1.0 Processes within Earth’s crust cause natural events

Earth’s plates

Facts  Rocks that form the plates under the continents are lighter than those found under the ocean  The ocean floor is made up of ridges (mountains) and trenches (valleys)

Theory of Plate Tectonics  The lithosphere (crust + mantle) are made up of large areas called plates  Earthquakes and volcanoes tend to more common where plates meet

Convection and Earth’s plates  What makes the Earth’s plates move?  CONVECTION  Where would the required heat come from??

What happens when they meet?  Edges of the plates are called ‘boundaries’  Diverging Boundary  When plates are moving apart. At these boundaries lava flows from the ridge and forms new crust  Sometimes these are big enough to be seen from the ocean’s surface, like those that formed Iceland

 Converging boundary  Plates come together  This causes earthquakes and volcanoes or mountains typically form nearby and trenches form at the boundary  Another kind is where the plates crush together to form mountain ranges (SK mountains 1.8 b.y.a)

You find……………… 1. What is an earthquake? 2. Why does it to happen? 3. Where do they occur? 4. How are earthquakes measured? 5. Who predicts earthquakes (and what do they do with this information?) With remaining time?? Discover a past earthquake- where was it, how strong, what was the damage?

What?  May 15, 1909, the largest earthquake in SK was recorded at 5.5 on the richter scale

Terminology  Faults- cracks in the Earth’s surface where movement occurs (different from boundaries)  Focus- place that rocks break under the surface in an earthquake  Seismic waves- earthquake waves  Epicenter- point on the surface above the focus  Richter Scale- measures earthquakes  Seismograph- measures and records motion made by earthquakes

Mountains  Mountain ranges are a series of mountains  A mountain is part of the Earth’s crust that is much higher than the rest of the land  Most are formed by folding or faulting

Folding  Folding can only happen when rocks were softened by heat and pressure within the crust  Think back to where mountains tended to form, what forces here would have caused the rocks to soften?

Activity/ Demo  Folded Mountains

Building Mountains  Mountains are formed by folding, faulting and volcanic activity  Folding- colliding plates cause heat and pressure, softening the rock and making it ‘wrinkle’. This forces the rock to be pushed upwards forming mountains  Fault- made by the shifting of faults in the crust  /module10swf.swf /module10swf.swf