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What is a Tsunami?
Difference between tsunami and storm waves
A wave is not "water moving"; it is energy passing through water, agitating the water molecules and then leaving the same molecules behind (except when a wave breaks on a coast when water is indeed "moved" if only briefly onto land). The energy of waves in the drawings below is symbolised by a circle or an oval.
Wind-created waves do not reach deep below the surface although in severe storms they can reach heights of 7 m or more ( "freak waves" can go much higher, they are very rare and their origin is not well understood). A few meters below a surface whipped by a raging storm, all is quiet.
Tsunami waves are quite different. On seas with a depth of 4000 m or more, the tsunami's height on the sea surface may be less than 0.8 m and hardly noticeable. Indeed, almost all of the tsunami's energy is below the sea surface and sailors may not even notice a major tsunami wave passing under their ship.
in shallow seas and very close to the epicentre, tsunami waves have been known to reach around 40 m in height. On Haiwaii traces of ancient prehistoric tsunamis have been found that indicate a height of over 300 m. The troughs The size of the troughs between the waves depends on the way the waves were formed but they can can be as much as 160 km widee with a depth of only a few meters. The pictures below are not to scale as regards the height-to-width of tsunami waves!
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How a tsunami starts - in principle

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1. Before the earthquake:
The Indo-Australian has been sliding under the continental Eurasian plate for millions of years. The point where the Indo-Australian plate vanished below is Eurasian plate is the Sunda trench at at around 4,000 m depth. The movement of the two plates against each other averages at around 60-70 mm per year over the milennia but is not continuous. Tensions build up when no movement takes place over long periods and this tension is eventually released in an earthquake.
2. During the earthquake
The accumulated tensions are released suddenly. In the event of 26 December 2004, the Indo-Australian plate slipped around 20 m further below the Eurasian plate which in turn was lifted by about 5 m. Underwater landslides caused by the quake made a major contribution to the formation of the tsunami. The two large-scale movements set in motion an enormous amount of sea water. The colossal energy released by the adjustment of the two plates has been likened to the simultaneous explosion of 32,000 A-bombs of Hiroshima size. The waves generated by the earth movements 4,000 m below sea level spread mostly towards the west and northwest.
3. Tsunami waves travelling in deep water:
The giant waves are barely noticeable on the surface as long as they travel in seas more than 4,000 m deep. The trough between wave crests can be as much as 160 km with the crests less than 1 m. As tsunamis are generated at the bottom of the sea, they are large-wavelength waves in the open sea, travelling with speeds of 700-800 km/hwith minimum loss of energy.
4. Tsunami waves hitting land:
In shallow water, the tsunami waves slow down, rise from the normal sea surface and crowd together while becoming ever larger (see following graphics). Before hitting land, often (but not always) there is a "false ebb" when the sea temporarily withdraws before the giant waves arrive.
How the tsunami destroys - in principle

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The depth and topography of the sea determines the form a tsunami wave takes and how it propagates.
The way a tsunami breaks when reaching a coast is very difficult to predict. It depends on the topography that the wave has passed over on the high seas and on the form, steepness, height and form of the coastline hit. Within a few kilometers the hight of a tsunami wave can vary from lesss than a meter to 20 or more meters.

Light blue: normal sea level
Dark blue line: normal water surface
Dark blue: tsunami wave reaching higher than normal sea level
brown: land

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A wave is not "water moving"; it is energy passing through water, agitating the water molecules and then leaving the same molecules behind (except when a wave breaks on a coast when water is indeed moved briefly onto land).
The drawing illustrates the wave energy of a tsunami wave in the form of an oval. If the oval does not touch sea bottom, the wave will barely rise above the normal sea level (shown light blue). The shallower the sea is that the tsunami wave is passing through, the more the wave rises above the normal sea level (i.e. the wave amplitude increases), the more it slows down and the closer the waves crowd together (i.e. the higher the energy density becomes).
Light blue: normal sea level
Dark blue: tsunami wave reaching higher than normal sea level
brown: land

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week 5

Earth's structure

The earth consists of several layers. The three main layers are the core, the mantle and the crust. The core is the inner part of the earth, the crust is the outer part and between them is the mantle. The earth is surrounded by the atmosphere. Till this moment it hasn't been possible to take a look inside the earth because the current technology doesn't allow it. Therefore all kinds of research had to be done to find out, out of which material the earth consists, what different layers there are and which influence those have (had) on the earth's surface. This research is called seismology.

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Full size

Earth cutaway
Here, sections of the Earth have been removed to show its internal structure.

Image by: Colin Rose,
Dorling Kindersley

The core
The inner part of the earth is the core. This part of the earth is about 1,800 miles (2,900 km) below the earth's surface. The core is a dense ball of the elements iron and nickel. It is divided into two layers, the inner core and the outer core. The inner core - the center of earth - is solid and about 780 miles (1,250 km) thick. The outer core is so hot that the metal is always molten, but the inner core pressures are so great that it cannot melt, even though temperatures there reach 6700ºF (3700ºC). The outer core is about 1370 miles (2,200 km) thick. Because the earth rotates, the outer core spins around the inner core and that causes the earth's magnetism. More info...

The Mantle
The layer above the core is the mantle. It begins about 6 miles(10 km) below the oceanic crust and about 19 miles(30 km) below the continental crust (see The Crust). The mantle is to divide into the inner mantle and the outer mantle. It is about 1,800 miles(2,900 km) thick and makes up nearly 80 percent of the Earth's total volume. More info...
The Crust
The crust lays above the mantle and is the earth's hard outer shell, the surface on which we are living. In relation with the other layers the crust is much thinner. It floats upon the softer, denser mantle. The crust is made up of solid material but these material is not everywhere the same. There is an Oceanic crust and a Continental crust. The first one is about 4-7 miles (6-11 km) thick and consists of heavy rocks, like basalt. The Continental crust is thicker than the Oceanic crust, about 19 miles(30 km) thick. It is mainly made up of light material, like granite. More info...

- Plate Tectonics
- Earthquakes
- Volcanoes

The Atmosphere
The earth is surrounded by all kind of gases. This layer is called the earth's atmosphere. Without these atmosphere life on earth isn't possible. The atmosphere gives us air, water, warmth and is protecting us against harmful rays of the sun and against meteorites. This layer around the earth is a colorless, odorless, tasteless 'sea' of gases, water and fine dust. The atmosphere is made up of different layers with different qualities. It consists of 78% nitrogen, 21% oxygen, 0,93% argon, 0,03% carbon dioxide and 0,04% of other gases. The Troposphere is the layer where the weather happens, above this layer is the Stratosphere. Within the Stratosphere is the Ozone layer, that absorbs the Sun's harmful ultraviolet rays. Above the Stratosphere is the Mesosphere, the Thermosphere - in which the Ionosphere - and the Exosphere. The atmosphere is about 500 miles (800 km) thick. More info...
Influence of the Sun and the Moon
The sun and the moon both have their influence on the earth. Sometimes they cooperate and sometimes they counteract each other. Such influences are: the gravity, the warmth of the sun, the sunlight and the chronology. Through the gravitational force of the earth the moon orbits the earth. The moon also gravitates the earth, but less powerful. By the way gravity pulls the Earth and Moon toward each other, tides are caused (high tide and low tide). The sun also has some influence here. The sun brings light and is also responsible for the warming up of the earth

Nitrogen (N2)
780,840 ppmv (78.084%)
Oxygen (O2)
209,460 ppmv (20.946%)
Argon (Ar)
9,340 ppmv (0.9340%)
Carbon dioxide (CO2)
380 ppmv (0.0380%)
Neon (Ne)
18.18 ppmv (0.001818%)
Helium (He)
5.24 ppmv (0.000524%)
Methane (CH4)
1.79 ppmv (0.000179%)
Krypton (Kr)
1.14 ppmv (0.000114%)
Hydrogen (H2)
0.55 ppmv (0.000055%)
Nitrous oxide (N2O)
0.3 ppmv (0.00003%)
Xenon (Xe)
0.09 ppmv (9 × 10−6%)
Ozone (O3)
0.0 to 0.07 ppmv (0% to 7 × 10−6%)
Nitrogen dioxide (NO2)
0.02 ppmv (2 × 10−6%)
Iodine (I)
0.01 ppmv (1 × 10−6%)
Carbon monoxide (CO)
0.1 ppmv (0.00001%)Earth's atmosphere can be divided into five main layers. These layers are mainly determined by whether temperature increases or decreases with altitude. From highest to lowest, these layers are:
ExosphereThe outermost layer of Earth's atmosphere extends from the exobase upward. Here the particles are so far apart that they can travel hundreds of km without colliding with one another. Since the particles rarely collide, the atmosphere no longer behaves like a fluid. These free-moving particles follow ballistic trajectories and may migrate into and out of the magnetosphere or the solar wind. The exosphere is mainly composed of hydrogen and helium.ThermosphereTemperature increases with height in the thermosphere from the mesopause up to the thermopause, then is constant with height. The temperature of this layer can rise to 1,500 °C (2,730 °F), though the gas molecules are so far apart that temperature in the usual sense is not well defined. The International Space Station orbits in this layer, between 320 and 380 km (200 and 240 mi). The top of the thermosphere is the bottom of the exosphere, called the exobase. Its height varies with solar activity and ranges from about 350–800 km (220–500 mi; 1,100,000–2,600,000 ft).MesosphereThe mesosphere extends from the stratopause to 80–85 km (50–53 mi; 260,000–280,000 ft). It is the layer where most meteors burn up upon entering the atmosphere. Temperature decreases with height in the mesosphere. The mesopause, the temperature minimum that marks the top of the mesosphere, is the coldest place on Earth and has an average temperature around −85 °C (−121.0 °F; 188.1 K)[3]. Due to the cold temperature of the mesophere, water vapor is frozen, forming ice clouds (or Noctilucent clouds). A type of lightning referred to as either sprites or ELVES, form many miles above thunderclouds in the trophosphere.StratosphereThe stratosphere extends from the tropopause to about 51 km (32 mi; 170,000 ft). Temperature increases with height, which restricts turbulence and mixing. The stratopause, which is the boundary between the stratosphere and mesosphere, typically is at 50 to 55 km (31 to 34 mi; 160,000 to 180,000 ft). The pressure here is 1/1000th sea level.TroposphereThe troposphere begins at the surface and extends to between 7 km (23,000 ft) at the poles and 17 km (56,000 ft) at the equator, with some variation due to weather. The troposphere is mostly heated by transfer of energy from the surface, so on average the lowest part of the troposphere is warmest and temperature decreases with altitude. This promotes vertical mixing (hence the origin of its name in the Greek word "τροπή", trope, meaning turn or overturn). The troposphere contains roughly 80%[citation needed] of the mass
Layers of the atmosphere (not to scale)

Ammonia (NH3)
Not included in above dry atmosphere:
Water vapor (H2O)
~0.40% over full atmosphere, typically 1%-4% at surface

Structure of the atmosphere

Principal layers

WEEK 5 Different types of Natural disasters?
1.volcanic eruptions
2.sink holes