Geo 1045 SG 2 Plate tectonics

How the study of seismic waves can tell us about the layering inside the earth

Seismic waves (P-waves and S-waves) behave differently through solids and liquids, helping map Earth's internal layers (crust, mantle, outer core, inner core).

Observations of Seafloor Spreading

Mid-Ocean Ridges, Sediment Thickness, and Age of Oceanic Crusts.

Lithosphere vs Asthenosphere

The lithosphere is solid and is composed of the crust and the upper portion of the mantle (these are the plates in plate tectonic).
The asthenosphere is plastic and is composed of the lower molten portion of the mantle (where convection occurs.)

Types of Plate Boundaries

Divergent, Convergent, and Transform.

Divergent Plate Boundary

Boundary in which 2 lithospheric plates move apart.

- Abyssal Plains, Mid-Ocean Ridges, Rift Valleys
- Volcanoes, Earthquakes

Convergent Plate Boundary

A boundary at which two plates move toward each other so that one plate sinks (subducts) beneath the other; only oceanic lithosphere can subduct.

- Subduction Zones, Trenches, Volcanic Arcs
- Volcanoes, Earthquakes

Transform Plate Boundary

A boundary at which one lithosphere plate slips laterally past another.

- Fracture Zone, Transform Fault
- No volcanoes, Earthquakes

Process Driving Plate Motion

Ridge Push and Slab Pull

Ridge Push

A process in which gravity causes the elevated lithosphere at a mid-ocean ridge axis to push on the lithosphere that lies farther from the axis, making it move away.

Explain the angle between the magnetic field and the surface of the Earth at a given location.

Equator: At the magnetic equator, the magnetic field is horizontal, and the inclination is 0 degrees. The magnetic field lines run parallel to the surface.

Poles: At the magnetic poles, the magnetic field is vertical, and the inclination is 90 degrees (positive at the north magnetic pole and negative at the south magnetic pole). The magnetic field lines plunge straight down into the Earth.

how the oceanic lithosphere changes from the mid-ocean ridge to subduction zones

Forms at mid-ocean ridges (hot, buoyant, young) and becomes cooler, denser, and thicker as it moves away; eventually subducts back into the mantle at subduction zones.