- The theory of plate tectonics states that lithosphere consists of several individual segments called plates.
- Major Plates on Earth are.
(i) Antarctic plate
(ii) North American and South American
(iii) Pacific plate
(iv) Indian - Australian - New Zealand plate
(v)Africa/Eastern Atlantic Plate
(vi) Eurasian plate
- Pacific plate is the largest plate while Juan de Fucaplate (off Western coast of North America) is the smallest. -\
- The collision of the Indian plate against the Eurasian plate, leading to the formation of the Himalayas.
- An earthquake is basically the vibration of Earth produced by rapid release of energy, along a fault.
- Focus: Place of occurrence of anEarthquake inside the earth, where the energy is released. The ground ruptures at this spot, then seismic waves radiates outward in all direction.
- Epicenter: The point on the earth's surface is located directly above the focus of an earthquake.
- Seismic sensors called Seismographs, are located throughout the world can record the event.
- Earthquake waves: Earthquakes generate pulses of energy called Seismic waves that can pass through the entire Earth. These are –
- Primary (P) Waves: These waves travel both through solid crust and mantle and liquid part of the Earth's core.
- Secondary (S) waves: Travels only through solid parts of the Earth.
- Long (L) Waves: It is confined mostly to the skin of the Earth's crust, thereby, causing most of the structural damage.
- The magnitude as the intensity of energy released by an earthquake is measured by Richter scale. It ranges between 0 and 9.
Seismic Zones of India-
India is divided into 5 seismic zones.
- Zone 1 - Intensity V or below
- Zone 2 - Intensity VI
- Zone 3 - Intensity VII
- Zone 4 - Intensity VIII
- Zone 5 - Intensity IX and above
- A volcano is an opening or rupture in planet's crust through which hot magma, volcanic ash and gases escape from the magma chamber below the surface.
- Volcanic eruptions cause earthquakes when they erupt and sometimes earthquakes can cause volcanic eruptions.They mainly happen by the edges of tectonic plates.
Products of Volcanic eruption
- Flying Rocks
- Poisonous gases
- Pyroclastic flows
- Floods and Mudslides
On the basis of frequency of eruption the volcanoes can be divided into-
Active volcano: It has the capacity to erupt at regular basis and its frequency is quite more.
Dormant volcano: Though it has the capacity to erupt but frequency of eruption is almost nil.
Inactive volcanos don't have the capacity to erupt.