Dynamic+Crust

Dynamic Crust

 Theory of Continental Drift: Alfred Wegener 1915


 * I Pangea- A large landmass containing all of the continents, which eventually broke into two landmasses.
 * A) Laurasia- n. America, Europe, Asia
 * B)Gondwanaland- Africa, S. America, Antarctica, Australia, India

Evidence:  Structure of Earth:  Plate tectonics-  Earthquakes-  Depth of Earthquakes:  Earthquake Waves:  Locating an Earthquake: 
 * Continents seem to fit together
 * Fossils of individual species can be found on many different continents, which are not close together, (EX. Lystrosaurus was located in Antarctica, sounth America, Africa and India)
 * Deposits of certain rock and mineral types correlate among continents
 * Appalachian Mountains found in northeast of the United States are similar in age and structure and mountains in Greenland and Scandinavia.
 * <span style="font-family: Verdana,Geneva,sans-serif;">Pressure and temperature increases as you move toward the center of the earth
 * <span style="font-family: Verdana,Geneva,sans-serif;">Crust-The outer most layer of the earth
 * <span style="font-family: Verdana,Geneva,sans-serif;">A) Continental Crust- Composed mainly of Granite, Low in density
 * <span style="font-family: Verdana,Geneva,sans-serif;">B) Oceanic Crust- Composed mainlhy of basalt, High in Density
 * <span style="font-family: Verdana,Geneva,sans-serif;">Lithosphere: Crust and uppermost solid part of the mantale
 * <span style="font-family: Verdana,Geneva,sans-serif;">Asthenosphere- Underlies the lithosphere, compsed of partially molten rock
 * <span style="font-family: Verdana,Geneva,sans-serif;">Asthenosphere- Underlies the lithosphere composed of partially motlten rock
 * <span style="font-family: Verdana,Geneva,sans-serif;">Moho- The boundry between the crust and the mantle.
 * <span style="font-family: Verdana,Geneva,sans-serif;">Mantle- The layer of molton rock extending from the crust downward 2850 KM
 * <span style="font-family: Verdana,Geneva,sans-serif;">Outer Core- Between mantle and inner core, composed of iron and nickel
 * <span style="font-family: Verdana,Geneva,sans-serif;">Inner Core- Solid iron and nickel located at the center of the earth
 * <span style="font-family: Verdana,Geneva,sans-serif;">Plate tectonics is the study of the formation and movement if plates
 * <span style="font-family: Verdana,Geneva,sans-serif;">Plates are composed of lithosperev(continental= thick oceanic= thin) 12 major and several minor plates.
 * <span style="font-family: Verdana,Geneva,sans-serif;">An earthquake is a shaking of earth’s crust caused by the realese of energy.
 * <span style="font-family: Verdana,Geneva,sans-serif;">Reasons why they occure:
 * <span style="font-family: Verdana,Geneva,sans-serif;">Eruption of a Volcano
 * <span style="font-family: Verdana,Geneva,sans-serif;">The Collapse Of a Cavern
 * <span style="font-family: Verdana,Geneva,sans-serif;">The impact of a meteor
 * <span style="font-family: Verdana,Geneva,sans-serif;">Sudden movement along a plate boundary caused by the release of stress.
 * <span style="font-family: Verdana,Geneva,sans-serif;">Focus : The point on a fault plane at which the first movement occurs
 * <span style="font-family: Verdana,Geneva,sans-serif;">Epicenter: The point on earths surface directly about the focus
 * <span style="font-family: Verdana,Geneva,sans-serif;">Three Basic kinds of waves:
 * <span style="font-family: Verdana,Geneva,sans-serif;">P-Waves(Primary)- Back and Forth wave motion; can travel through any material; fastest
 * <span style="font-family: Verdana,Geneva,sans-serif;">S- Waves (Second)- Side to side wave motion; can travel through solids but not through liquids or gases.
 * <span style="font-family: Verdana,Geneva,sans-serif;">L-Waves (surface waves) form when P and S waves reach the surface which move slowly like ripples on a pond; slowest
 * <span style="font-family: Verdana,Geneva,sans-serif;">Seismograph: The intrument that detects and records earthquake waves
 * <span style="font-family: Verdana,Geneva,sans-serif;">Seismogram: The sheet which displays the zig-zag trace of earthquake waves
 * <span style="font-family: Verdana,Geneva,sans-serif;">P waves always arrive before S waves
 * <span style="font-family: Verdana,Geneva,sans-serif;">P and S waves arrival time difference can then be used to derermine the distance from the recording station to the epicenter

Locating and Epicenter:

<span style="font-family: Verdana,Geneva,sans-serif;"> Shadow Zone
 * <span style="font-family: Verdana,Geneva,sans-serif;">Triangulation:
 * <span style="font-family: Verdana,Geneva,sans-serif;">We then use the epicenter distancefrom at least 3 recording stationw to locte the empicent4er
 * <span style="font-family: Verdana,Geneva,sans-serif;">You need to next measure the distance to scale and drawing a circlefrom each station, Once threee citcles are drawn they will internsect at oine common point. This location is the epicenter.

<span style="font-family: Verdana,Geneva,sans-serif;"> Plate Tectonics · Plate tectonics is the study of the formation and movement of plates · Plates are composed of lithosphere (continental = thick. oceanic = thin 12 major and several minor plates
 * <span style="font-family: Verdana,Geneva,sans-serif;"> The shadow zone is a wide belt aound the earth the side opposite ttghe earthquake. See nethier P or S was=v=in the earth
 * <span style="font-family: Verdana,Geneva,sans-serif;"> The cause of the shadow zone is the earths outer cors, s waves can not travel trough the liwuid outer cors. While p waves are refracted(bent) in a smooth BC back to the surface

<span style="font-family: Verdana,Geneva,sans-serif; font-size: 14px; line-height: normal;"> Plates move because of convection cells in the asthenosphere <span style="font-family: Verdana,Geneva,sans-serif;"> Convectioncell- A circulatory motion in a liquid or gas transferring heat energy that results from differences in density within the fluid

Divergent Plate Boundary <span style="font-family: Verdana,Geneva,sans-serif;"> http://geology.com/nsta/divergent-boundary-oceanic.gif
 * <span style="font-family: Verdana,Geneva,sans-serif;"> Place where two plates are moving apart from each other
 * <span style="font-family: Verdana,Geneva,sans-serif;">Mid - Atlantic Ridge- sea floor spreading at the mid ocean ridges recorded by the reversal of the magnetic poles in mineral grains

Paleomagnetism- the study of magnetism in ancient rocks <span style="font-family: Verdana,Geneva,sans-serif;"> Convergent Plate Boundary <span style="font-family: Verdana,Geneva,sans-serif;"> http://geology.com/nsta/convergent-boundary-oceanic-continental.gif
 * <span style="font-family: Verdana,Geneva,sans-serif;"> Polar Wandering- as metallic mineral grains align themselves with their magnetic poles rock records show that the grains reverse the direction in which they point
 * <span style="font-family: Verdana,Geneva,sans-serif;">When two plates move towards each other
 * <span style="font-family: Verdana,Geneva,sans-serif;">Collision- When two plates carrying continents collide they push up usually causeing mountains. (EX. HIMALAYAS)
 * <span style="font-family: Verdana,Geneva,sans-serif;">Subduction - When both plates do not contain continents, one of the plates is forced to sink under the other one.

Transform Plate Boundry <span style="font-family: Verdana,Geneva,sans-serif;"> http://geology.com/nsta/transform-boundary.gif
 * <span style="font-family: Verdana,Geneva,sans-serif;"> When plates slide past one another usually causeing a build of pressure which is released in the form of an earthquake
 * <span style="font-family: Verdana,Geneva,sans-serif;">San Andreas Fault- Many earthquakes are common along the fault where the north american plate is sliding past the pacific plate.

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The Plate Which Subdues Is Composed Of A More Dense Material <span style="font-family: Verdana,Geneva,sans-serif;"> The Ring of Fire: <span style="font-family: Verdana,Geneva,sans-serif;"> Volcanism <span style="font-family: Verdana,Geneva,sans-serif;"> Magma contains dissolved gases that are given off as the magme erupts. The most important of these gases are water vapor, carbon dioxide and sulfur. Magmas containing large amounts of dissolved gases tend to produce more explosive
 * <span style="font-family: Verdana,Geneva,sans-serif;">Ocean- Continent - The ocean floor is more dense so it subdues to the continental causeing offshore trenches, mountains or volcanoes (EX. Western Coast of S. America)
 * <span style="font-family: Verdana,Geneva,sans-serif;">Ocean- Ocean- One plate will subdue to the other one usually causeing a deep trench (EX. Mariana's Trench)
 * <span style="font-family: Verdana,Geneva,sans-serif;">Earthquakes and Volcanoes along the Pacific Ocean.
 * <span style="font-family: Verdana,Geneva,sans-serif;">Magma-Molten Rock Underground
 * <span style="font-family: Verdana,Geneva,sans-serif;">Felsic- Magmas with relatively high silica are thick, light colored and slow moving
 * <span style="font-family: Verdana,Geneva,sans-serif;">Mafic- Relatively low silica content, thinner, darker and flow more easily.

<span style="font-family: Verdana,Geneva,sans-serif;"> Lava Fragments- Tephra- Solid fragments of lave produced from explosive eruptions
 * **<span style="font-family: Verdana,Geneva,sans-serif;">LAVA- **<span style="font-family: Verdana,Geneva,sans-serif;">Molten Rock that has reached the surface
 * <span style="font-family: Verdana,Geneva,sans-serif;">Felsic Lava- Thick and stiff called **<span style="font-family: Verdana,Geneva,sans-serif;">AA Lava **<span style="font-family: Verdana,Geneva,sans-serif;">. Produce explosive eruptions
 * <span style="font-family: Verdana,Geneva,sans-serif;">Mafic Lava- Thin and fluid called **<span style="font-family: Verdana,Geneva,sans-serif;"> Pagoehoe lava. **<span style="font-family: Verdana,Geneva,sans-serif;"> Lava pours out smoothly (Les Explosive)

Kinds of Eruptions:
 * Rift Eruptions- Occur at long, narrow fractures in the crust such as mid-ocean spreading centers
 * When Lava flows out smoothly and fluidly it forms a volcanic mountain with a broad base and gently sloping side called a shield cone.
 * Subduction Boundary Eruptions- are the result of thick magma that forms at subduction boundaries. These eruptions are more explosive due to the large amount of gases in the magma.
 * Forms a cinder cone with very steep sides.

Hot Spots: (check E.R.S.T)
 * Hot spots are areas of volcanic activity in the middle of lithospheric plates.
 * Similar to rigt eruptions. Smooth flowing lava and shield cones.
 * **THE HOT SPOT STAYS IN TH SAME LOCATION AS THE LITHOSPHERIC PLATE ABOVE IT MOVES**