Continental Plates and Volcanism

In Context

• Slowing of continental plate movement was noted according to a new study published in Science Advances.

More about the study

• Slowdown of continental plates in the past:
  • A slowing of continental plate movement may have been the critical event that drove some of Earth’s most devastating extinction events.
    • Researchers used models to reconstruct the location of continents in different periods. 
    • After comparing these models with the age of volcanic activity, they observed that the continents moved at less than two centimetres per year.
• Potential slowdown in the future:
  • In the future, there is a possibility that continental plates may slow down, potentially triggering volcanic activities, according to researchers.
    • It may be challenging to predict in detail where and when that may happen.
• The process of slowdown and volcanism:
  • The slowdown in movement of continental plates gives the underlying mantle more time to erode the continent’s base, ultimately leading to volcanic activity.
    • This is similar to placing paper under a candle. When the paper is moved swiftly over the candle, it may turn black but is unlikely to burn as a whole. 
    • But if the paper moves slowly over the flame, there is enough time to burn the paper completely.
• Significance of volcanic eruptions:
  • Previous studies have linked major volcanic eruptions with past mass extinctions and disturbances in the global climatic, environmental and the carbon cycle.
  • Large igneous province volcanism, formations due to major volcanic eruptions occurring throughout Earth’s history, released large quantities of greenhouse gasses and toxic compounds into the atmosphere.
  • The sea warmed up by 4°C to 10°C, even at low- to mid-latitudes. 
  • Increased acidic levels and a lack of oxygen drove major ocean extinctions.

More about Volcanism

• Volcano:
  • A volcano is a feature in Earth’s crust where molten rock is squeezed out onto the Earth’s surface. 
    • Magma is an extremely hot liquid and semi-liquid rock located under Earth’s surface. 
    • When magma flows onto Earth’s surface, it is called lava.
  • Along with lava, volcanoes also release gases, ash, and solid rock.
    • Volcanic mountains:
      • When the lava cools and hardens, it forms into the cone-shaped mountain we think of as a volcano. 
• Volcanism and movement of tectonic plates:
  • Most of the world’s volcanoes are found around the edges of tectonic plates, both on land and in the oceans.
    • Volcanoes occur along both convergent (subduction) and divergent (rift) boundaries but are generally absent along strike-slip plate margins. 
  • Difference between convergent (subduction) and divergent (rift) volcanoes:
    • Most subduction-related volcanoes are explosive and build stratovolcanoes, while rift volcanoes tend to be more effusive and build shield volcanoes, though there are exceptions to both these generalities. 
    • Subduction-related volcanoes erupt basalt, andesite, dacite, and rhyolite, andesite being the predominant rock type. 
    • Rift-related volcanoes, especially on the ocean floor, erupt mainly basalt.
• Geographical spread of volcanoes:
  • Subduction volcanoes:
    • The volcanoes on the western and northern margin of the Pacific Plate (New Zealand, New Guinea, Mariana Islands, Japan, Kamchatka, and the Aleutian Islands) are all subduction volcanoes. 
  • Rift volcanoes:
    • The rift volcanoes are largely hidden along the submarine crest of the East Pacific Rise and the Pacific-Antarctic Ridge.
  • Pacific ring of fire:
    • The Ring of Fire is a string of volcanoes and sites of seismic activity, or earthquakes, around the edges of the Pacific Ocean. 
    • Roughly 90% of all earthquakes occur along the Ring of Fire, and the ring is dotted with 75% of all active volcanoes on Earth.

Source: DTE