Class 1. Earth Structure and Plate Tectonics William Wilcock

1. 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 three 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 1 • Compare topography on Earth with other planets and interpret differences in tectonics – LAB 2

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

4. InternalStructure 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. 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 Heat Convection - Heating From Below Upwelling Plume Downwelling Plume Convection Important Thermal Boundary Layer } Conduction Important

8. You will commonly see mantle convection depicted in a simple manner, similar to this figure. This depiction is reasonable at subduction zones but wrong at mid-ocean ridges. A simplistic model of mantle convection and plate tectonics (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. 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