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1.1 Earth has several Layers.  Denser material sinks  Less dense material rises to the top.

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Presentation on theme: "1.1 Earth has several Layers.  Denser material sinks  Less dense material rises to the top."— Presentation transcript:

1 1.1 Earth has several Layers

2  Denser material sinks  Less dense material rises to the top

3 Crust: Thick layer of cool rock, surrounding earth. There are 2 types: oceanic and continental Mantle: Earth’s thickest layer, 1700 miles thick, hot rock, less dense than core Outer Core: Layer of liquid metal that surrounds inner core Inner Core: Ball of solid, hot metal


5  Lithosphere: most rigid of the layers, contains the outermost part of the mantle, and the crust  Asthenosphere: layer of hotter, softer rock in the upper mantle


7  Tectonic plates fit together like a jigsaw puzzle  Contain both continental crust and oceanic crust

8 1.2 Continents Change over Time


10  Continental Drift  Hypothesis proposed by Alfred Wegener in 1912Alfred Wegener  Earth’s continents were once joined in a single landmass and gradually moved apart.

11  Fossils: mesosaurus found in South America & Western Africa – not found anywhere else!  Climate: evidence of change: Warm weather plants in Greenland, glacial evidence in South Africa  Geology: rocks from Brazil match those of Western Africa, Limestone of Appalachian mountains matches Scotland’s highlands

12  Pangaea: Greek meaning “all lands” Pangaea:  Giant continent that reached from pole to pole and covered area where Africa lies today


14  In the mid 1900’s scientists proved that tectonic plates move.  Built upon Wegener’s ideas.

15  Mid Ocean Ridges: huge underwater mountain ranges Mid Ocean Ridges ◦ Sea Floor Spreading – ridges form along cracks in the crust, molten rock rises through the cracks making new crust ◦ Age of sea floor – sea floor is youngest at the ridges, older farther away ◦ Ocean trenches – deep canyons where the sea floor is sinking into asthenosphere.

16  Convection: energy transfer by the movement of material  Convection current: sinking and rising motion that transfers heat in a material

17 Convection

18  Theory of plate tectonics: Earth’s lithosphere is made of huge plates that move over the surface of the earth.

19 1.3: Plates move apart

20  Divergent boundaries: occurs where plates move apart – most are found in the ocean  Convergent boundaries: occurs where plates push together  Transform boundaries: occurs where plates scrape past each other

21  AKA spreading centers  Rift valley: deep valley formed as tectonic plates move apart, as a long a mid-ocean ridge

22  Mid-ocean ridges are the longest chains of mountains on Earth  Mid-Atlantic ridge world’s longest mountain range

23  Earth’s magnetic poles switch places, called magnetic reversals  How stuff worksstuff

24  Like the sea floor, continents can split apart at a divergent boundary  Great Rift Valley

25  View plate boundariesplate boundaries

26  Hot spot: heated rock rising in thin columns from the Earth’s mantle. Hot spot:  Hawaiian islands

27 1.4: Plates converge of scrape past each other

28  Subduction: when one plate sinks beneath another  Oceanic crust: crust under ocean floor - more dense  Continental crust: crust forming the continents – less dense

29  Two plates carrying continental crust push together  Same density, neither one skins  Rocks crumple and fold to form mountains  Examples: European Alps, Himalaya


31  One plate of oceanic crust subducts (sinks) beneath another plate of oceanic crust  Older plate is colder and denser, and sinks below younger plate  Creates two features: ◦ Deep ocean trenches – deep canyons in ocean floor example: mariana trench ◦ Island arcs – chains of volcanic islands that form on the top plate parallel to trench. Example: Japanese islands


33  Ocean crust sinks under continental crust  Oceanic crust is colder and denser than continental crust  Features created: ◦ Deep ocean trenches – can cause underwater earthquakes ◦ Coastal Mountains – Examples: Cascade Mountains


35  Transform boundary: plates scrape past each other in opposite direction  Crust is neither created nor destroyed  Example: San Andreas Fault, San Francisco California



38  The plates lithosphere has been in motion for millions of years  By studying rock layers geologists can uncover the history of any region.  Plate tectonics gives scientists a way to study and predict geologic events such as earthquakes and volcanic activity

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