radioactivity

Nuclear radioactivity: 

• Natural radioactivity; spontaneous emission of particles or energy from an unstable nucleus

• Discovered by becquerel

• Three types of radioactive decay

  • Alpha decay nucleus

  • Beta decay high energy electron

  • Gamma decay high energy electromagnetic radiation

Half life: the time it takes for something to decay to 50% of the sample 

decay products over time: determine half life and how much times has gone by

• Outermost layer of earth constantly repairs it self

• Rocks and melt to reform new, so then we cant tell the age of them

• Zircon: can tell the time of which the planet formed due to parts of it not decaying 

The earth interior:

• Crust (lithosphere) 0-100km

  • Mostly basalt and granite

• Upper mantle (asthenosphere) 100-200km

• Mantel ( molten) 200 km-3000 km

• Outer core (semisolid) 3000-5000 km

• Inner core (solid) Ni, Fe 5000 km and greater-6400 km in depth 

How do we know?

• P waves, primary wave or longitudinal waves are a pressure wave that travels through solids, liquids and gases when travels through different media or densities the wave may bend/be refracted

• S waves, secondary waves of elastic waves may travel through solids and semi solid, but not liquid

The interior of the earth:

• The molten rock underneath the crust of the earth circulates due to convection currents caused by the difference in temperatures between the earth's core and the outer layers

• The thermal energy is left from the earth's formation and the short lived radioactive elements

• This circulations cause two major effects on the planet

  • Couples with the earth fast rotations-dynamo theory

  • Plate tectonics 

Magnetic differences:

• Smaller planets cool faster thus halting most tectonic activity

  • Moon-small remnant field

  • Mercury-very small (about 1% of earth's magnetic field)

  • Venus-no (slow rotation in retrograde. dormant?)

  • Mars- small remnant (core)

According to the dynamo theory: a planet will have a strong magnetic field if it has a fast rotation and liquid core

Plate tectonics:

Diverging boundaries-when tectonic plates are driven apart by convection currents in the earth a divergent boundary is formed

<- icelandic rift and the mid atlantic ridge seafloor spreading