“Our” Earth

Earth’s Interior• Crust– 5 km – 70 km thick– made mostly of rock (Si and O)

• Mantle– about 2,900 km thick– mostly solid but “softer” towards the middle (Mg,

Fe, O, and Si)• Core– made mostly out of Fe and Ni• Outer Core– liquid/ hot molten metal

• Inner core– very hot but solid because of the pressure

Plate Tectonics• Tectonic plates – large pieces of the crust and part of the

mantle called the lithosphere• seven very large ones and lots of small

ones• are constantly moving/floating

(1-16cm/year) on the plastic part of the mantle because of convection currents in the soft rock underneath them–this is called continental drift

• probably once all connected in a super-continent called Pangea

Plate Boundaries• Divergent boundaries– plates move apart –Mid-ocean ridges are mountains created by

the rising lava

Mid-ocean ridges

• Convergent boundaries– plates come together– can develop chains of volcanoes,

mountains, and earthquakes– subduction is where the denser plate dives

under another• Juan de Fuca plate is diving under the

North American plate (this is not good)

For most recent EQ -- http://www.pnsn.org/recenteqs/latest.htm

Earthquakes• energy is released as a

plates slip along a fault line (crack in the Earth created when plates/rocks move)

• the focus is where the slippage occurs

• the epicenter is the point on the surface above the focus

• measured using the Richter Scale• each number increased on the scale is

about 10 times the amount of ground shaking and 30 times more energy

- the building can withstand winds and typhoons of up to 200km/h(with the top swaying by a maximum of 75cm/0.3inches)

and earthquakes of up to 7 on the Richter scale;

Earthquake Waves• Primary / Longitudinal / P waves – fastest waves– travel out in all directions from the epicenter– compress the earth’s crust

• Secondary / Transverse / S waves– slower than P waves– travel up and down– travel out in all directions from the

epicenter

• Surface waves:–move only across the earth’s surface– cause the most damage because of a

circular motion caused by up and down AND back and forth motion