Page 110 - SST Class 07

Quiz Time districts of the country. There were more than 9000
Tick (3) the correct answer :
1. The magnitude of an earthquake is measured on
the seismograph /Richter scale .
2. The earth’s crust is made up of 15 major and
several large /minor plates.
3. The place right above the focus is called the
epicentre /tectonic movement.
4. The high waves of seawater which cause damage
are called earthquakes /tsunami .
Case Study : Devastating Earthquake of Nepal
On 25 April, 2015 at 11:41 AM, a devastating
earthquake occured in Nepal. The earthquake was
rated at 7.8 MW. Its epicentre was towards the east
of the district of Lamjung and its hypocentre was
at a depth of approximately 8.2 km. The location,
magnitude and focal mechanism of the earthquake
suggest that it was caused by slip along the main
frontal thrust. It was the worst natural disaster to
strike Nepal since the 1934 Nepal-Bihar
earthquake.
After this earthquake, continued aftershocks
occured throughout Nepal within 15-20 minute
intervals, with one shock reaching a magnitude of
6.7 on 26 April at 12:39 PM. The country also had a
continued risk of landslides. An another major
aftershock occurred on 12 May, 2015 at 12:36 PM
which was rated at 7.3 MW. Its epicentre was near
the Chinese border between the capital of
Kathmandu and Mount Everest. More than 200
people were killed and about 2500 people were
injured by this aftershock.
The earthquake triggered an avalanche on Mount
Everest, killing at least 19 people making April 25,
2015 the deadliest day on the mountain in history.
An another avalanche occured in Langtang Valley
located in Langtang National Park where 329
people reported missing after this avalanche which
hit the village on Ghodatabela and the village of
Langtang. The avalanche was estimated to have
been 2 or 3 km wide.
This devastating earthquake killed thousands of
people and made a large number of people
homeless with entire villages flattened across many
Contemporary Social Science-7
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people killed and more than 23,000 were injured in
Nepal.
Centuries old buildings were destroyed at UNESCO
World Heritage sites in the Kathmandu Valley,
including some at the Kathmandu Durbar Square,
the Patan Durbar Square, the Changu Narayan
Temple and the Swayambhunath Stupa.
Besides, the earthquake also affected some
neighbouring countries of Nepal like India where
about 130 people died and 560 were injured. In
China, about 27 people died and 383 were injured,
and in Bangladesh, where about 4 death and 200
injuries reported.
Geophysicists and other experts had warned for
decades that Nepal was vulnerable to a deadly
earthquake, particularly because of its geology,
urbanisation and architecture.
Activity
Collect pictures of the devastation that takes place
after an earthquake from newspapers/periodicals/
internet and paste them in your scrapbook.
MOVEMENT OF WATER, ICE AND WIND
The earth’s surface undergoes a change due to
weathering and erosion . The sun, wind, ice, water
or rain weather the surface and break it down. The
broken particles are carried away by erosion by
the movement of water, ice and wind. The
movement of water in rivers carries sediments with
it and deposits them in the plains. The movement
of ice in glaciers pushes rocks and broken stones
away, creating hollows. These hollows are filled
by melted ice and thus lakes are created. When
wind blows, you can see dust particles in it. The
broken particles of rocks are carried away by wind
from one place to another. This phenomenon can
be seen clearly in the deserts where sand dunes
shift from one place to another.
Landforms
The tectonic movements occurring within the
earth result in different landforms. These
movements are very gradual and occur in two
types—vertical movement and horizontal
movement.