Earths Structure and Motion

1
Earths Structure and Motion

• Chapter 4

2
EARTHS FORMATION

• ORIGIN OF THE SOLAR SYSTEM
• NEBULAR HYPOTHESIS
• 4.6 BILLION YEARS AGO A GREAT CLOUD OF GAS AND
  DUST ROTATED SLOWLY IN SPACE
  
• THE CLOUD SHRANK
• RATE OF ROTATION INCREASED
• 90 OF THE CLOUD MASS TURNED INTO THE SUN
• 10 OF THE MATERIAL FORMED THE 8 (9?) PLANETS

3
3RD ROCK FROM THE SUN

• THE EARTH
• SHAPE OBLATE SPHERIOD
• BULGING AT THE CENTER AND FLATTENED AT THE POLES
• PROVED BY MEASURING THE WEIGHT OF AN OBJECT AT
  SEVERAL PLACES ON THE EARTH
  
• THE OBJECT WEIGHS MORE AT THE POLES BECAUSE IT IS
  CLOSER TO THE CENTER OF THE EARTH
  
• THE CLOSER TO THE CENTER OF THE EARTH THE
  STRONGER THE PULL OF GRAVITY

4
THE EARTH

• TOTAL SURFACE AREA OF THE EARTH 510 MILLION SQ.
  KILOMETERS
  
• 149 MILLION SQ. KM ARE ABOVE SEA LEVEL
• OCEANS COVER THE REMAINING 361 MILLION SQ KM
• 71 COVERED BY WATER
• 29 LAND ABOVE WATER

5
EARTHS INTERIOR
6
CRUST OF THE EARTH

• LITHOSPHERE THE CRUST AND THE UPPER MOST PART OF
  THE MANTLE
  
• THIS LAYER IS VERY RIGID
• ASTHENOSPHERE THE PART OF THE MANTLE DIRECTLY
  UNDER THE LITHOSPHERE
  
• THIS LAYER IS A SLUSHY ROCKY MATERIAL

7
EARTHS HEAT

• WHERE DOES THE HEAT COME FROM?
• METEORITE IMPACTS
• COMPRESSION OF THE EARTHS MATERIALS
• DECAY OF RADIOACTIVE ISOTOPES ELEMENTS THAT
  RELEASE HEAT AS THEY DISINTEGRATE

8
EARTHS HEAT

• THE EARTH HAS SLOWLY BEEN LOSING HEAT
• LOSS OF HEAT VARIES FROM PLACE TO PLACE BECAUSE
  OF
  
• ROCKS LOSE HEAT AT DIFFERENT RATES
• THICKNESS OF THE EARTHS CRUST VARIES FROM PLACE
  TO PLACE
  
• OF RADIOACTIVE MATERIALS VARIES IN ROCKS

9
WHY ARE CAVES COOL?

• IF THE EARTH IS SO HOT, HOW DO CAVES STAY COOL?
• DEEP CAVES STAY COOL ALL YEAR
• NEITHER THE SUNS HEAT OR THE WINTERS COLD CAN
  PENETRATE THAT FAR BELOW THE SURFACE
  
• THE CRUST IS COOL TO ABOUT A DEPTH OF 70 METERS

10
EARTHS HEAT

• BELOW A DEPTH OF 70 METERS THE EARTHS CRUST
  STARTS TO HEAT UP
  
• RATE OF INCREASE 10 C FOR EVERY 40 METERS OF
  DEPTH
  
• UNTIL THE 1000 METER MARK THEN THE INCREASE IS
  MORE GRADUAL

11
MAGNETIC FIELD THEORY

• AN ELECTRIC CURRENT IS GENERATED WHEN THE LIQUID
  IRON MOVES ACROSS A WEAK BUT ALREADY EXISTING
  MAGNETIC FIELD
  
• THE ELECTRIC CURRENT PRODUCES A MAGNETIC FIELD
  AND WITH THE FLUID MOTION PRODUCES ANOTHER
  MAGNETIC FIELD
  
• TOGETHER THESE FIELDS CREATE EARTHS STRONG
  MAGNETIC FIELD

12
MAGNETIC FIELD

• COMPASS POINTS TO THE EARTHS MAGNETIC NORTH POLE
  NOT THE GEOGRAPHIC NORTH POLE
  
• THE MAGNETIC NORTH POLE IS 11 DEGREES AWAY FROM
  THE GEOGRAPHIC NORTH POLE
  
• EVERY SO OFTEN THE EARTHS MAGNETIC POLES CHANGE

13
EARTHS ROTATION

• THE EARTH ROTATES ON ITS AXIS ONCE EVERY 24
  HOURS
  
• DISCOVERED IN 1851 BY JEAN FOUCAULT USING A
  PENDULUM 20 STORIES HIGH
  
• MORE EVIDENCE IS SEEN BY WIND PATTERNS AROUND THE
  EARTH

14
EARTH ROTATES

• EARTH IS TILTED 23.50 FROM THE SUN
• THIS CAUSES THE SEASONS AS THE EARTH REVOLVES
  AROUND THE SUN
  
• EARTH ROTATES 3600 EVERY 24 HOURS WHICH IS 150
  EVERY HOUR
  
• THE EARTH ROTATES FASTER AT THE EQUATOR THAN AT
  THE POLES

15
EARTH ROTATES

• LOOKING DOWN FROM SPACE AT THE NORTH POLE THE
  EARTH ROTATES COUNTERCLOCKWISE
  
• SPEED OF ROTATION AT THE EQUATOR IS 1690
  KM/HOUR
  
• SPEED OF ROTATION AT THE POLES 0 KM/HOUR

16
TIME ZONES

• 24 WORLD WIDE STANDARD TIME ZONES
• EACH 150 OF LONGITUDE WIDE
• THE BASIS FOR TIME ZONES IS THE RATE AT WHICH THE
  SUN APPEARS TO MOVE ACROSS THE SKY
  
• EACH TIME ZONE IS CENTERED ON A LINE OF LONGITUDE
  CALLED A TIME MERIDIAN

17
TIME ZONES

• THE STARTING POINT FOR TIME ZONES IS THE PRIME
  MERIDIAN
  
• BECAUSE OF POLITICS THE LINES OF STANDARD TIME
  ZONES ARE NOT STRAIGHT
  
• INTERNATIONAL DATE LINE IS THE IMAGINARY LINE
  WHERE THE DATE CHANGES
  
• THE INTERNATION DATE LINE LIES WITHIN A TIME ZONE
  ITS THE SAME TIME ON EITHER SIDE BUT DIFFERENT
  DAYS!

18
EARTHS REVOLUTION

• THE EARTH REVOLVES AROUND THE SUN ONCE EVERY 365
  DAYS (APX)
  
• EARTHS ORBIT IS AN ELLIPSE
• AVERAGE DISTANCE FROM THE SUN IS 93 MILLION MILES
  OR 150 MILLION KM
  
• THE SUN IS ABOUT 2.4 MILLION KM FROM THE CENTER
  OF THE ORBIT

19
EARTHS REVOLUTION

• AT PERIHELION THE EARTH IS ABOUT 147.6 MILLION
  KM FROM THE SUN
  
• AT APHELION THE EARTH IS ABOUT 152.4 MILLION KM
  FROM THE SUN

20
REASON FOR THE SEASONS

• AS THE EARTH REVOLVES AROUND THE SUN THE TILT OF
  THE EARTH CAUSES THE SUNS RAYS TO HIT THE EARTH
  DIFFERENTLY
  
• SO THE EARTHS SURFACE GETS CHANGING AMOUNTS OF
  SUNLIGHT

21
SEASONS

• THE NORTHERN AND SOUTHERN HEMISPHERES EXPERIENCE
  OPPOSITE SEASONS
  
• SUMMER AND WINTER SOLSTICE
• LONGEST AND SHORTEST DAYS OF THE YEAR
• SPRING AND FALL EQUINOX
• EQUAL DAY AND NIGHT LENGTH