Class 1: Plate Tectonics Review Today’s topics: Earth’s compositional layers Plate tectonics:...

Class 1: Plate Tectonics Review

Today’s topics: Earth’s compositional layers Plate tectonics: theory & actions

Earth’s Compositional LayersAtmosphere & Hydrosphere

Crust

Mantle

Core

Earth’s Atmosphere & Hydrosphere

Earth’s Crust

more dense

relatively light

CRUST

Earth’s Mantle

MANTLEmore densethan crust

CRUST

Earth’s Core

highestdensity

CRUST

MANTLE

CORE

Earth’s Magnetic Field

rocky core

Earth

Requirements for magnetic field: 1. rotation

2. heat flow, convecting fluid3. a mobile conductor (iron or metallic hydrogen)

Global Earthquake Locations

Global Volcano Locations

Linking Observations

Continental Drift

Continental Drift (movie)

Ages of the Ocean Floor

Ma = Million years ago

1 billion years = 1 Gyr1 million years = 1 Myr

1 thousand years = 1 kyr

Heat Flow

Warm colors = higher heat flow

Cool colors = lower heat flow

high atocean ridges

Global Topography and Bathymetry

oceanridges

The Puzzle Solved…..

earthquake locations volcano locations

sea floor age sea floor bathymetry

+ heat flow too!

Earth’s Tectonic Plates

Earth’s Tectonic Plates (movie)

Lithosphere & Asthenosphere

Plate Boundaries

Divergent Plate Boundaries

Seafloor Spreading (movie)

Convergent Plate Boundaries

1 2

3

Seafloor Subduction (movie)

Transform Plate Boundary

strike-slipfaulting

Transform Faulting (movie)

Plate Boundaries

Hotspots

Hot Spots

hot spot trail

Hot (not molten) rising plume

lithosphere

Direction of plate Direction of plate motionmotion

Formation of Island Chains

V1

V1

melting at base of crust

V1

Formation of Island Chains (movie)

Example: The Hawaiian Chain

Fixedhot spot

• Earth’s crust is divided into plates• Plates move relative to one another at 1-15 cm/yr• Plate interiors are largely undisturbed• Deformation is concentrated at plate boundaries

Consequences:• Plate tectonics constantly change Earth’s surface• Earthquakes occur mostly at plate boundaries• Volcanoes occur mostly at plate boundaries

Basic Premise of Plate Tectonics

1. Examine volcanic rocks Q: what was the source for magma?

How do we explore Earth’s interior?

2. Observe seismic waves from earthquakes Q: where are the layers, what are their densities?

3. Examine meteorites Q: what are they made of? like the core?

4. Existence and behavior of geomagnetic field Q: what is the core doing?

• Satellites 1 (Moon)• Size (radius) 6378 km• Bulk density 5.5 g/cm3 (4.1 g/cm3uncompressed)

• Surface gravity 9.8 m/s2

• Tectonism, volcanism yes (today)• Rotation 1 day• Orbit 365.25 days• Atmosphere 78% N2, 21% O2

• Surface pressure 1 atm• Surface temperature 20°C (diurnal, seasonal changes)

• Plate tectonics yes• Water yes

Earth