1. Ocean Basin Bathymetry
Course Notes: 2.1

2. Profile of Ocean Bathy
Course Notes: 2.1

3. What’s “a”?
Course Notes: 2.1

4. What is the Lithosphere?
Course Notes: 2.2

5. What is the Lithosphere?
1. It is all the mat’l that moves with the migrating crustal surface.
2. It is all the mat’s that behaves as a solid on geologic time scales.
Both definitions establish lithospheric base as a rheological, not compositional boundary such as the moho is defined.
Since the main determinant of mantle rheology is temperature, we can place the base of the lithosphere at an isotherm. T = 1200 deg. C
Why? Because lab experiments show that above this temp, mantle materials deform sufficiently rapidly to be considered fluids on geological time scales.
Course Notes: 2.2

6. Conservation of Thermal Energy, a.k.a. The Heat Flow Problem
Blackboard derivation
Course Notes: 2.3

7. Evolution of Thermal Structure in Cooling Rock Column
Course Notes: 2.3

8. Why the droop?
The mean temp. of the lithosphere is cooler, and hence more dense, than the mantle.
This urge to sink increases with lithospheric thickness, which increases with time subjected to cooling.
Course Notes: 2.4 & 2.5

9. Oceans of Kansas
Course Notes: 2.5

10. Mono Lake – Problem 1 of Problem Set #1