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Continental Plates and Volcanism

Posted on September 12, 2022 by admin1  3021

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.

Plate Tectonic Theory/Plate Tectonic

  • Continental Drift Theory was introduced by Alfred Wegener in the yeara 1912 while Theory of Plate Tectonics was independently given by Mckenzie, Parker and Morgan in 1967.
  • According to the theory, Earth has a rigid outer layer, known as the lithosphere, which is typically about 100 km (60 miles) thick and overlies a plastic (moldable, partially molten) layer called the asthenosphere. 
  • The lithosphere is broken up into:
    • seven very large continental- and ocean-sized plates,
    • six or seven medium-sized regional plates, and 
    • several small plates. 
  • These plates move relative to each other.
    • They typically move at rates of 5 to 10 cm (2 to 4 inches) per year, and interact along their boundaries.
    • They converge, diverge, or slip past one another. 
    • Mountain formation:
      • Plate motions cause mountains to rise where plates push together or converge. 
    • Ocean formation:
      • Continents fracture and oceans are formed where plates pull apart or diverge.
  • The continents are embedded in the plates and drift passively with them, which over millions of years results in significant changes in Earth’s geography.
  • Such interactions are thought to be responsible for most of Earth’s seismic and volcanic activity, although earthquakes and volcanoes can occur in plate interiors.
  • Evidence of Plate Tectonic Theory:
  • Continent Puzzle:
    • The continents fit together almost like puzzle pieces forming Pangaea (one super-continent).
  • Fossil evidence:
    • Fossils on different continents are similar to fossils on continents that were once connected.  
    • When the continents split, different life forms developed.
  • Distributions of rocks:
    • Most distributions of rocks within Earth’s crust, including minerals, fossil fuels, and energy resources, are a direct result of the history of plate motions and collisions and the corresponding changes in the configurations of the continents and ocean basins.

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

 
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