NCERT 5th Class (CBSE) Science: Volcanoes, Earthquakes and Tidal Waves

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Question: What are volcanoes?

Answer: Cracks in the earth’s crust out of which molten magma comes out is called volcanoes.

Question: Name three types of volcanoes?

Answer: The three types of volcanoes are:

Active Volcanoes
Dormant Volcanoes
Extinct Volcanoes

Question: Give one example each of an active and an extinct volcanoes.

Answer: The examples are:

Active Volcanoes – Mount Fuji
Extinct Volcanoes – Zuidwal Volcano

Question: What is an earthquake? How is it caused?

Answer: A sudden movement of a part of the Earth’s surface is called earthquake. They are caused by severe shock waves that travel through the solid rocks from the Earth’s crust to the surface.

Question: Give one example of an epicentre and an aftershock of an earthquake in India.

Answer: The example is:

During the Gujarat earthquake of 2001, Bhuj was the epicenter. In the Kashmir earthquake of 2005, aftershock were felt for many days.

Question: What does a seismography measure?

Answer: Seismograph is used to measure and record the intensity, direction and duration of earthquakes.

Question: Write one difference between tidal wave and a tsunami?

Answer: Tidal Wave – It is the rise and fall of sea level. It is caused by the gravitational forces acting between the sun, moon and earth.

Tsunami – These are caused by undersea earthquakes, volcanic eruptions, landslides etc.

Question: Describe the three kinds of volcanoes.

Answer:

Active Volcanoes

Dormant Volcanoes

Extinct Volcanoes

Active volcanoes are those that may erupt at any time or have erupted in the past. Many active volcanoes are found around the Pacific Ocean giving rise to the name “The Pacific Ring of Fire”. For example Mt. Etna in Italy.

Those volcanoes that have not erupted for many years but have chances of erupting again. When a vent becomes blocked by a hardened lava plug, it becomes a dormant volcano. These are also known as sleeping volcanoes. For example Fujiyama in Japan.

Those volcanoes that are not erupted for thousands of years and probably never will are called extinct volcanoes. They are also known as dead volcanoes. For example Mt. Kilimanjaro in Africa.

Question: What are focus, epicenter and aftershocks?

Answer:

Focus

Epicenter

Aftershocks

The point under the ground where the earthquake begins is called Focus.

The spot corresponding to the focus on the Earth’s surface is called Epicenter.

After the first big quake, smaller quakes or tremors may continue to occur is called aftershocks.

Question: Mention any three effects of an earthquake.

Answer: The three effects of an earthquake are:

An earthquake, especially a strong one, always causes destruction of property. Buildings may develop cracks or even fall down. Roads and bridges get damaged. Trees get uprooted. Many lose their lives too by getting trapped under the heavy slabs that have fallen etc.
An earthquake, especially an undersea one, can cause other disasters like tsunami.
It can cause landslides and fires.

Class Notes NCERT Solutions for CBSE Students