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1 Plate Tectonics Notes Geology – the study of the Earth and its processes.

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Presentation on theme: "1 Plate Tectonics Notes Geology – the study of the Earth and its processes."— Presentation transcript:

1 1 Plate Tectonics Notes Geology – the study of the Earth and its processes

2 2 The Earth’s Layers Scientists study seismic (earthquake) waves and volcanic explosions to learn about the Earth’s interior. Crust Mantle Outer Core Inner Core

3 3  Crust –outermost layer –thinnest layer –the layer we live on –divided into pieces, called tectonic plates –two types: continental and oceanic crust  Mantle –thickest layer –“flows” and allows the tectonic plates to move on top –primarily magma The Earth’s Layers cont…

4 4  Outer Core –liquid  Inner Core –solid –dense, high pressure layer at the center of the earth The Earth’s Layers cont… Core is made primarily of iron and some nickel

5 5 Alfred Wegener 1912 - proposed that all the continents were once joined as a single landmass –he called this “supercontinent” Pangaea –stated the continents have separated and collided as they have moved over millions of years –called his theory “continental drift”

6 Continental Drift Slide does not need to be copied 6

7 Wegener’s 5 major pieces of Evidence: 1. Continents (esp. South America & Africa) seem to fit together like pieces of a puzzle 2. Matching fossils occur on east coast of S. America & west coast of Africa 3. Matching folded mountain belts on coasts of S. America & Africa 7

8 Evidence cont… 4. Evidence of ancient climates show landmasses were once located elsewhere -Ex: glaciers in Africa ! 5. Data for latitudes & longitudes of locations is changing 8

9 9 Wegener is debated  Other scientists argued that the continents could not just plow through the oceans  Later evidence revealed Wegener was correct – he just didn’t have the technology to prove how the continents had moved

10 Modern Theory = Plate Tectonics  The crust is made up of about a dozen major, moving plates and several smaller plates  Plates can contain: –land = continental crust –ocean = oceanic crust –Both ! 10

11 Modern Evidence from the Oceans Scientists mapping the ocean floor found:  Underwater mountain chains  Ridges where the sea floor was actually spreading at sites called ridges  Some oceans were growing wider from the middle  Fossils and other materials are moving apart on either side of ridges  Newer, younger crust was being created by magma at the ridges 11

12 12  Magnetic measurements of the crust  Polarity (magnetic north vs. south) changes every so many thousand years  Magnetic rocks on the ocean floor show reversals  Rocks are in equal bands on either side of the mid-ocean ridges Modern Evidence cont…

13 13 What Moves the Plates?  Convection currents are created as heated rock rises to the surface, cools, and sinks again.  These currents carry the plates as if they are on a conveyor belt in conveyor belt in a process called a process called “slab pull.” “slab pull.”

14 14 Two different plates meet at a boundary. There are 3 types of plate boundaries: 1.Convergent = where plates collide 2.Divergent = where plates are move apart 3.Transform = where plates move up against one another

15 15 Convergent Boundaries:  When these 2 pieces of crust collide, they buckle and push upwards, forming mountains = uplift occurs  Ex: Himalayas & Mount Everest Type 1: continental / continental

16 16 continental crust to draw & label: Uplifted mountains continental crust

17 17  Oceanic is denser, so it sinks at the trench between the plates = called the subduction zone  The melting of the oceanic crust forms new magma which is less dense than surrounding rock, so it rises, forming volcanoes  Ex: Mt. St. Helens Type 2: continental / oceanic 17

18 18 continental crust to draw & label: oceanic crust trench melting volcanoes the mantle magma

19 19  The denser plate is subducted / sinks.  The melting of the crust forms new magma which will rise above the denser rock – as it cools, it may pile up to it may pile up to form land form land  Ex: Hawaiian Islands & Japan Islands & Japan Type 3: oceanic / oceanic

20 20 to draw & label: oceanic crust trench melting land & volcanoes the mantle magma oceanic crust

21 21 Hot Spots  In several places on earth, hot magma moves upwards through the crust  As a plate moves over this source of magma, volcanoes form at the hot spot.  As the plate continues to move, continues to move, a chain of volcanoes a chain of volcanoes of differing ages of differing ages forms forms

22 22 Divergent Boundaries:  The area where 2 plates are moving away from one another is called a rift zone.  Magma will rise up to fill the gap, cool, and harden to form new crust.  When this happens in the ocean, the process is called sea-floor spreading.

23 23 Ex: Mid-ocean ridge in the Atlantic – note: the youngest crust will be found in these areas Ex: Great Rift Valley in Africa – note: the inland sea that resulted 23

24 24 to draw & label: oceanic crust the mantle magma oceanic crust mid-ocean ridge sea-floor spreading

25 25 to draw & label: continental crust subsidence continental crust rift zone step 1 step 2 inland sea

26 26 Transform Boundaries:  Two plates may grind and jerk as they slide past one another.  The boundary where they meet is called a fault line.  The stressful movement often results in earthquakes.

27 27 Ex: San Andreas Fault Transform Boundary to draw & label:

28 28 continent ocean A B C D 1.Feature _____ is an ocean trench. 2.Feature _____ is undergoing subduction. 3.Feature _____ is part of the continental crust. 4.Feature _____ is part of the mantle. 5.Feature _____ is part of the oceanic crust. For discussion:

29 29 The “Ring of Fire” - A large number of the world’s volcanoes and earthquakes occur around the edges of the Pacific plate For discussion:

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