Geography - Earthquakes & Tsunamis

1. Earthquakes
Earthquakes
&&
Tsunamis
Tsunamis
By :By : Nirmal Roshan R
Class :Class :
11

2. IndexIndex
• Introduction
• Focus & Epicenter
• Seismologists
• The Richter Scale
• The Seismograph
• Tsunamis
• Major Volcanic & Earthquake Belts
• The April 2015 Nepal Earthquake
Remarks :
22

3. 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.
33

4. Focus &Focus &
EpicenterEpicenter
• 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.
44

5. 55

6. SeismologistsSeismologists
• 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.
66

7. 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.
77

8. 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.
88

9. 99

10. TsunamisTsunamis
• 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.
1010

11. How a TsunamiHow a Tsunami
FormsForms
1111

12. 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.
1212

13. MediterraneanMediterranean
ZoneZone
• 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.
1313

14. Mid-Atlantic RidgeMid-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.
1414

15. TheThe April 2015 NepalApril 2015 Nepal
EarthquakeEarthquake
(The(The GorkhaGorkha
EarthquakeEarthquake))
• 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.
1515

16. • 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.
1616

17. 1717

18. 1818

19. Earthquake BeltsEarthquake Belts
Of The WorldOf The World
1919