2nd GROUP

“TSUNAMI”

Created by :

Novi Dian Anggraeni (270110110027)

Novita Wulandari (270110110028)

Kuat Yogiristanto (270110110030)

Dwi Menur Mandriati S (270110110150)

Gerson Yosef (2701101100048)

Luis Hideyoshi (270110110128)

Achmad Chaidar (270110110130)

Riza Hurqani

Riza Rahmatan

Adika

Wawan Septian

CLASS : GEOLOGY B

FACULTY OF GEOLOGICAL ENGINEERING

PADJADJARAN UNIVERSITY

DAFTAR ISI

TSUNAMI

I. What is Tsunami

The word tsunami (pronounced soo-NAH-mee) is Japanese, and it means

‘harbour wave’.

A tsunami is a huge volume of moving seawater. These giant waves can

travel for thousands of miles across the sea and still have enough energy and

force to destroy buildings, trees, wildlife and people.

If you throw a stone in a pond it will create a series of ripples.  A tsunami is

just like those ripples but the disturbance that sets them moving is much

greater than a small stone.  It can be triggered by an undersea earthquake,

landslide or volcanic eruption.

In deep water tsunami waves can extend thousands of feet into the sea,

and reach speeds of 500 mph, almost fast enough to keep up with a jet

airplane.  There can be up to a hundred miles between each wave, which may

be just a few feet above the sea.

Besides on Picture 1.1, This image shows sediment (light brown & green

colour) left after the tsunami along the northeast coast of Sri Lanka.

Most Tsunamis are caused by undersea earthquakes.  These underwater

earthquakes cause disruption to the seafloor and, in turn, the overlying water. 

A tsunami and has nothing to do with tides although it is sometimes mistakenly

called a tidal wave.

How and where do these undersea earthquakes occur? 

The earth is made up of several pieces of hard rock that fit together a bit

like a jigsaw.  These are called tectonic plates and they move very slowly. 

Oceanic plates are denser/heavier than continental plates and so they slide

under the continental plates.  Where this happens it is called a subduction

zone.  There are subduction zones off Chile, Nicaragua, Mexico and

Indonesia.  These areas are prone to earthquakes, which happen when the

plates suddenly move against each other.

What other things could create a tsunami?

Sometimes when an ocean island collapses it causes a huge

displacement of water which can also create a tsunami.  Very rarely, a tsunami

can be created by a giant meteor hitting the sea.

Scientists found traces of a huge meteor rock that collided with the Earth

3.5 billion years ago and landed in the sea, which may have created a giant

tsunami that drastically changed coastlines and wiped out almost all life on

land.

II. What Causes Tsunami

A tsunami is a large ocean wave that is caused by suddenly motion on the

ocean floor. This sudden motion could be an earthquake, a powerful volcanic

eruption, or an underwater landslide. The impact of a large meteorite

could also cause a tsunami. Tsunamis travel across the open ocean at great

speeds and build into large deadly waves in the shallow water of a shoreline.

Subduction Zones are Potential Tsunami Locations

Most tsunamis are caused by earthquakes generated in a subduction

zone, an area where an oceanic plate is being forced down into the mantle by

plate tectonic forces (Picture 1.2). The friction between the subducting plate

and the overriding plate is enormous. This friction prevents a slow and steady

rate of subduction and instead the two plates become "stuck".

Accumulated Seismic Energy

As the stuck plate continues to descend into the mantle the motion causes

a slow distortion of the overriding plage (Picture 1.3). The result is an

accumulation of energy very similar to the energy stored in a compressed

spring. Energy can accumulate in the overriding plate over a long period of time

- decades or even centuries.

Earthquake Causes Tsunami

Energy accumulates in the overriding plate until it exceeds the frictional

forces between the two stuck plates (Picture 1.4). When this happens, the

overriding plate snaps back into an unrestrained position. This sudden motion

is the cause of the tsunami because it gives an enormous shove to the

overlying water. At the same time, inland areas of the overriding plate are

suddenly lowered.

Tsunami Races Away From the Epicenter

The moving wave begins travelling out from where the earthquake has

occurred (Picture 1.5). Some of the water travels out and across the ocean

basin, and, at the same time, water rushes landward to flood the recently

lowered shoreline.

Tsunamis Travel Rapidly Across Ocean Basis

Tsunamis travel swiftly across the open ocean (Picture 1.6). The map

below shows how a tsunami produced by an earthquake along the coast of

Chile in 1960 traveled across the Pacific Ocean, reaching Hawaii in about 15

hours and Japan in less than 24 hours.

Tsunami "Wave Train"

Many people have the mistaken belief that tsunamis are single waves.

They are not. Instead tsunamis are "wave trains" consisting of multiple waves.

The chart below is a tidal gauge record from Onagawa, Japan beginning at the

time of the 1960 Chile earthquake. Time is plotted along the horizontal axis

and water level is plotted on the vertical axis. Note the normal rise and fall of

the ocean surface, caused by tides, during the early part of this record. Then

recorded are a few waves a little larger than normal followed by several much

larger waves. In many tsunami events the shoreline is pounded by repeated

large waves.

III. The Case of Tsunami in Aceh, December 26th 2004

On 26th December 2004, a devastating tsunami hit Indonesia and

affected several countries.  The tsunami was caused by an underwater

earthquake which measured 9.15 on the Richter scale.  Among the affected

countries was Somalia in Africa which is almost 3000 miles from the epicenter

of the earthquake.

The initial tsunami waves took a little over 2 hours to reach the teardrop-

shaped island of Sri Lanka.  Additional waves continued to arrive for many

hours afterward.

NASA's Terra satellite passed overhead capturing this image of deep sea

tsunami waves about 30-40 kilometers from Sri Lanka's southwestern coast. 

The image covers an area of 129 miles x 128 miles (Picture 1.7).

IV. How We Save Lives

Be aware of tsunami facts. This knowledge could save your life. There are

several ways to protect your self from tsunami.

If you are in school and you hear there is a tsunami warning, you should

follow the advice of teachers and other school personnel.

If you are at home and hear there is a tsunami warning, you should make

sure you entire family is aware of the warning. Your family should evacuate

your house if you live in a tsunami evacuation. Move in an orderly, calm and

safe manner to the evacuation site or to any safe place outside your

evacuation zone. Follow the advice of local emergency and law enforcement

authorities.

If you are at the beach or near the ocean and you feel the earth shake, move

immediately to higher ground. Do not wait for a tsunami warning to be

announced. Stay away from rivers and streams that lead to the ocean as you

would stay away from the beach and ocean if there is a tsunami. A regional

tsunami from a local earthquake could strike some areas before a tsunami

warning could be announced.

Tsunamis generated in distant locations will generally give people enough

time to move to higher ground. For locally generated tsunamis, where you

might feel the ground shake, you may only have a few minutes to move to

higher ground.

High, multi-story, reinforced concrete hotels are located in many low-lying

coastal areas. The upper floors of these hotels can provide a safe place to

find refuge should there be a tsunami warning and you cannot move quickly

inland to higher ground. Local Civil Defense procedures may, however, not

allow this type of evacuation in your area. Homes and small buildings located

in low lying coastal areas are not designed to withstand tsunami impacts. Do

not stay in these structures should there be a tsunami warning.

Offshore reefs and shallow areas may help break the force of tsunami waves,

but large and dangerous waves can still be threat to coastal residents in

these areas. Staying away fro all low-lying coastal areas is the safest advice

when there is a tsunami warning.

If You Are on a Boat or Ship

Since tsunami wave activity is imperceptible in the open ocean, do not return

to port if you are at sea and a tsunami warning has been issued for your

area. Tsunamis can cause rapid changes in water level and unpredictable

dangerous currents in harbors and ports.

If there is time to move your boat or ship from port to deep water (after you

know a tsunami warning has been issued), you should weigh the following

considerations:

o Most large harbors and ports are under the control of a harbor

authority and/or a vessel traffic system. These authorities direct

operations during periods of increased readiness (should a tsunami be

expected), including the forced movement of vessels if deemed

necessary. Keep in contact with the authorities should a forced

movement of vessels be directed.

o Smaller ports may not be under the control of a harbor authority. If you

are aware there is a tsunami warning and you have time to move your

vessel to deep water, then you may want to do so in an orderly

manner, in consideration of other vessels. Owners of small boats may

find it safest to leave their boat at the pier and physically move to

higher ground, particularly in the event of a locally generated tsunami.

Concurrent severe weather conditions (rough seas outside of safe

harbor) could present a greater hazardous situation to small boats, so

physically moving yourself to higher ground may be the only option.

o Damaging wave activity and unpredictable currents can effect harbors

for a period of time following the initial tsunami impact on the coast.

Contact the harbor authority before returning to port making sure to

verify that conditions in the harbor are safe for navigation and

berthing.

V. The Facts of Tsunami

The Pacific Ocean experiences more tsunamis than anywhere else in the

world.  Tsunamis have also occurred in the Caribbean and Mediterranean

Seas, and the Indian and Atlantic Oceans.

The December 2004 Asian tsunami is the deadliest in recorded history with a

death toll of nearly 300,000.  It was triggered by the fourth most powerful

earthquake since 1900, estimated to measure 9.15 on the Richter scale.

Many people were killed by the Asian tsunami because they went down to the

beach to see the exposed seafloor caused by the retreating of the sea.  If you

see the sea receding unusually quickly or far it’s a good sign that a big wave

is on its way.

Before 2004 the most damaging tsunami on record was in 1782, following an

earthquake in the South China Sea, which killed an estimated 40,000 people.

The Indian Ocean tsunami travelled as much as 3,000 miles to Africa and still

had enough force to cause enormous destruction. For example, Somalia was

hit harder than Bangladesh despite being much further away.

An earthquake off the coast of Chile in 1960 produced a tsunami that had

enough force to kill 150 people in Japan after a journey of 22 hours and

10,000 miles.

In 1775, the Lisbon earthquake created a tsunami in the North Atlantic that

killed as many as 60,000 people in Portugal, Spain and North Africa.  This

quake caused a tsunami as high as 23 feet in the Caribbean.

Another of the most deadly tsunamis in recorded history followed the eruption

of the volcano Krakatoa in 1883, which destroyed the volcano completely and

killed more than 36,500 people across the South Java Sea.

VI. Conclusion

A tsunami is a huge volume of moving seawater. Tsunami waves can travel

for thousands of miles across the sea and still have enough energy and force to

destroy buildings, trees, wildlife and people. Tsunami could be happened

because of several causes, example : earthquake, a powerful volcanic

eruption, underwater landslide, and also the impact of a large meteorite. We

should learn more about the ways to save our self from tsunami ways to protect

us if this disaster suddenly occurs.

Daftar Gambar

Picture 1.1 Picture 1.2

Picture 1.3 Picture 1.4

Picture 1.5

Picture 1.6

Picture 1.7

DAFTAR PUSTAKA