catalyst n.
Skip this Video
Loading SlideShow in 5 Seconds..
Catalyst PowerPoint Presentation


337 Vues Download Presentation
Télécharger la présentation


- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Catalyst • List 6 Pieces of Evidence for Continental Drift. • List the Layers of the Earth. Which layers do you think are more/less dense?

  2. Continental Drift • Developed by Alfred Wegner • Belief that Earth’s continents were joined as a single landmass (Pangaea) and began to break apart 200 million years ago

  3. Evidence for Continental Drift 1. Similar rock formations on opposite sides of the Atlantic Ocean. 2. Similar fossils of several different animals and plants that once lived on land found on widely separated continents. Mesosaurus, a small reptile, fossils are found in Brazil and S. Africa but are not found anywhere else on Earth.

  4. 3. Similarities in shapes of the coastlines of continents. (Western coast of Africa and eastern coast of S. America) 4. Coal deposits found in Antarctica. Coal forms from dead swamp plants in areas of wet, spongy land often covered by water. Region had to have once been a temperate, rainy climate.

  5. 5. Glacial deposits found in Africa, India, Australia, and S. America. The presence of these 290 million year old deposits indicates that these areas had once been covered by thick ice caps. 6. Earthquake and volcanic activity do not occur randomly throughout the world. Occur in belts and mark the location of plate boundaries.

  6. The layers of Earth • Crust • Oceanic – more dense • Continental – older, thicker, and less dense • Mantle • Molten material • Crusts float on mantle because they are less dense • Continental crust floats higher than oceanic crust • Core • Inner core – solid • Outer core – molten • More dense than mantle

  7. The rocky material of the mantle moves in very slow convection currents. This movement is related to density and temperature differences in the mantle. Hot material is less dense and rises. Cold material is denser and sinks. 28.1 Convection inside Earth

  8. The theory of plate tectonics explains the movement of continents and other geological events like earthquakes and volcanoes. The term tectonics means construction or building. The theory of plate tectonics, stated in 1965, refers to the movement of giant pieces of solid rock on Earth’s surface called tectonic plates. 28.2 Plate Tectonics

  9. Plate Tectonics • Movement of one plate causes the pulling or pushing of other plates • At plate boundaries, crust may be created, destroyed, crumpled into mountains, or none of these. • The tectonic plates that cover Earth’s surface are pieces of the lithosphere that fit together and float on the asthenosphere (a part of the mantle).

  10. Can you identify which of the plates are only made of oceanic crust?

  11. There are three main kinds of plate boundaries: divergent convergent transform 28.2 Describing Plate Boundaries

  12. Diverging plates move apart and new crust forms. 28.2 Divergent Plate Boundaries

  13. Divergent boundaries are sites of earthquakes and volcanic activity. Mid-ocean ridges and associated sea-floor spreading occur at divergent plate boundaries. In effect, a mid-ocean ridge is like a very long volcano. 28.2 Divergent Plate Boundaries

  14. Convergent plate boundaries occur where two plates approach each other. One result of two plates converging is subduction. A deep oceanic trench marks the boundary between a subducting and an overriding plate at a convergent boundary. 28.2 Convergent Plate Boundaries

  15. The movement of tectonic plates is related to the distribution of heat by convection currents in the mantle. 28.2 Movement of Plates

  16. The Mariana Trench (or Marianas Trench) is the deepest part of the world's oceans, and the deepest location on the surface of the Earth's crust. It has a maximum depth of about 10,911 meters[1] (35,798 feet; 6.78 miles), and is located in the western North Pacific Ocean, to the east and south of the Mariana Islands, near Guam.

  17. The Cascade Range is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California.

  18. mid-ocean ridge topography

  19. 28.2 Magnetic Patterns • Over geologic time, the magnetic polarity of Earth has switched. • Scientists believe the poles switch because of a magnetic interaction between the planet’s inner and outer core. • In the 1950s and 1960s, scientists discovered that the rocks of the sea floor have a very interesting magnetic pattern.

  20. 28.2 Magnetic Patterns • Stripes of rock with a north-south orientation (normal) alternate with stripes of rock with a south-north orientation (reversed). • The blue and white stripes you see in the figure are an interpretation of a magnetic profile.


  22. What causes convection currents? • In the atmosphere? • In the oceans (hydrosphere)? • In the mantle (lithosphere and asthenosphere)?

  23. What is the internal source of Earth’s energy? • The Core! • But how? • Heat left from Earth’s formation • Heat generated by nuclear reactions occurring in the core (fission reactions)

  24. Worldwide Earthquakes

  25. Most volcanic activity is found at the edges of tectonic plates, namely at divergent and convergent plate boundaries, but does not occur at transform plate boundaries. 29.1 Volcanoes

  26. Volcanoes also form when an oceanic plate slides under another oceanic plate. 29.1 Volcanoes

  27. Hot Spots • Hot spots are fixed places within the mantle or oceanic lithosphere, where rocks melt to generate magma.  When a hot spot is situated in the oceanic lithosphere a class of volcanoes known as shield volcanoes is built.  These are constructed on the deep ocean floor and may be build high enough to rise above sea level as volcanic islands.  The Hawaiian hot spot, for example, has been active at least 70 million years, producing a volcanic chain (of shield volcanoes) that extends 3,750 miles (6000 km) across the northwest Pacific Ocean.