internal Structure of Earth and Plate Tectonics

Earth Structure

1. inner core: solid metal (Fe, Ni)

• high temp and inner core is growing

2. outer core: liquid metal (Fe)

• earth’s magnetic field is generated (convection)

3. mantle: solid (Fe and Mg-rich silicates)

4. crust: outer rock layer (silicate)

• oceanic (denser, thinner, younger) vs. continental (less dense, thicker, older)

Moho Discontinuity

boundary between crust and the mantle

Lithosphere

cool, strong outermost layer of the earth (mantle + crust)

• broken into tectonic plates

Asthenosphere

hot, slowly flowing layer of weak rock below the lithosphere

• that allows for the tectonic plates to move

Heat vs. Temperature

temp: measure of hotness/coldness

heat: form of energy; the amount depends on temp change, amount, and type of material

how we know about internal structure

seismology (study of earthquakes and seismic wave movement)

Plate Tectonics

unifying theory explaining the distribution of continents/oceans/mountains, and location of earthquakes/volcanoes

• lithosphere is broken into plates that move relative to each other

• plates are created and destroyed (by heat transfer in the mantle)

Plate Movement

move very slowly (centimeters per year)

Seafloor Spreading

validity established by mapping oceanic ridge, paleomagnetic history of ocean basins, and dating volcanic rocks on the ocean floor

Paleomagnetism

earth’s magnetic field (like a dipole) permanently magnetizes some surface rocks at formation

• iron-bearing minerals orient parallel to the magnetic field below the Curie Temp

  • curie temp = temp below which minerals in a rock “lock in” a signature of earth’s magnetic field

  • evidence: original orientation, magnetic inclination (latitude of formation), and magnetic polarity (normal vs. reversed)