Question

owen (rmc754) - web hmwk 1 - earths energy - mullins - (444)
2
earths core is probably

1. composed of mostly iron and nickel.
2. hollow.
3. composed of rock with high silica content.
4. molten throughout.
5. composed of potassium and aluminium-rich silicates.

009 3.0 points
which of the following statements about the asthenosphere is not true?

1. it behaves plastically.
2. it is a rigid rock layer.
3. it has the same composition as the lower mantle.
4. it lies beneath the lithosphere.
5. it acts like a lubricating layer allowing plates to move.

010 3.0 points
the ocean crust is composed mostly of

1. peridotite.
2. sial.
3. basalt.
4. granite.
5. gneiss.

011 3.0 points
the majority of volcanoes occur along

1. oceanic-oceanic convergent plate margins.
2. divergent plate margins above sea level.
3. all of these
4. divergent plate margins below sea level.

012 3.0 points
the thickness of earths crust varies because of
i) variations in composition.
ii) variations in density.
iii) variations in temperature.

1. i & ii only
2. ii only
3. iii only
4. i only
5. i, ii, & iii

013 3.0 points
one of the most general conclusions to be drawn from plate tectonic theory is that

1. earths geography has continually changed.
2. the ocean basins are continually enlarging.
3. earth is slowly shrinking.
4. earth is continually losing heat.
5. earth is slowly expanding.

014 3.0 points
in plate tectonic theory, the lithosphere

Explanation:

Question 009 (Which of the following statements about the asthenosphere is not true?)

The asthenosphere is a layer of the Earth's mantle below the lithosphere. It behaves plastically (so statement 1 is true), has the same composition as the lower mantle (statement 3 is true), lies beneath the lithosphere (statement 4 is true), and acts as a lubricating layer for plate movement (statement 5 is true). A rigid rock layer is the lithosphere, not the asthenosphere, so statement 2 is not true.

Oceanic crust is mainly composed of basalt. Peridotite is in the mantle, shale is a sedimentary rock (not main ocean crust), granite is continental crust, and gneiss is a metamorphic rock (not main ocean crust).

Crust thickness varies due to composition (continental crust is thicker, different composition than oceanic) and density (less dense continental crust "floats" higher, thicker). Temperature doesn't directly cause thickness variation. So I and II are correct.

Answer:

1. It is a rigid rock layer.

Question 010 (The ocean crust is composed mostly of)