in the middle eg. Iceland and that the oldest were near the USA and Canada. Also paleomagnetism provided evidence as we study the history of the changes to the earths magnetic field
What are conservative plates?
When two plates are travelling the same way but at different speeds. Friction builds up between them causing earthquakes
What are destructive plates?
When an oceanic plate meets a continental plate it subducts underneath it as it’s more dense. The oceanic plate melts due to heat from friction and the mantle. Increased pressure causes pressure in magma chambers and it erupts.
What are constructive plate margins?
When two plates move apart from eachother they allow magma to come in the middle which cools and solidifies causing a mini volcano under the water
What are fold mountains?
1) where an area of sea seperates two plates, sediments settle on the sea floor in depressions called geosynclines
2) when the two plates move towards eachother again the layers of sedimentary rock on the sea floor become crumpled and folded
3) eventually the sedimentary rock appears above sea level as a range of fold mountains
- examples include the alps, andies and Himalayas.
- happens near convergent or compressional boundaries
What are rift valleys?
A linear shaped lowland/valley that has been created between several highlands or mountain ranges created by the action of a geological rift or fault.
What is an ocean ridge?
General term for an underwater mountain system that consists of various mountain ranges, typically having a valley known as a rift running along it’s spine formed by plate tectonics.
What is a deep sea trench?
Any long, narrow, steep sided depression in the ocean bottom which occur the maximum oceanic depths (approximately 7,300 to more than 11,000 meters)
- formed between converging plates when one plate subducts under the other. Islands form parallel to the ocean trenches on the overriding plates
What is a hotspot?
Concentration of radioactive elements in the mantle cause a mantle plume to rise. This rises up under the lithosphere to heat into the plate above. This hot area under the crust is called a hot spot.
How are island arcs formed?
As the plates move, the volcanoes move with them, making them dormant and then extinct as they move away from the hotspot. The hotspots are static and so a new volcano is formed later.
What are sea mounts?
They are volcanoes that have been submerged and eroded under water/ a mountain on the ocean floor that does not reach the surface
