EARTH SCIENCE

• Liquid nature of the outer core

  Attributed to extremely high temperatures (more than 3000°C!) that melt Fe, Ni, and all other elements
• Flow of liquid metals in the outer core

  Responsible for the Earth's magnetic field
• Outer core


  Terminates at a depth of 5,150 km, where the solid inner core begins
• Outer-inner core boundary


  Also known as the Lehmann discontinuity
• Inner core


  Despite the extreme temperature, the overwhelming pressure forces it to be a solid ball of mostly Fe
• Temperatures in the inner core


  Similar to the temperatures of the surface of the Sun—around more than 5400°C
• Minerals are building blocks of rocks
• To be considered a mineral, it must be

  Naturally-occurring<|>Inorganic<|>Homogeneous solid<|>Have definite chemical composition<|>Have ordered crystalline structure
• Man-made materials such as synthetic diamonds cannot be considered real minerals
• Organic materials such as pearls or sugar are not minerals
• Water is not a mineral, whereas ice is considered a mineral
• Mercury occurs as a liquid in its natural state and is regarded as a mineraloid
• Color


  Refers to the wavelengths of light reflected by the minerals
• Luster


  Describes how light is reflected from the mineral's surface
• Metallic luster


  Brilliantly cut gems are described to have an adamantine luster
• Crystal Habit or Shape


  Refers to the shape of each crystal or an aggregate of crystals
• Streak


  The color of the mineral when it is powdered
• Hardness


  Refers to how resistant a mineral is to scratching, described using the Mohs' Hardness Scale
• Cleavage


  The tendency of a mineral to break along preferred planes called zones of weakness
• Fracture


  Produced if a mineral doesn't break along zones of weakness
• Density or Specific Gravity


  Ratio between a mineral's weight and the weight of a specific volume of water
• Tenacity


  • Brittle
  • Elastic
  • Flexible
  • Malleable
  • Ductile
  • Sectile
• Diaphaneity


  Refers to how well light travels through a mineral
• Transparent minerals


  Allow almost all light to travel through
• Translucent minerals


  Only allow some light to travel and exit the mineral, giving off a cloudy or murky appearance
• Opaque minerals


  Do not allow light to travel through
• Magnetism


  Describes the magnetic property of a mineral
• Magnetite


  An example of a strongly magnetic mineral
• Effervescence


  Describes a mineral's reaction to a strong acid such as HCl (hydrochloric acid)
• Highly effervescent minerals


  Exhibit intense "fizzing" or "bubbling" when exposed to HCl
• Weakly effervescent minerals


  Only show light "fizzing" when exposed to HCl
• Odor and Taste


  Used by geologists to identify minerals
• Thousands of different minerals have been identified and named, and the list grows every year
• Only a few of these minerals are abundant on the Earth's crust, called rock-forming minerals
• Out of all the elements, only 8 make up most rock-forming minerals
• Silicates


  The most common mineral group, uses oxygen and silicon as their "building blocks"
• Non-silicate mineral groups


  • Native elements
  • Carbonates
  • Oxides
  • Sulfates
  • Phosphates
  • Others
• Rocks are naturally-occurring aggregates of minerals and mineraloids
• Igneous rocks


  Formed when molten material cools and solidifies
• Intrusive igneous rocks


  Form below the surface of the Earth