Scie Module 1 Lesson 2

• The theory of plate tectonics is a recent explanation describing the processes

  that are taking place at plate boundaries.
• Plate tectonics explains how continents move, why earthquakes occur, and what causes volcanoes to erupt.
• The oldest continental crustal fragment, called the Acasta Gneiss, was dated

  using the Zircon dating technique. This was formed about 4.01 Ba.
• The oldest

  seafloor found at the Mediterranean Sea, on the other hand, was formed about 340

  Ma.
• Plate Tectonic Theory states that the outer rigid layer of Earth (the

  lithosphere) is divided into slabs of rock, called tectonic plates that move across the

  earth's surface relative to each other, like slabs of ice on a lake.
• There are

  movements and different activities taking place at the boundaries such as collision,

  subduction, melting of rocks, or compression of rocks which result to earthquake,

  volcano, and mountain belts formation.
• Rigid moving plates that move towards one another, slide past each other, or

  plates that move apart from one another cause earthquakes and tsunamis.
• Trenches are formed when the denser oceanic lithosphere is subducted by the less

  dense continental lithospheric plate. As these plates grind at the margins,

  earthquakes are produced.
• The subducted oceanic plate is pulled by gravity at the bottom and becomes

  heated as it reaches the mantle where it starts to melt as magma.
• The melted

  magma is now less dense than the surrounding rock and begins to escape to the

  surface of the crust where it forms volcanoes.
• Plates that press against each other

  form mountain folds and later becomes mountain ranges.
• Earthquakes, volcanoes, trenches, mid-ocean ridges, and mountain ranges

  are common geologic features associated with plate boundaries.