Evidences Of Plate Movement Flashcards
Evidences of Plate Movement
- Direct measurement of the movement of the locations on the Earth’s surface using precise positioning technologies such as the global positioning system (GPS), satellite laser ranging and long baseline.
shows that large areas of the crust move in well-defined patterns and do not deform
internally. It is a technique in which electromagnetic waves are superimposed to deduce
information about particular waves. The measurement of the plate velocities determines the rates and direction of sea floor spreading measured by data gathered from ships that survey the midocean ridge system.
Interferometry
are methods that are based around the idea of measuring distance between two points on earth using some intermediary transmitter in space. Both SLR and VLBI allow repeated measurement of the distance between change
The SLR (Satellite Laser Ranging) and the VLBI (Very Long Baseline Interferometry)
uses two lasers on Earth, each of which fires a laser to a satellite orbiting the planet. The beam is reflected back to each laser and the difference in the laser beam travel time is used to estimate the distance between the two laser on Earth.
SLR (Satellite Laser Ranging)
Another approach using radio-telescopes measuring natural radio signals from deep space
achieves a similar effect. Using the measurement, scientists can accurately estimate the movement of tectonic plates.
VLBI (Very Long Baseline Interferometry)
Scientists use a system of satellites to measure the rate of tectonic plate movement.
Tectonic plate movements are so slow and gradual that you can’t see or feel them.
These are measured in centimeters per year.
Global Positioning System (GPS)
Evidences of Plate Movement
The long faults offsetting the mid-ocean ridge system support the movement of the oceanic crust.
- Faulted nature of the ocean floor
Evidences of Plate Movement
The shapes of the many continents such that they look like pieces of a jigsaw puzzle. For example: the margins of North and South America fit into the shapes of the west coast of Africa and Europe.
- Jigsaw fit of many continental margins
Evidences of Plate Movement
• There are ridges such as the Mid-Atlantic Ridge where plates separate due to lava welling up between the plates as they pull apart. Likewise, for mountain ranges formed from the plates converge, the motion of the plates may only be centimeters per century and can be measured by laser ranging techniques.
• If the crustal plates are pulling apart at boundaries like the Mid-Atlantic Ridge, the sea floor near these ridges should be very young geologically, since it is formed of material upwelling from the interior. This is indeed the case, as the following figure shows.
- Difference between the average age of sea floors and continents
Evidences of Plate Movement
• The magma that erupts from the mantle in mid-ocean ridges contain atoms of iron. These atoms align themselves to the Earth’s magnetic field so that when the magma solidifies to form new curst, the atoms lock into position. The solid crust flows away from the mid-oceanic ridge in both directions carrying with it the original magnetic orientation. Over time the Earth’s magnetic field reverses so new crust forming along the ridge takes over. A symmetrically striped pattern is created in the ocean floor.
• The gradual process of seafloor spreading slowly pushes tectonic plates apart while generating new rock from cooled magma. Ocean floor rocks close to a mid-ocean ridge are not only younger than distant rocks, they also display consistent bands of magnetism based on their age Every few hundred thousand years the earth’s magnetic field reverses, in a process known as geomagnetic reversal. Some bands of rock were produced during a time when the polarity of the earth’s magnetic field was the reverse of its current polarity.
- Proof of seafloor spreading is found in the magnetism patterns recorded in ocean floor
allows scientists to
study the movement of ocean floors over time.
Geomagnetic reversal
is the study of magnetic field orientation in rock strata. This reinforced the case
for plate tectonic. Iron rich magnetic minerals such as magnetite are present in basaltic lava flows.
A characteristic of ferromagnetism is that it disappears when you heat the material above a
temperature known as Curie temperature which is 1 043 K for the pure iron but is reported to be
about 850 K (580ºC) for the magnetite. When these slightly magnetized in the direction of the
Earth’s magnetic field at this time, this forms a durable record of the direction of the magnetic field
of the earth at the time of solidification.
Paleomagnetism
Evidences of Plate Movement
There is a large amount of seismic, volcanic, and geothermal activity along plate boundaries. This was concluded from the gathered data of epicenters and earthquakes.
- Concentration of earthquakes and volcanoes in narrow interconnected belts
Evidences of Plate Movement
Many fossil comparisons along the edges of continents that look like they fit together suggest species similarities that would only make sense if the two continents were joined at some point in the past.
- Geographic continuity of identical fossil species when continental margins are reconstructed
Evidences of Plate Movement
- Evolution and distribution of species
Biologists have studied that species across different continents support evolution. Species that evolved before the breakup of the supercontinent Pangaea were distributed worldwide while species that evolved after the breakup are more localized.
