Write short note on lithospheric plates?
DIFFERENT LITHOSPHERIC PLATES
Identify the major lithospheric plates?
There are 7 major lithospheric plates. They are
} Pacific plate
} Australian plate
} North American plate
} South American plate
} Eurasian plate
} African plate
} Antarctic plate
Write short note on plates movement?
The lithospheric plates are situated above the
asthenosphere which is in a semi plastic state. Magma, which is a part of the
mantle remain molten due to the high temperature at the earth’s interior and
undergoes continuous convection. This causes the movement of lithospheric
plates. The plates move at a speed of 2 centimetres to 12 centimetres a year.
The speed of this movement has not always been uniform.
Explain different types of plate margins created by the movement of lithospheric plates.
Convergent margins
In convergent margins plates move towards each
other. Fold mountains are formed along the convergent margins. For example, the
Himalaya is a fold mountain range formed between the Indian plate and the
Eurasian plate. If there is any difference in density between the plates along
a convergent margin, the denser plate will submerge under the lighter one.
These zones are called subduction zones. Ocean trenches are developed in subduction
zones. The Challenger Deep in the Pacific Ocean is an example. Identify the
plates responsible for this.
Divergent margins
In divergent margins plates move away from each
other. A 14000-km long north-south oriented mountain range has been formed in
the Atlantic Ocean. This mountain range known as the Mid-Atlantic Ridge has
been formed as a result of the divergence of the above mentioned plates. Magma
comes out through the gap formed due to the divergence of plates and solidifies
to form mountains. These types of mountains are known as Mid Oceanic ridges.
Transform margins/ shear margins
In transform margins plates slide past each other.
Landforms are not generally created along the margins where the plates slide
past each other. But such margins are fault zones. The San Andreas Fault Zone
in North America is an example. As these
plate margins are weaker than other areas, such margins are generally
vulnerable to earthquakes, volcanoes, and faults.
What do you mean by uplift and subsidence?
Most landforms on the earth's surface are the
result of various earth movements. As a result of the earth movements, some
regions on the earth's crust are either raised or lowered. Raising of the
crustal portions are called uplift and lowering of the crust are called
subsidence.
What is
an earthquake?
Rocks in the deeper part of the earth undergo
displacement and faults due to plate movements and other causes. Under such
situations, severe pressure is exerted on the earth's lithosphere and seismic
waves are generated just like waves in a pond spreading in all directions when
a heavy object falls into it. These waves create tremors on the earth's
surface. These tremors are experienced by us as earthquake. Earthquakes may
occur due to the collapse of the roofs of mines, pressure in reservoir,
volcanic eruptions etc.
What do you mean by focus and epicenter of
earthquake?
The deep points inside the earth where the earthquake
occurs are known as focus and the point vertically above it on the earth's
surface is known as epicenter.
What are the different types of waves produced
from the focus during an earthquake? Which are the most destructive ones?
Three types of waves are produced from the focus
during an earthquake: primary waves, secondary waves and surface waves. The
surface waves are the most destructive ones.
Which is the instrument used to record seismic
waves?
Seismograph
What measures the intensity of energy released at
the time of an earthquake?
Richter scale
What is Tsunami?
Tremour waves originating due to earthquakes,
volcanic eruptions, meteor impact. etc. in the ocean floor generates huge sea
waves rising to several metres. Such waves are called Tsunamis.
We cannot avoid tsunamis. What are the mitigative
actions taken to reduce the impact of tsunamis?
Tsunami surveillance and warning systems are
widely in operation today. This system aims to identify the areas prone to
Tsunami and also to extend warning to the coastal areas so as to prevent loss of
life.
}
Recession in sea level may be an
indicator of Tsunami. If so, move on to safer locations.
} Take
official warnings seriously.
} Don’t arrive at self conclusion that the dangerous
situation is over, wait for official declaration.
} Once trapped by Tsunami waves try to escape
holding any floating materials firmly.
What are volcanoes?
The molten rock materials coming out through the fissures
along the plate margins are known as volcanoes.
What is the ‘specific ring of fire’?
Nearly 80% of the world's volcanoes are situated
around the Pacific Ocean. This zone containing more than 452 volcanoes is known
as 'the Pacific Ring of Fire'.
How are volcanoes useful to man?
} The soil formed by the weathering of lava rocks is fertile.
Example : the black soil of the Deccan plateau.
} Volcanic ash is a good manure.
} Geysers are formed in many volcanic regions. Such regions are being developed as tourist centers.
Example: the Old Faithful
Geyser, Yellow Stone National Park – North America.
.png)
.png)
.jpg)
.png)
.png)
.jpg)
.jpg)
.jpg)
0 Comments