Wegner’s Theory Of Continental Drift :

1. Wegner’s Theory Of Continental Drift : BY : Shelby Babb

2. CONTINENTAL DRIFT : • is the movement of the earths continents relative to each other by appearing to drift across the ocean bed . • Evidence : Evidence for the movement of continents on tectonic plates is now extensive similar plant and animal fossils are found around different continent shores and may once have been joined together • Problems with theory : one problem was that plausible driving force was missing and it didn’t help that wegner wasn’t a geologist.

3. SUPERCONTINENT THEORY : • Supercontinent theory : that continents will move farther apart as years pass . • Supercontinent Cycle : is the quasi – periodic aggregation and dispersal of earths continental crust • Panthalassa means all seas ; pangaea was a supercontient that existed in during the late paleozoic and mesozoic eras • Accretion : (astrophysics) which material is added to a tectonic plate or landmasses . • Rifting : is a linear zone where the Earths Crust and lithosphere is are being pulled apart . • How plate movement alter climates and evolution ? The climates adapt as the continents move . For example Antarctica was once close to the equator

4. Theory Of Plate Tectonics • Lithosphere : is the rigid outermost shell of a rocky planet . • Asthenosphere : is the highly viscous mechanically weak and deforming region of the upper mantle of the earth . • How plates move ;because of high temperatures and immense pressures . • Three types of plate boundaries; Divergent boundaries , Convergent boundaries , Transform boundaries . • Isostatsy : term used in geology to refer to the state of gravitational equilibrium between the earths lithosphere and asthenosphere . • Isotactic Adjustments : is the rise of land masses that were depressed by huge pieces of ice sheets . • Stress : The state of stress in the lithosphere provides strong constraints on the forces acting on the plates .

5. Divergent Boundary : Lands forms; ( mid - ocean ridges ) where new oceanic crust if formed formed through volcanic activity than gradually moves away from the ridge . Red sea is an example of landforms the process starts with heating at the base of the continental crust which causes it becomes more plastic and less dense.

6. Paleomagnetism : • Magnetic reversals ; also known as flip , is the process which the north pole is transformed into the south pole and the south becomes the north , the Earth's magnetic field has undergone numerous reversals of polarity. • Magnetic Symmetry ; At the mid ocean ridge the oceanic plates are separating taking half of the lava on either side over time the magnetic poles move around.

7. Normal Faults : • Related landforms ; were plates generally occur in places where the lithosphere is being stretched . They also can be found in deltas at the rear edges of huge gravitation . • Examples ; very low-angle normal faults , active normal faults can be shown to dip at angles steeper than 50 degree

8. Convergent Boundary : • Subduction zones ; Continental & oceanic crust :Continental crust is the layer of igneous , sedimentary , and metamorphic rock which forms continents . & oceanic crust is the part of earths lithosphere that surfaces in the oceans basins . Landforms produced : stretches the landforms above the surrounding land in an limited area In a form of a peak . Examples : folded mountains , fault block mountains , dome mountains , and plateau mountains Oceanic & oceanic crust : the pacific ring of fire is also a result of convergent boundaries in the Ocean

9. what are common locations of volcanos ? • Volcano : is an opening in a planets surface which allows hot magma volcanic ash and gases to escape from the magma chamber below the surface. • The most common perception of a volcano is of a conical mountain • Major zones : being part of the Ring of Fire ; the ring of fire is apart with the edges of one of the world's main tectonic plates, contains over 450 volcanoes has approximately 75 percent of the worlds active volcanoes.

10. Pyroclastic Material : • Viscosity : is a measure of the resistance of a fluid which is being deformed by either shear stress or tensile stress. • How does magma content produce explosive eruptions : gas gives magma the explosive character the gas forms a separate vapor phases when pressure is decreased .

11. Types of volcanoes : • Shield volcanoes : is a type of volcano built of entirely of fluid lava flows . • Examples : The Hawaiian shield volcanoes are the most famous examples • Mauna Kea ; Mauna Loa ; Hualalai ; Kohala are the 4 volcanoes that happen in hawaii

12. Cinder Cones Volcanoes : • Are found on the flanks of shield volcanoes . Examples : • amples are SP Crater located in the San range Francisco Mountain range .

13. Composite volcanoes : • form when runny lava escapes through a fissure and flows down a long way . • Examples : Andesite magma (the most common but not the only magma type tends to form composite cones.

14. Caldera : • are ones where the diameter of the circular to oval crater exceeds 1 mile long . • Examples :Crater Lake in Oregon was created when a volcano detonated around 10,000 years ago. The volcano Kilauea of Hawaii has a magma chamber by large lava flows

15. Video of a volcano erupting ; • Picture of a volcano Erupting : video http://video.nationalgeographic.com/video/environment/environment-natural-disasters/volcanoes/volcano-lava/

16. Collision zones • Continental and continental crust : is the layer of igneous , sedimentary , metamorphic rocks . • Compression & uplift : compression the result of the subjection of a material to compressive stress ; uplift :as one plate goes down another goes up . • Landforms produced ; folded mountains worlds largest mountain range • Plateaus not formed by internal activity ; Dome is amount of melted rock (magma) pushing its way up under the earth

17. Transform Boundary : • Reverse Faults : they result in occur in faults undergoing compression • Strike – Slip Faults : A dislocation caused by a slipping of rock masses along a plane of facture also the dislocates structure resulting from such slipping. • Tension : is the pulling force exerted by a string, cable, chain, or similar solid object on another • Sheer Stress : is the component of stress with a cross section • Fault Block Mountains ; Sierra Nevada mountains • Grabens : depressed block of land bordered by parallel faults

18. Earthquakes : • Elastic Rebound : a theory of earthquakes that envisages gradual deformation of the fault zone without fault slippage until friction is overcome , when the fault suddenly slips to produce the earthquake . • Seismology ; Seismograph : are instruments that measure motions of the ground including those of seismic waves generated by earthquakes volcanic eruptions, and other seismic sources. • Focus :an earthquakes underground point of origin or hypocenter • Epicenter : is the point on the Earth's surface that is directly above the hypocenter or can earthquake or underground explosion had started

19. Seismic Waves : • Body waves : travel through the interior of the Earth . They create ray paths refracted by the varying density and of the Earth's interior. The density and modulus vary according to temperature, composition, and phase.

20. P Waves : • Primary waves are compressional waves that are longitudinal in nature. P waves are pressure waves that travel faster than other waves through the earth to arrive at seismograph stations first hence the name "Primary". These waves can travel through any type of material, including fluids, and can travel at nearly twice the speed of S waves.

21. S Waves : • Secondary waves (S-waves) are shear waves that are transverse in nature. These waves arrive at seismograph stations after the faster moving P waves during an earthquake and displace the ground perpendicular to the direction of propagation.

22. Surfaces waves : • Surface waves also known as ( L waves ) are analogous to water waves and travel along the Earth's surface. They travel slower than body waves. They are called surface waves because they diminish as they get further from the surface

23. Earthquakes Not resulting from Movement : • Almost all earthquakes occur at the edges of the crustal plates. The constant bumping, grinding, and lateral movement along crustal boundaries can create sudden movements that result in earthquakes. • convergent boundaries: subduction and collision. subduction boundary is marked by the oceanic crust of one plate that is being pushed downward beneath the continental or oceanic crust of another plate

24. Mercalli Scale : • a seismic scale used for measuring the intensity of an earthquake • The lower degrees generally deal with the fact in which the earthquake is felt by people. The higher numbers of the scale are based on observed structural damage. • Modified Mercalli Intensity example : • Under 2.0 I • 2.0 – 2.9 I – II • 3.0 – 3.9 II – IV • 4.0 – 4.9 IV – VI • 5.0 – 5.9 VI – VIII • 6.0 – 6.9 VII – X • 7.0 – 9.9 VIII or higher • 10.0 or higher X or higher

25. Magnitude : • the relative size of an object • Intensity : is a measure of the energy flux • For example : take the energy density the energy per unit volume and times it by the velocity at which the energy is moving.

26. Tsunami : • Are giant waves cause by an earthquake . • Examples : The volcanic eruption on Santorini Greece A tsunami is assumed to be the factor that caused the most damage • Persian attackers who tried to exploit an unusual retreat of the water were suddenly surprised by a great flood-tide .

27. Pictures of tsunamis :

28. Earthquake : • http://sfist.com/2009/04/13/live_footage_from_1989_earthquake.php