1) Name the 5 lithospheric plates which are responsible for the Mid-Atlantic Ridge.

The standard answer is North American plate, South American plate, Eurasian plate, African plate, and Antarctic plate
I don't get the bolded part...in what way is the Antarctic plate responsible for Mid-Atlantic Ridge? Between Antarctic plate and which plate make up part of the Mid-Atlantic Ridge?

2) Name the lithospheric plate whose subduction is responsible for the longest mountain range on earth.

Originally the answer is Nazca plate, but a student in my class argues that mid-ocean ridges are the longest mountain range on earth and the teacher changes the answer to Pacific plate...this seems not to be making any sense to me. If I assume that the question is refering the longest mountain range on earth as the mid-ocean ridges instead of the Andes, the answer of Pacific plate is still not possible. First of all, the mid-ocean ridges aren't formed by subduction, but formed by divergence. Secondly, Pacific plate only includes part of the mid-ocean ridges that winds around the earth. What do you think is the appropriate answer?

3) Name the lithospheric plate which moves eastwards away from the African plate and name the resulting major geological feature as a result of the above mentioned plate separation.

I answered Arabian plate and the plate separation formed the Red Sea, but I got marked wrong for the second part, and the correct answer is East African Rift. Why? Isn't the East African Rift be way below the Arabian-African plate boundary? :confused:

Would someone like to discuss? :eek:

I got these questions from a test...I seriously don't understand the standard answers...can anyone help? I would appreciate!

The East African Rift Valley started forming about 8-10 million years ago, as a result of tension built up by the upwelling of a magma superplume under southern Africa. Eventually east africa will split away completely to form a large island with a long seaway to its west.

The East African Rift Valley started forming about 8-10 million years ago, as a result of tension built up by the upwelling of a magma superplume under southern Africa. Eventually east africa will split away completely to form a large island with a long seaway to its west.
Does any part of the East African Rift touches the Arabian-African plate boundary? I don't get the standard answer to question 3...

kingwinner, look at a map of east Africa, particularly the southern end of the Red Sea. You'll see an area named the Afar Triangle. That's an area of sea-floor that's been cut off from the sea by the growth of volcanoes across the mouth of the gulf. The East African Rift Zone is a classic triple boundary. There is the Rift Valley, going south into Africa. There is the Red Sea, which is the northwestern arm of the triangle. There is the southern coast of the Arabian peninsula, which is the northeastern arm. The Afar Triangle is where this junction splits in three, which explains why it used to be under water, and why the volcanism occurred that shut it off from the sea.

The Arabian Plate is being pushed in a northeasterly direction, on a collision course with Iran, which explains Iran's constant earthquakes. Eventually, ove the next few million years, Saudi Arabia and Iran will merge as the two plates are pushed together (because Iran can't get out of the way, obviously).

In the meantime, The Indian Plate will be pushed over to collide with Burma, over the next fifty million years from now. The East African Island will collide with south east asia about two hundred million years from now.

Thanks for your time for explaning, Xylene! :)

I have just spent half an hour reading in the Wikipedia and have found two key quotes explaning East African Rift.

"The [Red] sea occupies a part of the Great Rift Valley [i.e. East African Rift)]"

"It [East African Rift] has been created through the rifting and separation of the African and Arabian tectonic plates that began around 35 million years ago in the north, and by the ongoing separation of East Africa from the rest of Africa along the East African Rift, which began about 15 million years ago."

They match the standard answer to question 3 and I finally understand it now! The best answer to question 3 is, indeed, East African Rift. ;)

Can someone explain question 1 & 2?

For question 2, "Name the lithospheric plate whose subduction is responsible for the longest mountain range on earth"
By the word subduction, it is obviously referring the longest mountain range on earth as the Andes instead of the mid-ocean ridges, and the answer would be impossible to be Pacific plate, which is the standard answer given by my instructor, right?

The subduction of the Nazca Plate is responsible for the creation of the Andes.

Yes

well I have a question. Is it possible that due to convection currents, or
Global Warming, The solid outer mantle become more liquid? I have read that the aesthenosphere is becoming more liquid, I just wonder if the mantle will slip under the crust around the fixed axis of the central gyroscope core.
Since the core temperature has risen and there is now buldges in the earth crust near the equator etc.. can the outer mantle lose its adhesive grip and the plates slide?

protostar, what can happen due to GW is that when, say, Greenland loses its icecap, and all the ice slides off into the sea, Greenland is relieved of billions of tons of ice-mass. This has the immediate effect of the Greenland continent
rising up out of the sea as the aesthenospheric material slides back underneath. On average, ice will push down the land beneath it by about one third the depth of the ice--so 12000 feet of ice, like you can find on parts of Greenland, will depress the land by about 4000 feet. That's not to say of course that Greenland is suddenly going to rise the entire amount, but it will certainly bounce up by a considerable amount--100 metres immediately, perhaps, displacing water as it does so. Also, as the sea floors and crustal plates readjust to the new load, there will be earthquakes such as you've never experienced in your life before.

very interesting indeed, would that be considered a polar shift?

protostar: There are yet-to-be mapped convection currents that make some parts of the upper mantle more viscuous than others. In addition to this there are hot spots in certain areas that produce volcanic arcs and chains (Hawaii), small mountanous upliftings, or just are there. Then there are also direct magma protrusions from the core-mantle boundary straight up to the crust.

The Mid-Atlantic Rift Mountain Range is the longest mountain range in the world: not any in the Pacific. This involves the seperation of the the North and South American Plates from the Eurasian and African Plates.

"The Mid-Ocean Ridge is Earth's longest mountain range. The ridge circles the globe from the Arctic Ocean to the Atlantic Ocean passing into the Indian Ocean and crossing into the Pacific Ocean. This range is four times longer than the Andes, Rocky and Himalaya Mountains combined."
http://pao.cnmoc.navy.mil/educate/neptune/trivia/large.htm

The Ten Longest Mountain Ranges [on land]:
Andes: 4,500 miles
Rocky Mountains: 3,000 miles
Himalayas: 2,400 miles
Great Dividing Range: 2,250 miles
Transantarctic Mountains: 2,200 miles
Brazilian Coastal Range: 1,900 miles
Sumatra-Java Range: 1,800 miles
Aleutian Range: 1,650 miles
Tien Shan: 1,400 miles
New Guinea Range: 1,250 miles
http://www.santacruzpl.org/readyref/files/g-l/lngstmtn.shtml

However, in terms of historical plate tectonic mountain building, the Alpide Mountain Range (which extends from New Zealand, through the Himalayas, the Mediterranean, and out to the Atlantic) is probably the longest. Then if you look back farther in history when Pangaea was formed and then broke up, the Appalachians were probably even longer. They are not obviously still present in the Eastern U.S., but also have remnants in the Northeastern Atlantic and then way down the coast of Europe to Morroco. Then if you go back to the supercontinent Rodinia (50-600 mya)...?