Earthqu akes Earthqu akes & & Tsunam is Tsunam is By : By : Nirmal Roshan R Class : Class : 1

Earthquakes and tsunamis

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By : By : Nirmal Roshan R

Class : Class :



• Introduction• Focus & Epicenter• Seismologists• The Richter Scale• The Seismograph• Tsunamis• Major Volcanic & Earthquake Belts• The April 2015 Nepal Earthquake 

Remarks :


IntroductionIntroduction• Fault: a break in the

Earth’s crust.• Blocks of the crust slide

past each other along fault lines.

• When rocks that are under stress suddenly break, a series of ground vibrations is set off.These vibrations are known as earthquakes.

• Earthquakes occur all the time.


Focus & EpicenterFocus & Epicenter

• The point beneath the surface where the rocks break and move is called the focus. The focus is the underground origin of an earthquake.

• Directly above the focus, on the Earth’s surface is the epicenter. Earthquake waves reach the epicenter first. During an earthquake, the most violent shaking is found at the epicenter.




• Seismologists study earthquakes. They can determine the strength of an earthquake by the height of the wavy line recorded on the paper.

• The seismograph record of waves is called a seismogram.

• The Richter scale is used to calculate the strength of an earthquake.


The Richter Scale

• Used by scientists to quantify the amount of energy released by an earthquake.

• Magnitude: The measure of the energy released by an earthquake.

• The scale goes from 1.0 to 10.0.

• Each increase of magnitude by one whole number is ten times greater and releases 31.7 times more energy than the whole number below it.


The SeismographThe Seismograph

• A weight attached to a spring remains nearly still even when the Earth moves. A pen attached to the weight records any movement on a roll of paper on a constantly rotating drum. The drum moves with the Earth and affects the line.




• Earthquakes which occur on the ocean floor produce giant sea waves called tsunamis. Tsunamis can travel at speeds of 700 to 800 km per hour. As they approach the coast, they can reach heights of greater than 20 meters.


How a Tsunami How a Tsunami FormsForms


Major Volcanic & Major Volcanic & Earthquake BeltsEarthquake Belts

Ring of FireRing of Fire• One major earthquake and

volcano zone extends nearly all the way around the edge of the Pacific Ocean. This zone goes through New Zealand, the Philippines, Japan, Alaska and along the western coasts of North and South America. The San Andreas fault is part of this zone.


Mediterranean ZoneMediterranean Zone

• A second Major earthquake and volcano zone is located near the Mediterranean Zone and extends across Asia into India. Many countries in the zone, including Italy, Greece and Turkey, have violent earthquakes. Many volcanic eruptions also occur in this zone.


Mid-Atlantic Ridge Mid-Atlantic Ridge ZoneZone

• The third major earthquake and volcano zone extends through Iceland and to the middle of the Atlantic Ocean. There is under the ocean a long range of volcanic mountains called the Mid-Atlantic Ocean Range. Scientists believe that the volcano and earthquake activity are due to the formation of new parts of the Earth’s crust along the ridge. The volcanic island of Iceland is part of this zone.


The The April 2015 Nepal April 2015 Nepal EarthquakeEarthquake  

(The (The Gorkha EarthquakeGorkha Earthquake))

• Thousands of people lost their lives and thousands more were injured in a 7.8-magnitude earthquake that hit Nepal's capital Kathmandu and its surrounding areas on 25 April.

• The earthquake was followed by a large number of aftershocks, including one that measured 7.3 on 12 May.

• Among the worst-hit districts was Sindhupalchok - where more than 2,000 died. In the capital, Kathmandu, more than 1,000 perished. Thousands more were badly injured by falling debris caused by the quake or powerful aftershocks that rocked the region. Mount Everest was also struck by deadly avalanches after the quake on 25 April.


• The United Nations, which estimates 6.6 million people live in the districts affected by the earthquake, is helping to co-ordinate rescue efforts.

• Many have been left homeless by the disaster and the country is already reported to be running out of water and food. There are also frequent power cuts.

• The British organisation, Search and Rescue Assistance in Disasters (SARAID) has sent a team of experts with 1.5 tonnes of specialist equipment. This includes an electrical power generator and power tools for cutting through concrete and steel.

• They also have their own tents and food supplies, so they will not be a drain on local resources.

• India and China are among the other countries to send teams of rescuers.




Earthquake BeltsEarthquake BeltsOf The WorldOf The World