Science

theory of continental drift (alfred wegener 1915)

1. Pangea- A large landmass containing all the continents which eventually broke into two landmasses

a) laurasia- N. America, Europe, Asia B) Gondwanaland- africa, s. America, Antarctica, Australia, india


 * __Evidence__**

Continents seems 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, S. America, India, Africa ) Deposits of certain rock and mineral types correlate among contents Appalachian Mts. found in northeast of U.S. are similar in age and structure as mts. in greenland and scandinavia.


 * __Structure of the earth__**

Pressure and temperature increase as you move toward the center of the earth Crust- The outer most layer of the earth A) continental crust- composed mainly of granite, low in density B) Oceanic crust- composed mainly basalt, high in density Lithosphere- Crust and uppermost solid part of the mantle Asthenosphere- underlies the lithosphere, composed of partially molten rock Moho- the boundary between the crust and the mantle Mantle- The layer of molten rock extending from the crust downward 2850 KM Outer core- Between mantle and inner core composed of iron and nickel Inner Core- Solid iron and nickel located at the center of the earth


 * __Plate tectonics__**

Plate tectonics is the study of the formation and movement on plates Plates are composed of lithosphere ( continental= thick, oceanic= thin) 12 major and several minor plates

an earthquake is shaking of earth's crust caused by the release of energy. Reasons why they occur- Eruption of a volcano the collapse of a cavern the impact of a meteor sudden movement along a plate boundary caused by the release of stress
 * __Earthquakes__

**__Depth of earthquakes__ Epicenter- the point on earth's surface directly above the focus**
 * Focus- the point on a fault plane at which the first movement occurs

__Earthquake waves__

P-waves(primary)- back and forth wave motion; can travel through and material;fastest S-waves(Secondary)- side to side wave motion; Can travel through solids but not through liquid or gases L-waves(surface)- From when P and S waves reach the surface which move slowly like ripples on a pound; slowest**
 * three basic kinds of waves

__Locating an earthquake__ Seismogram- the sheet which displays the zig-zag trace of earthquake waves **P-Waves always arrive before S-Waves
 * seismograph- the instrument that detects and records earthquake waves
 * P and s wave arrival time difference can then be used to determine the distance from the recording station to the epicenter.**

__**Locating an epicenter**__

Triangulation- we then use the epicenter distance's from at least 3 recoding stations to locate the epicenter You need to next measure the distance to the scale and drawing a circle form each station. Once 3 circles are drawn they will intersect at one common point. This location is the epicenter.

__**Shadow Zone**__

The shadow zone is a wide belt around earth on one side opposite the focus of the earthquake. Seismic stations receive neither P Nor S waves The Cause of the shadow zone is that earth's out core S-Waves can not travel through the liquid core. while P-Waves are refracted (bent) in a smooth BC back to the surface

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