Geology question. 1 - The maps below show the surface of the Earth as viewed fro

Question

Geology question.

1 - The maps below show the surface of the Earth as viewed from the sky, at a convergent plate boundary which map best illustrates where volcanoes, marked with symbol, would be located? Oceanic Ocnic Trench Ridge Oceanic Oceanic Trench dge Rdge Ridge Trench 2 - If you could travel millions of years into the future, as sea floor spreading continues to form new oceanic lithosphere, how big would the planet Earth be? A. Smaller than today B. Larger than today C. Same size as today D.-We have no way of knowing 3 - How will continental lithosphere change as mountains are formed during collisions with another lithospheric plate? A. Continental lithospheric thickness will stay the same B. Continental lithospheric thickness will increase C. Continental lithospheric thickness will decrease

Explanation / Answer

Ans.

1. Map (c) is best suited for volcanoes.

Explanation - Volcanic activity occurs at mainly two types of plate boundaries: (1)mid-ocean ridges and (2)subduction zones.

At mid-ocean ridges, basaltic eruptions produce new sea-floor crust. These underwater eruptions don't produce big mountainous volcanoes, which is why they are often overlooked as the most volcanically active features on Earth. Commonly, basalt is erupted at mid-ocean ridges as blob-shaped "pillows."

At subduction zones, volcanoes are created on the overriding plate as melt from the subducting plate rises up through the mantle and crust.

2. (B) Larger than today's

Explanation - If new oceanic crust and lithosphere is continually being created at the oceanic ridges, the oceans should be expanding indefinitely, unless there were a mechanism to destroy the oceanic lithosphere.

3.Continental lithospheric thickness will decreases.

Explanation - When two continental plates collide neither plate can be subducted due to their high bouyancy. With this type of collision there are no features such as a subduction zone, trench or acretionary wedge. The collision of two continental plates occurs when a sea becomes narrower until both plates collide. After collision the oceanic lithosphere breaks off and sinks into the mantle. The subduction zone eventually becomes inactive The two continents become welded together as they are compressed together over time. The crust is thickened by the underthrusting of one continent under the other.

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