Landforms associated With Plate Movements Flashcards
What are oceanic ridges?
The longest continuous uplifted features on the surface of the planet, they are formed when plates move apart in oceanic areas.
What is filled between the plates?
The space between the plates is filled with basaltic lava upwelling from below to form a ridge.
What are Rift valleys ?
Valleys form when plates move apart on continental areas. In East Africa, for example, the brittle crust fractures as sections of it move apart.
On Rift Valleys areas of crust do what?
Drop down between parallel faults to form the valley. An area between two parallel rift valleys forms an upstanding block, known as a Horst.
The line of the American rift is known as what?
Is thought to be an emergent plate boundary, the beginning of the formation of a new ocean as Eastern Africa splits away from the remainder of the continent.
What is a deep sea trench ?
Where oceanic and continental plates meet, the denser oceanic plate is forced under the lighter continental one.
The down warping of the oceanic plate forms a very deep part of the ocean known as a trench.
Give an example of a deep sea trench?
Off the western coast of South America, the Nazca Plate is subducted under the South American plate forming the peru- chile trench.
What is a island arc?
During subduction, the descending plate encounters hotter surroundings, and this is coupled with the heat generated from friction,begins to melt the plate.
As material is less dense than surrounding atmosphere, it rises to surface as Plutons of magma.
When plutons of magma reach the surface they form what?
Form complex,composite and explosive volcanos.
What’s happens if the eruptions take place off shore ?
A line of volcanic islands forms, these are known as island arcs. The Marianas Islands and Guam form a very good example, running parallel to the Marianas trench.
What are young fold mountains ?
The plates forming continental crusts have a much lower density, than the underlying layers, so there is not much subduction when such plates meet.
Plates move towards each other their edges& sediments between them are forced up into fold mountains.
As there is no volcanic activity is the formation of fold mountains, what happens ?
Material is also forced downwards to form deep mountain roots.
How was the Himalayas formed as an example of a fold mountain?
At indo- Australian plate it is moving northwards into the Eurasian plate.
Previous intervening ocean,known as the sea of Tethys, has had its sediments forced upwards in large over folds to form the Himalayas.
Process continues today.
Give another example of a fold mountain?
The Andes runs down the area where the Nazca Plate is being subducted beneath the lighter South American plate, this is a good example of molten magma rising from depth also gives rise to a number of explosive volcanoes in the Andes.
