Transcript 4.1 Earth`s Formation

EARTH’S, FORMATION
SHAPE, DIMENSIONS AND
HEAT
CHAPTER 4.1
Earth’s Origin
Nebular Hypothesis
Observe an animation showing the origin of the solar system.
Earth’s Size and Shape
HISTORICAL EVIDENCE OF
SHAPE
1.
2.
3.
4.
5.
SHIPS MAST
CHANGING POSITIONS OF
CONSTELLATIONS
EARTHS ARC DURING ECLIPSE
GRAVITATION – OBJECTS WEIGH
NEARLY THE SAME
MAGELLAN’S CIRCUMNAVIGATION
OBLATE SPHEROID – TRUE SHAPE OF EARTH.
SLIGHTLY FLATTENED AT THE POLES (40,007
KM) BULGING AT THE EQUATOR (40,074 KM).
OBJECTS AT THE POLES WEIGH MORE THAN
AT THE EQUATOR!
Eratosthenes
• (276 - 195 B.C.)
ERATOSTHENES – FIRST SCIENTIFIC
MEASUREMENT OF THE CIRCUMFERENCE OF
THE EARTH.
TWO REQUIREMENTS:
– ANGULAR DIFFERENCE FROM SYENE
TO ALEXANDRIA
– SURFACE DISTANCE BETWEEN TWO
CITIES(DIRECTLY NORTH)
Analema


a trace of the annual movement of the
Sun on the sky
Due to the earth's tilt on its axis (23.45°) and its
elliptical orbit around the sun, the relative location
of the sun above the horizon is not constant from
day to day when observed at the same time on
each day. Depending on one's geographical
latitude, this loop will be inclined at different angles
ALTITUDE OF
SUN
HORIZON
Earth is misnamed!
Should be called ocean
(71%) and land (29%)
Earth’s Interior
Layers of Earth
Inner core – solid iron and nickle
Outer core – liquid iron and nickle
Mantle – thickest layer, iron, silicon and
magnesium compounds – behaves as a liquid
Asthenosphere – slush-like layer of mantle
crust floats on
Crust – Thin layer of rigid lighter rock that
includes earth’s surface
Lithosphere – Crust and uppermost part of
mantle
SPECIFIC GRAVITY
Weight of an object compared to the
weight of an equal volume of water.
Useful in mineral identification!
Earth’s avg. density is 5.5
Crust = 2.8
FORMULA
S.G
=
Wa
Wa – WH20
Wa = WEIGHT IN AIR
WH20 = WEIGHT IN WATER
Earth’s Heat
TEMPERATURE
• 70 METERS DEPTH CONSTANT AND
EQUAL TO AVG. YEARLY TEMP OF THAT
LOCATION
•TEMP IN CRUST RISES 10/40 METERS IN
DEPTH
•12,800 KM DIAMETER
•6400 KM RADIUS X 1000 M/KM DIVIDED
BY 40 = 160,000 DEGREES CELSIUS
EARTHQUAKE WAVE STUDIES INDICATE A SOLID
CORE, AND THUS THE MAXIMUM TEMPERATURE
OF THE CORE WOULD BE 70000 C
SOURCES OF INTERNAL HEAT
1. RADIOACTIVITY
2. PRESSURE / COMPRESSION
3. Meteor impacts
Earth’s Magnetic Field
Earth’s Magnetic Field is tilted 11 degrees from
the north pole!