Q2L1 CRUST (easy version)

• Crust

  • outermost layer of the geosphere
  • made up mostly of solid rocks and minerals
  • thickness varies from 5 to around 80 km depending where you are on the planet
• Mohorovicic Discontinuity


  boundary between the crust and the mantle
• Tectonic Plates


  broken sections of the lithosphere
• Lithosphere


  made up of the crust, together with the uppermost part of the mantle
• Abundance of Elements on the Crust


  studied using its rocks
• Abundant Elements found on Earth's Crust

  1. Oxygen
  2. Silicon
  3. Aluminum
  4. Iron
• Oxygen


  • most abundant element in Earth's crust
  • serves important roles in industries, medicine, and commercial uses
• Silicon

  • second most common element
  • is found in sand, quartzite, mica, and talc
  • used in producing ceramics, glass, cosmetics, insecticides, and pharmaceuticals
• Aluminum


  • lightweight metal used in making utensil foils and packaging materials
  • also used to manufacture automobile parts, rockets, and machinery
• Iron


  • exists in Earth's crust with a composition of 50 500 ppm
  • it has many applications, one of which is for the production of steel
• Oceanic Crust


  • composed mostly of dark-colored mafic rocks
  • density ranges from 2.9 to 3.1 g/cm³, due to higher iron, magnesium, and calcium content
  • thickness varies from 5 to 18 km
• The oceanic crust is divided into three regions
• Continental Margins


  separate continental from oceanic crust, prominent in passive margins
• Main Parts of Continental Margins

  1. continental shelf
  2. continental slope
  3. continental rise
• Continental Shelf


  a gently sloping, submerged part of the continent
• Continental Slope


  a steeper area where the shelf drops off to deeper oceanic waters
• Continental Rise


  a more gradual incline formed by sediments accumulating at the base of the slope
• Deep Ocean Basins


  lie between continental margins and ocean ridges, featuring seamounts and abyssal plains
• Ocean Ridges


  2 km-high mountain belts of newly formed oceanic crust, occuring in the middle of oceans and wrapping around the globe
• The age of oceanic crust is approximately


  180 million years old
• Continental Crust


  • composed of various rock types, primarily granodiorite
  • can be up to 80 km thick in mountainous areas, with an average thickness of 30 km
  • density ranges from 2.6 to 2.9 g/cm³, lower than oceanic crust
• Continental crust is older than oceanic crust due to continuous recycling due to


  Subduction
• The oldest grain found in the continental crust is about


  4 billion years old
• Features of Continental Crust


  1. mountain belts
  2. cratons
• Mountain Belts


  elevated regions composed of uplifted and deformed rocks, formed through orogeny
• Cratons


  expansive areas with complexly deformed Precambrian crystalline rocks known as shields
• Shields


  covered with a thin layer of sedimentary rocks called stable platforms
• Differentiation Process


  Billions of years ago, Earth was a molten sphere. Upon cooling, lighter materials rose to the surface, forming the crust.
• Conventional Theory


  Earth's crust was formed primarily by volcanic activity.
• Baker and Sofonio's Theory


  Suggested that materials settled onto Earth's surface from the steamy atmosphere.
• Baker and Sofonio


  They proposed a planetoid collision about 4.5 billion years ago, which turned Earth into an ocean of magma. Dissolved minerals from the collision cooled and formed silicate rain that contributed to the crust's formation.
• Three Theories of Crust Formation

  1. Differentiation Process
  2. Conventional Theory
  3. Baker and Sofonio's Theory