Week Three Topic: Earth Subsystems and Earth Materials

The Geosphere

  • Portion of the Earth that includes the interior structure, rocks and minerals, landforms, and all physical processes on land that shapes Earth’s surface.

Determining the Properties of the Earth

  • Two Types of Waves Travelling through Earth:
  • P-waves – which travel fast through both solids and liquids.
  • S-waves – travel slower than P-waves and can travel only through solids.

Crust

  • 5 to 70 km thick layer
  • Oxygen, Silicon, Aluminum, Iron, Calcium, Sodium, Potassium and Magnesium.

Mohorovicic Discontinuity

  • Discovered by Croatian seismologist Andrija Mohorovicic.
  • The Moho is now recognized as the transitional boundary that divides the crust and the mantle.

Mantle

  • The extreme temperature and pressure in the asthenosphere cause the rocks to become ductile and thus move like liquid.
  • Made up of silicate rocks.
  • Thickest layer of earth.
  • 84% volume of Earth

Gutenberg Discontinuity

  • Discovered by Beno Gutenberg
  • Serves as a transitional boundary between the lower mantle and the outer core.

Core

  • MADE UP OF IRON AND NICKEL.
  • IRON IS PARTICULARLY IMPORTANT BECAUSE THIS IS THE PRIMARY SOURCE OF EARTH’S MAGNETIC FIELD.

Lehmann Discontinuity

  • DISCOVERED BY DANISH SEISMOLOGIST INGE LEHMANN, STUDIED THE SHOCK WAVES AND REALIZED THAT THESE WAVES HAD TRAVELED SOME DISTANCE INTO THE CORE AND THEN BOUNCED OFF TO SOME KIND OF BOUNDARY.
  • TRANSITIONAL BOUNDARY BETWEEN THE INNER CORE AND THE OUTER CORE.

The importance of Water

  • WATER COULD BE IN LIQUID FORM, NOT JUST SOLID AND GAS.
  • WATER HAS A NEUTRAL PH.
  • WATER IS A GOOD CONDUCTOR OF HEAT AND ENERGY.
  • WATER HAS A HIGH SPECIFIC HEAT.
  • WATER IS A UNIVERSAL SOLVENT.

Two Groups of Water

  • SURFACE WATER
  • MARINE WATER – HIGHER SALT CONTENT FOUND IN LARGER BODIES OF WATER SUCH AS OCEANS, SEAS, BAYS, AND GULF.
  • FRESHWATER – ARE THOSE IN LAKES, RIVERS, SPRINGS, AND FALLS, WITH LOWER SALT CONTENT.
  • GROUNDWATER
  • AQUIFER – UNDERGROUND LAYER OF WATER-BEARING ROCKS. ACTS AS A RESERVOIR FOR GROUNDWATER AND MAY CONTAIN LARGE AMOUNTS OF MINERALS SUCH AS MAGNESIUM, CALCIUM, ETC.

Minerals

  • ARE NATURALLY OCCURRING INORGANIC SOLIDS.
  • HAVE CRYSTALLINE STRUCTURES (THE ATOMS OF WHICH ARE ARRANGED IN AN ORDERLY REPEATING PATTERN) AND DEFINITE COMPOSITION (THE ELEMENTS OF WHICH HAVE SPECIFIC PROPORTIONS.

Physical Properties of Minerals

Color

  • USUALLY THE PROPERTY USED TO IDENTIFY MINERALS EASILY. IT IS A RESULT OF THE WAY MINERALS ABSORB LIGHT. LEAST RELIABLE IN IDENTIFYING MINERALS.

Streak

  • THE COLOR OF MINERAL IN POWDER FORM.
  • SCIENTISTS CAN PULVERIZE THEM TO GET THEIR TRUE COLOR.
  • BUT MINERAL LOSES THEIR INTEGRITY.

Hardness

  • REFERS TO THE MEASURE OF THE MINERAL’S RESISTANCE TO SCRATCHING.
  • THE MOH’S SCALE OF HARDNESS WAS DEVELOPED IN 1812 BY FREDERICK MOHS.
MINERAL COMMON OBJECTS
1 TALC POWDER
2 GYPSUM FINGERNAIL
3 CALCITE TOOTH
4 FLUORITE IRON NAIL
5 APATITE WINDOW GLASS
6 ORTHOCLASE FELDSPAR STEEL FILE
7 QUARTZ PORCELAIN
8 TOPAZ MOH’S RELATIVE HARDNESS
9 CORUNDUM SAPPHIRE, RUBY
10 DIAMOND NONE

Cleavage and Fracture

  • USED TO DESCRIBE HOW MINERALS BREAK INTO PIECES.
  • THE BREAKAGE ALONG THE CRYSTALLINE STRUCTURE WHERE A MINERAL IS LIKELY TO BREAK SMOOTHLY IS KNOWN AS CLEAVAGE.
  • A MINERAL FRACTURES WHEN IT BREAKS IN A DIRECTION WHERE THERE IS NO CLEAVAGE.

Crystalline Structure

  • OR THE CRYSTAL LATTICE, TELLS HOW A MINERAL’S CRYSTALS ARE ARRANGED.
  • CRYSTAL SOLID IS SAID TO FORM A REGULAR REPEATING THREE-DIMENSIONAL CRYSTAL LATTICE, WHILE AN AMORPHOUS SOLID FORMS AGGREGATES THAT HAVE NO PATRICULAR ORDER OR ARRANGEMENT.

Transparency or Diapheneity

  • INDICATES THE EXTENT OF LIGHT THAT CAN PASS THROUGH THE MINERAL.

Magnetism

  • INDICATES THE ABILITY OF A MINERAL TO ATTRACT OR REPEL OTHER MINERALS.

Tenacity

  • THE LEVEL OF RESISTANCE OR REACTION OF MINERALS TO STRESS SUCH AS CRUSHING, BENDING, BREAKING, OR LEAVING. IT CAN TELL IF A MINERAL IS BRITTLE, MALLEABLE, ELASTIC.

Luster

  • REFERS TO THE REACTION OF A MINERAL TO LIGHT. IT DETERMINES HOW BRILLIANT OR DULL THE MINERAL IS.

Odor

  • THE DISTINCT SMELL OF A MINERAL THAT IS USUALLY RELEASED FROM A CHEMICAL REACTION WHEN SUBJECTED TO WATER, HEAT OR AIR OR FRICTION.

Specific Gravity

  • A MEASURE OF THE DENSITY OF A MINERAL. IT DETERMINES HOW HEAVY THE MINERAL IS BY ITS WEIGHT TO WATER.

 

Chemical Properties of Minerals

  • Silicate Class
    • THE LARGEST AND MOST ABUNDANT GROUP CONTAINING SILICON AND OXYGEN WITH SOME ALUMINUM, MAGNESIUM, IRON AND CALCIUM.
  • Carbonate Class
    • THE MOSTLY FOUND DEPOSITED IN MARINE ENVIRONMENTS. MINERALS BELONGING TO THIS GROUP ARE FORMED FROM THE SHELLS OF DEAD PLANKTON AND OTHER MARINE ORGANISMS.
  • Sulphate Class
    • FORMS IN AREAS WITH HIGH EVAPORATION RATES AND WHERE SALTY WATERS SLOWLY EVAPORATE. DURING THIS PROCESS, THE FORMATION OF SULPHATES AND HALIDES IN WATER-SEDIMENT INTERFACE OCCURS.
  • Halide Class
    • CONTAINS NATURAL SALTS AND INCLUDES FLUORITE, HALITE, SYLVITE, AND SAL AMMONIAC COMPONENTS. THESE MINERALS USUALLY FORM IN LAKES, PONDS, AND OTHER LANDLOCKED SEAS SUCH AS THE DEAD SEA AND THE GREAT SALT LAKE. MINERALS IN THIS CLASS HAVE RELATIVELY LOW HARDNESS, MAY BE TRANSPARENT, HAVE GOOD CLEAVAGE, HAVE LOW SPECIFIC GRAVITIES, AND ARE POOR CONDUCTORS OF HEAT AND ELECTRICITY.
  • Oxide Class
    • METALLIC MINERALS SUCH AS HEMATITE AND GEMSTONES SUCH AS CHRYSOBERYL AND SPINEL BELONG TO THIS CLASS. IN SCIENCE, THESE MINERALS ARE IMPORTANT AS THEY CARRY HISTORIES OF CHANGES IN EARTH’S MAGNETIC FIELD. THEY ARE FORMED AS PRECIPITATES CLOSE TO EARTH’S SURFACE OR AS OXIDATION PRODUCTS OF MINERALS DURING THE PROCESS OF WEATHERING.
  • Sulphide Class
    • HAS IMPORTANT METALS SUCH AS COPPER, LEAD, AND SILVER, WHICH ARE CONSIDERED ECONOMICALLY SIGNIFICANT. THESE METALS ARE FOUND IN ELECTRICAL WIRES, INDUSTRIAL MATERIALS, AND OTHER THINGS THAT ARE NEEDED IN CONSTRUCTION.
  • Phosphate Class
    • CONTAINS MINERALS WITH PHOSPHORUS. THE PHOSPHATE CLASS IS CONSIDERED AN IMPORTANT BIOLOGICAL MINERAL FOUND IN THE TEETH AND BONES OF MANY ANIMALS.
  • Native Element Class
    • CONTAINS METALS AND INTERMETALLIC ELEMENTS, SEMI METALS, NONMETALS, OR NATURAL ALLOYS AND CONSTITUENTS OF A FEW RARE METEORITES.

 

Rocks

  • NATURAL SUBSTANCES CONSISTING OF AGGREGATE MINERALS CLUMPED TOGETHER WITH OTHER EARTH MATERIALS THROUGH NATURAL PROCESSES.

Classification of Rocks

  • IGNEOUS ROCKS – ARE CRYSTALLIZED FROM MAGMA OR MOLTEN OR PARTIALLY MOLTEN VOLCANIC MATERIALS THAT CAME FROM WITHIN EARTH.
  • SEDIMENTARY ROCKS – ROCKS THAT HAVE FORMED FROM THE DEPOSITION OF DIFFERENT MATERIALS ON EARTH’S SURFACE. THEY COME FROM PRE EXISTING ROCKS OR PIECES OF DEAD ORGANISMS THAT HAVE BEEN LITHIFIED OR CEMENTED TOGETHER BY NATURAL PROCESSES.
  • METAMORPHIC ROCKS – ROCKS THAT DERIVE FROM IGNEOUS OR SEDIMENTARY ROCKS THAT WERE EXPOSED TO HIGH PRESSURE, HIGH TEMPERATURE, OR A COMBINATION OF BOTH, DEEP BELOW THE SURFACE OF EARTH.

 

To read the whole topic: Download the lecture notes in pdf format. Click on the word “Download Me” below.

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