Landslide Induced Earthquake in Greenland | 26 Sep 2024

Source: TH

Why in News?

Recently, scientists detected unusual seismic waves around the world caused due to landslides in Greenland that lasted nine days. 

• Unlike typical earthquake signals (P and S waves), these waves exhibited a single frequency, suggesting a non-seismic origin.
• Seismologists initially labelled the phenomenon as a “USO” (Unidentified Seismic Object) due to its mysterious nature.

What are the Key Facts About this Landslide-Induced Earthquake?

• Origin: By analysing seismic data, satellite images, water level monitors, and simulations, scientists discovered that a large landslide in Dickson Fjord, Greenland, triggered the event.
  • The collapse of Hvide Stovhorn peak led to a rock-ice avalanche, triggering a submarine landslide.
• Seiche Effect in the Fjord: In the confined fjord, waves bounce between its walls, creating a phenomenon known as a “seiche.” 
  • This back-and-forth sloshing persisted for over nine days, with waves oscillating every 90 seconds.
• Tsunami: The earthquake gave rise to a 200-metre-high mega-tsunami at an isolated place in the Arctic Ocean region. It didn’t kill anyone but it damaged an unstaffed research facility on the island of Ella.
• Global Reverberations: The seiche waves sent seismic signals across the globe causing Earth’s surface to vibrate. 
  • This prolonged reverberation was detected on seismometers from the Arctic to Antarctica.
• Link to Climate Change: The landslide occurred because the glacier at the fjord's foot melted and retreated due to global warming, leaving the rocky slope unsupported and causing it to collapse.
  • It underscores the impact of climate change in polar regions, where warming accelerates ice melt, destabilising landscapes.

What are Fjords?

• About: Fjords are elongated, deep, narrow steep-sided inlets of the sea that extend far inland and are formed due to the inundation of a glaciated valley.
  • Fjords are found in mountainous areas of both the Northern and Southern Hemispheres, particularly in the higher latitudes (up to about 80O).
• Formation of Fjords: Fjords were formed during the last Ice Age by glaciers. As glaciers moved slowly, they carved out deep valleys, leading to the creation of fjords. 
  • Fjords are deepest inland because the glacier's force was strongest there during glaciation.

• Geographic Distribution of Fjords: Fjords are primarily found in Norway, Chile, New Zealand, Canada, Greenland, and Alaska.
• Coral Reefs in Fjords: Some fjords, particularly in Norway, host deep cold-water coral reefs, which support various marine species like fish, plankton, and sea anemones. 
  • These cold-water reefs thrive in complete darkness and under extreme pressure, unlike their tropical counterparts.
• Skerries (Rocky Islands): Skerries are small rocky islands found around fjords, formed by glaciation. They are common along the Scandinavian coastline.
• Fjords as Calm Harbours: Despite the rocky islands or skerries that can make navigation difficult, fjords are generally calm and protected. This makes them ideal harbours for ships due to their tranquil waters.