Earth Quakes & Volcanoes

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Earth Quake

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“Shaking of earth, caused due to release of energy and generates waves that travel in all directions"

Types Of Earth Quakes.

Natural

1. Tectonic Earth Quakes

Tectonic Earth Quakes:

• Due to transform movement of tectonic plates
• Struck together while moving due to friction
• But breaks with force at focus and leading to release of energy all along fault region.

Man-made

1. Volcanic Earth Quakes
2. Collapse Earth Quakes[Mining]
3. Explosion Earth Quakes[Bombs]
4. Reservoir Induced Earth Quakes-No lower threshold on the size of reservoir 

Types of waves:

1. Body Waves
2. Surface Waves

Body waves: 

P-waves	S-waves
Dive through Solids,liquids & gases	Dive through Solids only
Shadow zone - Minimum	Shadow zone- Maximum

• So, 105-145 -identified as shadow zone of both waves

Surface waves:

• Body waves interact with surface rocks
• So,new set of waves generated
• Last to report
• Most Devastating 

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Intensity Vs Magnitude

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Earthquake events are scaled either according to the

Magnitude	Intensity
Energy released during Earth Quake	Damage caused by event
Measured by Ritchter scale	Measured by Mercalli
Range : 1-10	Range : 1-12

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Earthquake as a geomorphic agent:

• Ground Shaking
• Differential ground settlement
• Land and mud slides
• Soil liquefaction
• Ground lurching
• Avalanches

The above listed have some bearings upon landforms

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Volcano

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Types of Volcanoes:

1. Shield Volcanoes - largest - not steep
2. Composite Volcanoes - Pyroclastic material ,So Formation of layers
3. Caldera Volcanoes -most explosive -collapses themselves
4. Mid oceanic Ridge Volcanoes-Under Ocean

Volcanic Landforms:[Both Extrusive & Intrusive]

1. Plutonic rocks - lava cools under earth
2. Flood Basalt provinces - due to flow of lava -Deccan traps
3. Sills - Thicker horizontal bodies
4. Sheets - Thinner horizontal bodies
5. Dykes - perpendicular to planes
6. Batholiths - lava plane 
7. Lopoliths - saucer shape
8. Phacoliths - parallel to bending planes

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Locational Aspect of Earth quakes & Volcanoes:

1. Line of dots in the central parts of the Atlantic Ocean almost parallel tothe coastlines.
2. further extends into the IndianOcean.
3. It bifurcates a little south of the Indian subcontinent with one branch moving intoEast Africa and the other meeting a similar line from Myanmar to New Guiana.
4. line of dots coincides with the mid-oceanic ridges
5. shaded belt showing another area of concentration coincides with the Alpine-Himalayan system and the rim of the Pacific Ocean. 
6. the foci of the earthquake in the areas of mid-oceanic ridges are at shallow depths 
7. whereas along the Alpine-Himalayan belt as well as the rim of thePacific, the earthquakes are deep-seated ones.
8. The map of volcanoes also shows a similar pattern. 
9. The rim of the Pacific is also called rim of fire due to the existence of active volcanoes in this area.