Note4Students
From UPSC perspective, the following things are important :
Prelims level: Greenland Landslide, Dickson Fjord
Why in the News?
- In September 2023, seismic stations across the world detected an unusual signal which persisted for 9 days.
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- It was caused by a massive landslide in Greenland’s Dickson Fjord (i.e narrow sea inlet with steep sides or cliffs, created by a glacier).
About the Massive Greenland Landslide
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Causes of the Greenland Landslide
- The main reason for the landslide was global warming, which caused the glaciers in Greenland to melt and shrink over recent decades.
- The Hvide Stovhorn peak glacier had been holding up the mountain slopes, but as it thinned, the rock above it became unstable and eventually collapsed.
- The permafrost (frozen ground) on the mountain’s steep slopes started melting because of rising temperatures, making the slopes unstable.
- When the rocks and ice fell into the fjord, it triggered a submarine landslide (a landslide under water), which made the event even bigger and caused a mega-tsunami.
Back2Basics: Seismic Waves
Type | Sub-Type | Wave Characteristics | Speed | Medium of Travel | Movement | Impact |
Body Waves | P-Waves (Primary Waves) | • Longitudinal/compressional waves. • Fastest seismic waves. |
Fastest (First to arrive) | Solids and liquids | Particles move back and forth in the direction of wave travel. | First waves to be detected during an earthquake, cause less damage. |
S-Waves (Secondary Waves) | • Transverse/shear waves. • Slower than P-waves. |
Slower than P-Waves | Solids only | Particles move perpendicular to the wave’s direction. | Follow P-waves, more ground shaking, cause more damage than P-waves. | |
Surface Waves | Love Waves | • Transverse horizontal motion. • Faster than Rayleigh waves. |
Slower than S-Waves | Earth’s surface | Particles move side to side, horizontally. | Cause significant structural damage. |
Rayleigh Waves | • Rolling motion. • Slowest seismic waves. |
Slowest of all seismic waves | Earth’s surface | Particles move in an elliptical motion (both vertical and horizontal). | Cause vertical and horizontal ground movement, highly destructive. |
PYQ:[2021] Describe the various causes and the effects of landslides. Mention the important components of the National Landslide Risk Management Strategy. |
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