Basic+Information+about+Earthquakes+and+Japan

The earth is made up of four layers **crust:** hard and rigid; it's the earths outermost layer and the thinnest **mantle:** its made of hot semisolid rock and divided into two parts the upper and lower **outer core:** the onlyliquid layer of earth and is mostly made of iron and nickel. **inner core:** the hottest layer a mostly solid layer made of iron and nickel

__**lithosphere**__: contains the crust and the upper part of the mantle and is divided into several constantly moving plates of solid rock that hold the continents and oceans. __**asthenosphere**:__ the plates(lithosphere) move on this hot semi liquid in the upper mantle directly above the lithosphere

Pangaea is a super continent developed by Alfred Wagner that broke apart around 200 million years ago due to continental drift due to plate tectonics

"the plate tectonics theory states that the earths outer layer the lithosphere is broken into several large slabs called slabs called plates. These plates which hold the continents and oceans are constantly moving. The movement of the plates explain how and why earthquakes, volcanoes, and other geological events occur."

**continental crust**: under the continents **oceanic crust:** under the oceans denser and less thick
 * __why plate tectonics move:__** The lithosphere is made up of slabs called plates they are in constant motion because inside the asthenosphere there is a semi solid layer where convection currents are moving the magma up and down and because the plates float on the asthenosphere they move along with it.

the place where two plates meet is called a boundary //convergent//: boundary occurs where two plates are pushing towards to each other //divergent//: boundary where two plates are moving apart from each other //transform:// boundary occurs where two plates slide past each other

CONVERGENT BOUNDARY at a convergent boundary where a oceanic plate and a continental plate meet the oceanic crust usually subducted beneath the continental creating deep trenches as the crust in pushed farther into the ground the base melts creating magma.

"The magma formed at a subduction zone rises up toward the earth's surface and builds up in magma chambers, where it feeds and creates **volcanoes** on the overriding plate. When this magma finds its way to the surface through a vent in the crust, the volcano erupts, expelling lava and ash. An example of this is the band of active volcanoes that encircle the Pacific Ocean, often referred to as the Ring of Fire."

when two oceanic plates collide one is pushed under the other creating a chain of volcanic islands known as island arches. because when two plates collide they can create large earthquakes which in turn can create large tsunamis. when two continental plates collide the plates are not subducted they build up leading the creation of mountains and mountain ranges DIVERGENT BOUNDARY when oceanic plates spread apart magma comes to the surface making a raised area called a mid-oceanic ridge it also spreads outward forming new ocean floor and new oceanic crust. when two continental plates diverge they form rifts and rivers and streams begin to flow through it making it very thin which could lead to it breaking off and creating a new tectonic plate and at that point ocean water will come rushing in forming a new ocean in the rift zone at a divergent boundary magma can come to the surface and create volcanoes also known as rift volcanoes. TRANSFORM BOUNDARIES

when two plates rub past each other it results in a line called a fault sometimes the plates become lodged building up pressure and when released they make earthquakes a transform boundary has been given a name as a strike-slip fault [] **epicenter:** the point on earth surface just above the earthquakes focus __Japans earthquake:__ Japan is either on or close to the boundary of four tectonic plates: the Pacific, North American, Eurasian which are primary plates, and Philippines Sea plate, which is one of the secondary plates. The earthquake hit the eastern coast of Japan. The sudden movement of the Pacific tectonic plate under the North American plate caused a massive earthquake and a tsunami. The pacific plate because it is denser was pushed or subducted underneath the North American Plate releasing large amounts of energy. The upward thrusting plate displaces water creating a ripple affect tsunami that hit shore in about 15 minutes. The waves started from the epicenter starting off with low heights and long wave lengths then it reached 500 miles an hour and as it reached shallower water the height of the waves built into in some places 20ft waves that crashed against the shore. The epicenter of the earthquake was off the coast of Sendai and north of Tokyo. The earthquake created a 15 mile trench and pushed eastern Japan 13ft closer to North American and shifted the earths axis 6.5 inches

__japans earthquake preparedness:__ Earthquake drills are mandatory is Japan and important businesses carry earthquake kits that include flashlights and first aid. However its there technology."There are three main types of "earthquake proof" building structures, all used in Japan over the past decade. **heavy concrete weight on the top of a building that, activated by computer-controlled dampers, is shifted across the roof to counteract the force of the earthquake;** The second employs**shock absorbers, normally a sandwich rubber composition that acts as a form of suspension; this is suitable for buildings up to 15 stories.** "**has steel braces providing stiffness for moderate earthquake motions,** absorbing seismic energy and acting as a fuse which prevents the braces from bucklingThey are hydraulic cylinders that elongate and contract as the building sways, sapping the motion of energy.." built concrete seawalls in many communities, some as high as 40 feet, which amounted to its first line of defense against the water. In some coastal towns, in the event of an earthquake, networks of sensors are set up to set off alarms in individual residences and automatically shut down floodgates to prevent waves from surging upriver."(Glanz ) Glanz, James. "Japan’s Strict Building Codes Saved Lives." //New York Times// 11 March 2011, Print.
 * Japans earthquake technology || advantages || disadvantages ||
 * heavy concrete weight at the top of the building activated by a computer || it counteracts the force of the earthquake to keep the building from collapsing || it is activated by a computer ||
 * 40ft seawalls || the countries first defense against tsunami waves || critics complained they were and eye sore and bad for the environment. They also in many places did not protect against Friday's tsunami waves. ||
 * advanced devices called base isolation pads and energy dissipation units || used to minimize the shaking due to the earthquake || Japan has spent billions of dollars installing and building this technology ||