1. The crust sits directly above the lithosphere as a separate layer. a. True b.

Question

1. The crust sits directly above the lithosphere as a separate layer. a. True b. False

2. Where is ocean crust created? a. Subduction zones b. Mid-ocean ridges c. Transform boundaries d. In Alaska

3. Magma is generally too hot to allow iron to move in alignment with the magnetic field. Magma needs to cool first. a. True b. False

4. Which process is responsible for tectonic plate motion? a. Convection in the asthenosphere b. Slab pull during subduction c. Ridge push during sea-floor spreading d. All of the above

5. What type of plate boundary is located off the coast of Oregon? a. Transform boundary b. Ocean-Ocean convergent boundary c. Ocean-Continent convergent boundary d. Divergent boundary e. Continent-Continent convergent boundary

Explanation / Answer

1. b. False.  

Explanaion: The lithosphere is also the crust plus the uppermost part of the mantle. The solid mantle above the asthenosphere, plus the crust above that, together makes lithosphere.

2. b. Mid-oceanic ridges

Explanaion: Oceanic crust is  created at mid-ocean ridges when tectonic plates diverge and magma rises into the upper mantle and crust. At a subduction zone and transform boundaries, the oceanic crust usually sinks and get destroyed into the mantle beneath continental crust which are lighter than the dense oceanic crust.

3. a. True

Explanation: The magma is too hot and has temperature between 700 and 1300 degrees Celsius. But we also know that the Curie temperature of iron is at 770 degrees Celsius and it loses magnetism above that temperature. Since its too hot, magma almost never can be magnetic.So there can't be any magnetism for iron and nickel that is this hot.

4. d. All the above

Explanation: Convection currents in asthenosphere drive plate tectonics. From the radioactive decay of elements, heat is generated deep in the interior of the Earth and it creates magma in the aesthenosphere. As hot magma rises to the surface at spreading ridges and forms new crust usually seen in ocean tectonic, the new crust pushes the rest of a plate out of its way and this is known as ridge push. At subduction zones, old parts of a plate are likely to sink down into the mantle because they are colder and thicker than the warm mantle material underneath them and the process is called slab pull.

All these there processes lead to the motion of tectonic plates

5. c. Ocean-Continent convergent boundary

Explanation: Along the Oregon coast, a tectonic plate called Juan de Fuca Plate is generated from the Juan de Fuca Ridge and is subducting under the western side of the North American Plate at the Cascadia subduction zone. Due the convergence of the ocean boundary beneath continent boundary, it has let to a history of earthquake and tsunami events which are highly life threatening in nature.

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