1. Class 1. Earth Structure and Plate Tectonics William Wilcock
OCEAN/ESS 410
Class 1. Earth Structure and Plate Tectonics William Wilcock

2. Lecture/Lab Learning Goals
Know and be able to sketch the basic structure of the Earth (crust, lower/upper mantle, core).
Be able to describe the process of planetary differentiation
Be able to define plate tectonic theory and the 3 types of plate boundary
Understand the linkages between plate tectonics and mantle convection
Be able to identify tectonic features on a global scale map of topography/bathymetry (with or without seismicity) - LAB

3. Plate Tectonics fracture zone island arc trench trench MOR earthquakes
continental crust
ocean crust
earthquakes
magma
melt
Mantle
melt
Mantle
adiabatically rising mantle material
sediments, igneous crust & mantle

4. Internal Structure of the Earth. The Earth is a differentiated Planet

5. Planetary Differentiation - early in Earth’s history

6. The Earth as a Heat Engine
Heat generated by
Radioactivity (U, Th, K isotopes)
Solidification of Inner Core
Heat Lost from the Earth by
Mantle Convection

7. Heat Convection - Heating From Below}
Conduction
Important
Convection (or advection) refers to the transport of heat by motion in a liquid or a gas
It is a very efficient means to transport heat
Thermal Boundary Layer
Upwelling Plume
Downwelling Plume
Convection Important
Thermal Boundary Layer }
Conduction
Important

8. A simplistic model of mantle convection and plate tectonics
You will commonly see mantle convection depicted in a simple manner, similar to this figure.
This depiction is reasonable at subduction zones but not very accurate at mid-ocean ridges.
(figure from Earth by F. Press and R. Siever, 3rd. edition, 1982)

9. Heat Convection - Internal Heating
Thermal Boundary Layer
Convection in the Earth’s mantle is driven primarily (80-90%) by internal heating from the decay of long lived radioactive isotopes of potassium, uranium and thorium and not heat loss from the core (10-20%).
The pattern of convection for internal heating is different from bottom heating.
Broad Region of Diffuse Upwelling
Downwelling Plume

10. Many Aspects Mantle Convection in the Earth are Still Incompletely Understood
volcanic island chain
ocean crust
mid-ocean ridge
trench
island arc
cont.
crust
from Kellogg et al., 1999

11. Global Bathymetry
Sandwell and Smith

12. Plate Tectonic Theory
The Earth’s surface is made up of a number of a small number of rigid plates that move relative to one another. Deformation near the earth’s surface is concentrated along the boundaries between. Plates boundaries may be sites of
Divergence - oceanic spreading centers and rifts
Convergence - subduction zones and regions of continental collision
Motions that are orthogonal to the plate boundary - transform faults.

13. Tectonic Plates