Earthquakes

Earth's outermost rigid rock area, the crust, is called the __lithosphere__. The lithosphere is split into 7 major plates.
 * African
 * Eurasian
 * Indian-Australian
 * Antarctic
 * Pacific
 * North American
 * South American

The 7 plates float on the __asthenosphere__, which is the uppermost part of the hot, liquid mantle.

__**Plate Boundaries**__ **__(pg 112 for pictures)__** Plates meet at a __plate boundary__. These are often sights of eqarthquakes and volcanoes. //3 Types of Plate Boundaries//
 * 1) **Divergent**- two plates are moving AWAY from each other. The result is new crust material formed at the diverging boundary.
 * 2) **Convergent**- two plates moving towards each other. The result is either an upward crunching of the plates, creating mountains, or one plate being pushed under the other. This is called __SUBDUCTION.__
 * 3) **Transform**- two plates sliding past each other.

Famous plate boundaries-
 * The San Andreas Fault between the North American Plate and the Pacific Plate (Transform Fault)
 * Parts of California rests on either side of this plate
 * Mt. St. Helens volcano in Washington is the result of leaking magma at this plate
 * The Himalayas were formed when the India-Australia plate collided with the Eurasian plate (Convergent Boundary)
 * The mid-Atlantic Ridge (Divergent boundary)

__**How Earthquakes Occur**__
 * As plates move, they release energy in vibrations and waves called __seismic waves__
 * The waves begin below ground at the __focus__ of the earthquake (the location of the origination of the waves)
 * The area above ground directly above the focus is called the __epicenter__. This location experiences the largest seismic movement.
 * Earthquakes can be very small or large. Over 1 million earthquakes occur each year.

__**Measuring Earthquakes**__ Seismic activity and waves are measured using a __seismograph__. An Earthquake can be quantified two ways
 * 1) The Richter Scale
 * The Richter Scale was invented by Charles Richter.
 * Each increase of "1" on the Richter scale indicates and increase of 30x magnification in power of the earthquake.
 * For example, an increase of 7 to 8 on the Richter Scale indicates an earthquake 30 times stronger than an earthquake ranked 7, and 900 times stronger than an earthquake ranked 6.
 * 1) The Moment Magnitude
 * Typically used by Seismologists to measure Earthquakes larger than 6.5
 * Measures the total energy released by the earthquake

__**Effects of Earthquakes**__
 * Magnitude 5 earthquakes usually damage property
 * Magnitude 2 earthquakes are generally too small to feel.
 * Approximately every 5 years a magnitude 8 earthquake occurs, causing massive property damage and death.
 * Earthquakes usually have an after-effect result of __landslides__ and __tsunamis__.

//Landslides// The seismic activity causes a break and release rocks, soil, and other debri, which slides swiftly down a mountainside.

//Tsunamis// An underwater earthquake, volcanic eruption, or landslide causes an intense wave through ocean water. This wave can travel through water at more than 750 km/ 450 miles per hour. Tsunamis may start at about 1 m high in ocean water but reach 30 m high (a 10 story building) as they approach the shallower waters near a shoreline. __Economic and Environmental Effects of Tsunamis__
 * Coastal degradation from the impact and current of the wave
 * displaced animals left ashore after the wave leaves
 * Destruction of coastal infrastructure
 * pollution of local coastal area by saltwater
 * Oil and gasoline from overturned vehicles causes water pollution
 * Damage of reefs and offshore coastal environments


 * __Famous Earthquakes/Tsunamis/Fault Areas__**

1. **Pakistan** October 8, 2005
 * killed 75,000 people
 * Eurasian and Indian-Australian plate collision

2. **Peru** 1970
 * resulting landslide killed 17,000 people, buried an entire town

3. **South Asian (Indonesia) Tsunami** December 26, 2004
 * Indian Ocean earthquake, magnitude 9.4
 * largest earthquake since Alaskan earthquake in 1964
 * more than 240,000 people died
 * tsunami affected South Asia and east coast of Africa

4. **San Andreas Fault/California Activity (esp 1906 earthquake)**
 * One of the most geologically active areas of the world
 * Pacific plate is moving northward at 3.5 cm/year
 * 1906 8.3 magnitude Earthquake destroyed most of San Fransisco (most damage due to fire caused by ruptured gas lines after the quake)
 * 1989 6.9 magnitude earthquake in Loma Prieta (90 mi south of San Fran) killed 67 people and caused $6 billion in damage

5. **Kobe, Japan** 1995
 * occurred at smaller faults crisscrossing major plate
 * was difficult to predict because it is a smaller fault and only experiences serious magnitude quakes every 1000-5000 years.