Download The Solar System

“Our” Earth
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
• constantly moving/floating (116cm/year) on the plastic part of the
mantle because of convection currents
in the soft rock underneath them
–this is called continental drift
Plate Boundaries
• Divergent boundaries
– plates move apart
– Mid-ocean ridges are mountains created by
the rising lava
• Divergent Boundary
Mid-ocean ridges
• Convergent boundaries
– plates come together
– can develop chains of volcanoes,
mountains, and earthquakes
• Continental Drift - Tetrionic Plates
– subduction is where the denser plate dives
under another
• Juan de Fuca plate is diving under the
North American plate (this is not good)
• Animation of Earthquake and Tsunami in Sumatra
• Stuck in tsunami
For most recent EQ -- http://www.pnsn.org/recenteqs/latest.htm
Earthquakes
• energy is released as
plates slip along a fault
line
• 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;
Built to withstand 200 mph winds and an
earthquake of up to 9.5 magnitude.
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
– causes the most damage because of a
circular motion caused by up and down
AND back and forth motion
Weathering and Erosion - breaking
rocks apart
• Physical (mechanical) weathering
– glaciers moving, water (ice) expanding, wind,
and plant roots
– erosion: wind and water can loosen and move
sediment
– deposition: the sediment then builds up
somewhere else
• Chemical weathering
– O, H2O, and CO2 chemically react with many
minerals forming new compounds