EVIDENCES

• Evidences:

  • Jigsaw Puzzle
  • Fossils
  • Distribution of Fossils
  • Rocks of same age across the ocean
  • Tillite Deposits
  • Placer Deposits
  • Age of Seafloor
  • Records of Magnetic Reversals
  • Convection Current
  • GPS (Global Positioning System)
• Jigsaw Puzzle


  It seems very impossible that the seven continents, which are currently thousands of miles away from each other were actually connected pieces of a supercontinent. The most visible and fascinating evidence that these continents were once one is their shapes.
• One piece of evidence for plate movement based on the shapes of continents?

  • Continents like Africa and South America fit together
  • India, Antarctica, and Australia match each other
  • Eurasia and North America complete the northern fit
• Fossils


  Are preserved remains or traces of organisms (plants and animals) from the remote past. Fossilized leaves of an extinct plant Glossopteris were found in 250 million years old rocks. These fossils were located in the continents of Southern Africa, Australia, India, and Antarctica, which are now separated from each other by wide oceans.
• Why is it unlikely that Glossopteris seeds traveled long distances?

  Because the large seeds could not survive a rough ride through ocean waves.
• Distribution of Fossils


  Mesosaurus and Lystosaurus are freshwater reptiles. Fossils of these animals were discovered in different continents, such as in South America and Africa. The two localities presently 4,800 km apart with an ocean in between them. It is impossible for these reptiles to swim over the vast oceans and move from one continent to another.
• Rocks of Same age across the ocean

  The rocks themselves also provide evidence that continents drifted apart from each other. Rock formations in Africa line up with that in South America as if it were a long mountain range. How come these rock layers in different continents line up together with layers that exactly matched? The folded cape mountains of South America and Africa line up perfectly as if they were once a long mountain range.
• Tillite Deposits 


  Are sedimentary rock made from glacier deposits. The Gondwana system of sediments from India is recognized as having its counterparts in 6 different landmasses in the Southern Hemisphere. Counterparts of this series are found in Madagascar, Africa, Antarctica, Falkland islands, Australia, and India.
• The glacial tillite gives clear evidence for paleoclimates and the drifting of continents.
• Placer Deposits


  The presence of abundant placer deposits of gold along the Ghana coast and the complete lack of its source rocks in the area is a phenomenal fact. The gold-bearing veins are present in Brazil and it is evident that the gold deposits of Ghana in Africa are obtained from the Brazil plateau from the time when the two continents were beside each other.
• The widespread distribution of Permo-Carboniferous glacial sediments in South America, Africa, Madagascar, Arabia, India, Antarctica and Australia was one of the major pieces of evidence for the theory of continental drift. The continuity of glaciers, inferred from oriented glacial striations and deposits called tillites, suggested the existence of the supercontinent of Gondwana, which became a central element of the concept of continental drift.
• Age of Seafloor

  Scientists can determine the age of the seafloor by examining the changing magnetic field of our planet. Every once in a while, the currents in the liquid core, which create the Earth’s magnetic field, reverse themselves: it is called a geomagnetic reversal. This has happened many times throughout Earth's history.
• When scientists studied the magnetic properties of the seafloor, they discovered normal and reversed magnetic stripes with different widths. These magnetic patterns are parallel to the mid-ocean ridges and symmetrical on both sides. As rocks crystallise from lava at the ridges, they literally record the magnetic field of the Earth at the time of their creation.
• These stripes of normal and reverse magnetic fields with different sizes can be matched with the geomagnetic reversals records obtained from continental rocks already dated. New oceanic crust forms continuously at the mid-ocean ridges. While it cools down, it records the magnetic field during its formation. The two parts of the oceanic plate are pulled apart, and magnetic stripes become older as they move away from the mid-ocean ridge.
• To confirm the ages obtained with magnetic records, and get an absolute age of the seafloor, scientists use the radioactive dating technique. When the lava solidifies at the ridges to form the new seafloor, radioactive elements coming from the mantle are trapped in it. By measuring the amount of remaining radioactive elements and daughter products in the seafloor, scientists can determine when the magma crystallized, and thus know the absolute age of the seafloor.
• Records of Magnetic Reversals 


  Happened many times in the past. Its occurrence can be explained through the magnetic patterns in magnetic rocks, especially those found in the ocean floor. When lava solidifies, iron bearing minerals crystallize. As these crystallize, the minerals behave like tiny compasses and align with the Earth’s magnetic field. So, when magnetic reversal occurs, there is also a change in the polarity of the rocks.
• Convection Currents 


  Provide one potential driving force for plate movement. The plastic movement of the mantle material moves like the flow of mountain glaciers, carrying the lithospheric plates along as the convection movement in the mantle moves the asthenosphere. Slab pull, slab (trench) suction and ridge push may also contribute to plate movement. Slab pull and slab suction mean that the mass of the descending plate pulls the trailing lithospheric slab across the asthenosphere and into the subduction zone.
• Global Positioning System (GPS)


  Geodesy, the science of measuring the Earth's shape and positions on it, allows the measurement of plate motion directly. This network is more stable than the Earth's surface, so when a whole continent moves somewhere at a few centimeters per year, it can tell. It can show that tectonic movements within plates.
• • Jigsaw Puzzlelike continents
  • Rock Layers
  • Glacial Track
  • Paleomagnetism
  • Glossopteris
  • Mesosaurus and Lystosaurus
  • Coal Deposits
  • Hotspot Tracks
  • Geological Structures
  • GPS (Global Positioning System)
• The presence of identical rock types and ages on separated continents indicates the past movements and collisions of tectonic plates.
• What do glacial tracks found in warm areas suggest?

  These regions were once close to the poles
• Paleomagnetism 


  The orientation of minerals in new rocks created on mid-ocean ridges aligns with the Earth's magnetic fields
• What do reversals in Earth's magnetic fields indicate in rocks?

  They are recorded in the rocks with reversed polarity
• What do coal deposits found in various regions indicate about past climates?

  These regions must have been closer to the equator in the past
• hotspots


  Locations on Earth's surface that have experienced volcanic activity due to stationary mantle plumes.
• How do mantle plumes relate to plate movement?

  They remain stationary while the plates move above them, causing volcanic activity.
• What does the Hawaiian-Emperor seamount chain indicate about plate movement?

  The abrupt change in orientation reflects a change in the direction of plate movement.
• What geologic structures indicate plate movement?

  • Mountain ranges
  • Ridges
  • Volcanoes
  • Trenches
• What is the role of GPS data in studying plate movement?

  It tracks the positions of tectonic plates and helps predict earthquakes and volcanic activity
• How do GPS stations contribute to understanding tectonic plate interactions?

  They continuously record their positions to identify the direction and rate of movement.