Geography Series 4

Geography Series 4



Hey Guys, What’s up? In the last 3 articles, we have covered basics of Geography.
Today, we will begin with interior of Earth.
•Radius of earth is 6370 Km.
•2 sources tell us about earth’s interiors◦Direct Sources –◾Rocks at mining areas viz Gold mines in South Africa 3 km deep, “Deep Ocean Drilling Project” & “Integrated drilling ocean project” at Kola in Arctic Ocean- 12 km deep;
◾Volcanic eruptions.
◦Indirect Sources –◾Seismic Activity,
◾Meteors,
◾Gravitation- more near poles and less at equator (as distance from center at equator is more than at the poles)
◾Magnetic Field.

Earthquake waves are of two types:
earthquake
Body waves generated due to release of energy at focus & move in all directions throughout body of earth. They are of two types:
•P-waves also known as Primary Waves –◦Faster & 1st to arrive at surface.
◦Similar to sound waves i.e. vibrate parallel to direction of the wave.
◦Travel through solid, liquid or gaseous medium
•S-waves or secondary waves –◦Arrive at surface after some time.
◦Travel only through solid medium
◦Vibrate perpendicular to direction of motion.

earthquake
•Surface waves –◦generated by interaction of body waves with surface of earth;
◦they are last to report on seismograph
◦Vibrate perpendicular to direction of motion.
◦Most destructive.

Emergence of Shadow Zone:

earthquake
•There are some areas where waves are not reported which are known as Shadow Zones.
•For each earthquake different shadow zone.
•Seismographs located at any distance within 105o from epicenter recorded arrival of both P and S waves.
•Seismographs beyond 145o recorded arrival of P waves & not S waves.
•So, entire zone beyond 105o is a shadow zone of S wave (which is little more than 40% of entire earth surface) & zone between 105o & 145o is a shadow zone of P waves
•Types of Earthquake
earthquake
Earthquake Measurement:
1.Ritcher Scale – measures magnitude scale i.e. energy released during the quake. It is expressed in absolute numbers, 0-10.
2.Mercalli Scale – measures intensity scale i.e. visible damage caused. The range is from 1-12.
This was all about the Earthquake. The next article will cover Structure of the Earth & Volcanic Landforms.