Introduction to the earths interior

1 Earth’s internal heat engine.2 Earth’s magnetic field.. 3 reasons for internal heat:Earth’s internal heat engine 1 from impact during Earth formation 2 radioactive decay of uranium, th

1) Earth’s internal heat engine.

2) Earth’s magnetic field

3) Intro to

Seismology:

Tools for seeing into the Earth’s interior

(Chaps 2-4)

TODAY’s LECTURE:

Convection in the Mantle Drives Plate Tectonics! But how?

3 reasons for internal heat:

Earth’s internal heat engine

1) from impact during Earth formation

2) radioactive decay of uranium, thorium, potassium 3) heat released as inner core forms

Ways to transfer heat:

1) conduction - motion of atoms

2) convection - mass movement of material

Defined as the mass of a

material, per unit volume.

Usually given in grams per

cubic centimeter (g/cm3).

For comparison, the density

of water is 1.0 g /cm3

.

Earth’s internal heat engine

Hot materials are less dense and rise.

Convecting materials in the Earth’s mantle originate deep, near the core-mantle boundary

Most heat from the deep interior is transferred

to the shallow mantle by buoyant masses of hot, low density material called “plumes”.

Hawaiian Islands

Plumes Create Volcanic Hotspots

Earth’s internal heat engine

Earth’s internal heat engine

See: MantleConvection.MOV

Heat of the upper mantle sets up shallow convection cells that drive plate motions.

There are Three Basic Plate Margin Types:

Can You Identify Them?

See Video:

EarthOceanFloors.MOV

Consequences of Plate Motions: Mountain Building

Volcanic Activity

Mt Mayon, Philippines

Consequences of Plate Motions: Earthquakes!

Convection Also Drives Deep Seafloor Hydrothermal Systems

The magnetic field is generated by an organized flow of electrons in the molten outer core.

Earth’s magnetic field:

Earth’s magnetic field is a dipole with north and south ends of opposing polarity The magnetic poles and

geographic (rotational) pole are offset by 23.50

Earth-Sun Interactions:

(See: Bio_North_America.MOV

& Aurora.Mov)

Earth’s magnetic field:

Lines of magnetic force are

~parallel to the Earth’s surface at the equator, but are

vertically at the poles.

Earth’s magnetic field

Naturally-occurring

magnetic mineral

grains, like the

mineral magnetite,

act as tiny bar

magnets and become

oriented parallel to

the field lines of the

Earth’s magnetic field

Moon:

No magnetic field

No molten outer core

MARS:

Had a magnetic field

early in its history, but not today How do we know?

Remnant magnetism!

Magnetic reversals are recorded in igneous rocks by the remnant field orientations

frozen into by the magnetic minerals (e.g magnetite) that crystallize from magma as

it cools.

Magnetic reversals can be dated!

This is accomplished by using radiometric dating methods to date igneous rocks that preserve the

remnant magnetism.