Introduction to the earths interior

TODAY’s LECTURE:

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)




Convection in the Mantle Drives Plate Tectonics! But how?


Earth’s internal heat engine
3 reasons for internal heat:
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


Density:

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.
Cooler materials are denser and sink.



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”.


Plumes Create Volcanic Hotspots
Hawaiian Islands


Earth’s internal heat engine

Cold down-going
material
See: MantleUpwelling.MOV

Hot upwelling
Material
See: MantleDownwelling.MOV
.


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


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


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