Question

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.

Explanation:

Question 009

To determine the false statement about the asthenosphere:

• The asthenosphere is part of the upper mantle, behaves plastically (so statement 1 is true).
• It is not rigid; the rigid layer is the lithosphere (so statement 2 is false).
• It has the same composition as the lower mantle (statement 3 is true).
• It lies beneath the lithosphere (statement 4 is true).
• It acts as a lubricant for plate movement (statement 5 is true).

To find the main component of ocean crust:

• Peridotite is in the upper mantle.
• Sial is continental crust.
• Ocean crust is mainly basalt (a mafic igneous rock).
• Granite is continental crust.
• Gneiss is metamorphic, not main ocean crust.

Answer:

1. It is a rigid rock layer.

Question 010