Match each term to its description.

1. the earths outermost layer
2. the firm layer between the crust and the asthenosphere
3. the metallic layer at the earth's center
4. the semi solid layer between the top layer and the upper mantle
5. the hottest part of the mantle
6. the layer surrounding the inner core
7. the layer between the asthenosphere an lower mantle

a. crust
b. inner
c. core
d. lower mantle
e. asthenosphere
f. upper mantle
g. top layer
h. outer core

1. The earths outermost layer
This would be the Crust!

2. The firm layer between the crust and the asthenosphere 
The only option left that makes sense is "top level" altought the word is often used to refer to the Crust, too

3. The metallic layer at the earth's center
This is the core

4. The semi solid layer between the top layer and the upper mantle
This would be the asthenosphere!

5. The hottest part of the mantle
This would be the lower mantle - as the closer to the core, the warmer!

6. The layer surrounding the inner core
Immediately around the inner core is the outer core - as the name would suggest!

7. The layer between the asthenosphere an lower mantle
This is the Upper mantle!

Geothermic gradient is the rate of increasing temperature with respect to increasing the depth in the earths interior. away from tech tonic plates boundaries, it is about 25-40 c/km (72-87 degrees f/mi) of depth near the surface in most of the world.