Presentation on theme: "The Structure of the Earth and Plate Tectonics mini version."— Presentation transcript:
The Structure of the Earth and Plate Tectonics mini version
The Crust This is where we live! The Earth’s crust is made of: Continental Crust - thick (10-70km) - buoyant (less dense than oceanic crust) - mostly old Oceanic Crust - thin (~7 km) - dense (sinks under continental crust) - young
Plate Tectonics The Earth’s crust is divided into 12 major plates which are moved in various directions. This plate motion causes them to collide, pull apart, or scrape against each other. Each type of interaction causes a characteristic set of Earth structures or “tectonic” features. The word, tectonic, refers to the deformation of the crust as a consequence of plate interaction.
Alfred L. Wegener Geologist Alfred Wegener noticed similar rocks & fossil remains were found on continents which seemed to fit togetherGeologist Alfred Wegener noticed similar rocks & fossil remains were found on continents which seemed to fit together He called this “super” continent called PangaeaHe called this “super” continent called Pangaea In 1912 Wegener published the first version & died defending his theoryIn 1912 Wegener published the first version & died defending his theory
PANGAEA - the large landmass that included all of Earth’s present day continents
Support for Continental Drift 1. SHAPE OF THE CONTINENTS Continents fit together like puzzle pieces
Mesosaurus was incapable of swimming across a large ocean. 2. FOSSIL EVIDENCE SAME FOSSILS: DIFFERENT CONTINENTS Support for Continental Drift
3. ROCK EVIDENCE – Mountain ranges Support for Continental Drift SAME ROCK: DIFFERENT RANGE Existing mountain ranges separated by vast oceans contain rocks of identical mineral content. A prime example are the Appalachian Mountains in the eastern U.S and the Caledonian Mountains in the British Isles. SAME ROCK: DIFFERENT RANGE Existing mountain ranges separated by vast oceans contain rocks of identical mineral content. A prime example are the Appalachian Mountains in the eastern U.S and the Caledonian Mountains in the British Isles.
SAME SCARS: DIFFERENT CONTINENTS Support for Continental Drift 4. GLACIAL SCARS
5. LOCATION OF COAL DEPOSITS Coal deposits have been found in temperate and polar regions; however, coal is formed in tropical regions. Support for Continental Drift
Plate Movement “Plates” of lithosphere are moved around by the underlying hot mantle convection cells
Divergent Convergent Transform Three types of plate boundary
Iceland has a divergent plate boundary running through its middle Iceland: An example of continental rifting
There are three styles of convergent plate boundaries Continent-continent collision Continent-oceanic crust collision Ocean-ocean collision Convergent Boundaries
Forms mountains, e.g. European Alps, Himalayas Continent-Continent Collision
Called SUBDUCTION Continent-Oceanic Crust Collision
When two oceanic plates collide, one runs over the other which causes it to sink into the mantle forming a subduction zone. The subducting plate is bent downward to form a very deep depression in the ocean floor called a trench. The worlds deepest parts of the ocean are found along trenches. E.g. The Mariana Trench is 11 km deep! Ocean-Ocean Plate Collision
Where plates slide past each other Transform Boundaries Above: View of the San Andreas transform fault
Volcanism is mostly focused at plate margins Pacific Ring of Fire
Hot mantle plumes breaching the surface in the middle of a tectonic plate What are Hotspot Volcanoes? Photo: Tom Pfeiffer / The Hawaiian island chain are examples of hotspot volcanoes.
Where do earthquakes form? Figure showing the tectonic setting of earthquakes
What is an earthquake? They are caused by the release of energy They cause the ground to shake Reasons: Plates Moving Faults (cracks in Earth’s surface) Caverns collapsing Meteor Impacts Volcanic Eruptions
The San Andreas is a Strike Slip (Transform) Fault One piece of Earth slides past another
Terms used to describe an earthquake Focus vs. Epicenter Focus: area beneath Earth’s surface where rock that was under stress begins to move or break. Epicenter: Point on surface directly above the focus.
How are earthquakes detected? Earthquakes are detected by seismographs Seismographs record the information on a seismogram
How is the strength of the earthquake determined? Intensity The effect of the Earthquake on the area Measured by the Mercalli Scale (shaking) Magnitude The actual energy released by the Earthquake Measured by the Richter Scale (I-XII)