Geological Phenomena

The Continents Divide  It was long believed that the continents, mountains and oceans had not changed since the planet’s birth  In the early 20 th century Alfred Wegener suggested our continents were moving  Alfred Wegener = The Father of Continental Drift (Tectonic Plates)

Wegener’s Three Pieces of Evidence 1. Land masses seem to fit together like puzzle pieces 2. Mountain ranges on different continents have same age and rock composition 3. Fossils indicate land was once joined together

Pangaea Continent formed of all land masses, surrounded by a single ocean Continental Drift Pangea broke apart into large pieces that drifted to their present place

Plate Tectonics

Oceanic ridges Map of Underwater Relief

The Earth in Motion  The crust floats on the magma of the upper mantle  The crust is thin and cracked like an egg shell

Plate tectonics: movement of crust plates creating ridges, mountains and trenches (continental drift)  The crust is divided into seven large (tectonic) plates and a few smaller ones  Cracks usually occur where crust is thinnest (under water)

 Convection currents in the magma cause the tectonic plates of the crust to move.  Convection currents: caused by the rising of hot matter and the sinking of cooling matter. Convection – How the Plates Move

 These plates move approx. 1-20cm/year  Slowly the plate move towards each other, move apart from each other or slide past each other Convection – How the Plates Move

Types of Plate Movement

Subduction zone: area where one plate goes underneath another (converging)  Usually the plate under the ocean pushes under the continental plates. Much volcanic and earthquake activity Trench formation

Marianas Trench

Mid oceanic ridge: is an underwater mountain range where the plates are being pulled apart (Diverging)

Transform Fault

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Orogenesis Making Mountains

Orogenisis: when two continents collide and fold to create mountains Mountain: a landform with steep slopes and an altitude of at least 600m Example: Himalayas, Alps

Continental Collisions

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Volcanoes The Wrath of Vulcan

Parts of a volcano

Volcanic Eruptions  Volcanic eruptions can occur where plates collide or pull apart  In Subduction zones: Oceanic plate sinks under a continental plate and enters the mantle, it melts and is transformed into magma. The magma strives to rise to the surface (CO2 gas bubbles trying to escape)

Geysers Magma heats up underground bodies of water. The water rises to the surface and jets out of cracks in the land.

Volcano Video Clips    

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Earthquakes

Earthquakes: violent shaking of the earth (shock waves) produced by the friction between tectonic plates  Occur when built up tension between two tectonic plates is suddenly released  May happen in one of 3 ways  Thrust fault  Normal fault  Slip fault

 The resulting shock wave (seismic wave) produced can flatten entire towns in seconds   Or, if they occur underwater, can cause tidal waves or tsunamis

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Areas along the tectonic plates are most affected by volcanoes and earthquakes (Includes the Ring of Fire)

Memory Check Page 331