The formation of tsunamis and earthquakes

1.Earthquakes
1. According to dictionary.reference.com an earthquake is a:
Series of vibrations induced in the earth's crust by the abrupt rupture and rebound of rocks in which elastic strain has been slowly accumulating.
The earth is made up of tectonic plates these are massive slabs of rock floating on magma ,as the plates move about, they spread apart, collide, or slide past each other, This is the main cause of volcanoes and earthquakes
Earthquakes occur in many regions all over the world in some regions they occur more frequently and severely than in others (depending on the location), the main cause of earthquakes is tectonic plates grinding against each other , therefore earthquakes occur more frequently and more severely in these regions , less commonly earthquakes are caused by volcanic activity in this case they either proceed or ac company eruptions . Volcanoes
Volcanoes are formed when plates collide or move away from one another thus they are usually found at the edge of tectonic plates .Volcanoes can also occur in the interior of plates, these volcanoes are commonly known hotspots.

MOVEMENT OF TECTONIC PLATES

2. Tsunamis can be formed by :

Underwater earthquakes
Underwater earthquakes are the most common cause of tsunami’s .If an underwater earthquake is large enough, significant movements will be made by the ocean floor, pushing up the ocean water upward causing a large ripple that begins to travel through the ocean at a speed of 600miles/h. because the ocean is so deep, the wave is not limited by space resulting in plenty of room to move around, as it gets nearer to the shore the wave size increases in height as the water becomes shallower . Eventually the wave will hit the shore and travel further inland.

Volcanoes

There are three different ways that volcanoes can cause tsunamis : a land-based volcano can break down and collapse, forcing large amounts of ash and rubble into the water. This sudden change and displacement of the water column transfers to kinetic energy (movement energy) and results in waves. More debris can create a bigger increase in wave size and amount.
An offshore or submarine volcanic eruption can create high magnitude lifts on seafloors, which pushes large water columns upwards creating a tsunami.
The collapsing of a submarine volcano's slope creates a sudden disturbance in the water resulting in tsunami waves.

Landslides
Tsunamis are often generated by a submarine landslide, which usually occurs because of an earthquake, (shaking unsettles coral, rock, or ice formations causing them to fall). A submarine landslide, rock fall, or ice fall can trigger a tsunami by displacing large amounts of water. This causes a rise in water levels, generating a tsunami.

Why tsunamis are so dangerous
2.1 Tsunamis can come quickly with little warning they can't be seen until they hit shore with a powerful force. Locally generated tsunami may reach a nearby shore in less than ten minutes due to their high speeds therefore there might not be enough time for the Pacific Tsunami Warning Centre or for local authorities to issue a warning. Dangerous waves often follow the first tsunami wave, trapping people who return, thinking the tsunami is over.
3. How earthquakes form
Most earthquakes occur due to movement tectonic plates these are massive slabs of rock floating on magma ,as the These plates are in continuous movement. This movement eventually causes collision among the plates. Stress builds up on the lithosphere. This stress causes a break or shift in the crust. When the stress is released the energy starts moving from one place to another in the form of waves (called seismic waves). These waves shake the earth and causes an earthquake. Sometimes the stress occurs near the centre of the plate, but mostly it occurs on the edges. Here two plates collide or goes over or into another plate. This causes different types of earthquakes of different magnitudes. When two tectonic plates slide past one another huge amounts of energy is built up . image from http://www.stmarysmedia.co.uk/jb11/project/CausesofEarthquakes.htm

Earthquake Detection
Earthquake prediction
Despite considerable research efforts by seismologists we still cannot at this stage predict earthquakes to day month or year, however, for well-understood faults the probability that a segment may rupture during the next few decades can be estimated. Many phenomena are considered to be possible precursors of earthquakes, and among those under investigation are seismicity, changes in the ionosphere, various types of electromagnetic indicators including infrared and radio waves, radon emissions, and even unusual animal behaviour.
Earthquake warning systems
Currently people detect earthquakes by monitoring seismic activity. Earthquake warning systems consist of seismic motion sensors arranged throughout a region. High speed communications systems and computers collect the sensor readings and the computers are programmed to detect the likely strength and progression of the seismic event. If a dangerous event is detected then alarms can be signalled through the region likely to be affected, allowing warnings before local ground motion of up to and beyond twenty seconds. While short, such warnings would be sufficient to allow many people to move to safer areas or to take shelter.

4. How volcanoes form

1. Volcanoes most commonly occur where two tectonic plates meet. When two tectonic plates converge they create a gap/ fissure hot molten rock (magma) then rises up through the fissure .This type of volcano mainly occurs on the ocean floor where it is difficult to spot.
2. If two tectonic plates converge one plate is forced beneath the other this results in massive amounts of friction, creating immense heat causing magma to to liquefy and rise up in the form of lava eruptions by these volcanoes create the most violent and dangerous eruptions as friction greatly increases temperatures causing gases to expand creating immense amounts of pressure Few volcanoes were formed in this manner, but their eruptions are very violent and dangerous ones throwing the lava out with great force, and to great heights. Fortunately only a few volcanoes on earth were formed like this.
3. Volcanoes can form in the middle of tectonic plates these are formed by normal tectonic movement where magma is pushed up little by little until it enters cracks in the rock of the lithosphere .Volcanoes are not always formed if this is the case ,however, if the overlying rocks are brittle, they give away to allow the magma to flow out onto the Earth's surface in the form of lava. These volcanoes are commonly known as hotspots ,these are places that are connected by channels to the mantle of the earth.

Image from http://img. tfd.com/hm/JPG/A4syncli.jpg

Terminology Dictionary definitions from http://www.thefreedictionary.com/ anticlinesplural of an·ti·cline
Noun:

synclinesplural of syn·cline
Noun:
A trough or fold of stratified rock in which the strata slope upward from the axis.

LANDFORMS FORMED BY FAULTING
BLOCK MOUNTAIN (HORST)
Block mountains are formed when faulting in the crust due to either tension or compression causes a block of the crust to be uplifted,
RIFT VALLEY (GRABEN): rift valleys are the reverse of block mountains(horst), they are formed by tension, compression or parallel faults

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