Eduqo
Indian Geography›Ch 1: Earth & Universe›Earthquakes, Volcanoes and Plate Tectonics
Master seismic waves, Richter scale, Ring of Fire and volcano types for competitive exams
The Earth's lithosphere is broken into major and minor plates that float on the asthenosphere, causing earthquakes and volcanic activities along their boundaries.
Smart Memory Hooks
| Wave Type | Nature / Motion | Medium Allowed |
|---|---|---|
| P-Waves | Longitudinal | Solid, Liquid, Gas |
| S-Waves | Transverse | Solid only |
| L-Waves | Surface wave | Surface only |
Epicentre
(Point above focus)
Point above focus
Epicentre lies directly above the seismic focus on Earth's surface.
Richter Scale
(Logarithmic magnitude)
Logarithmic magnitude
Each whole number increase represents a 10-fold amplitude rise.
Shield Volcano
(Basaltic lava cone)
Basaltic lava cone
Mauna Loa in Hawaii is a classic example of a shield volcano.
Ring of Fire
(Pacific seismic belt)
Pacific seismic belt
It accounts for over 75 percent of the world's active volcanoes.
Richter scale measures energy directlyMeasures amplitude logarithmically
Energy release is actually calculated using moment magnitude; Richter measures wave amplitude.
S-waves pass through outer coreS-waves cannot pass liquid outer core
Outer core is liquid, which completely stops transverse secondary waves.
Volcanoes occur only at plate boundariesHotspot volcanoes occur inside plates
Hotspots like Hawaii or Reunion Island form volcanoes away from plate edges.
Q1.Which seismic wave is completely blocked by the Earth's liquid outer core?
Q2.The Pacific Ring of Fire is best known for which of the following?