EARTH’S, FORMATION EARTH’S, FORMATION SHAPE, DIMENSIONS SHAPE, DIMENSIONS AND HEATAND HEAT

CHAPTER 4.1CHAPTER 4.1

Earth’s OriginEarth’s Origin

Nebular HypothesisNebular Hypothesis

Observe an animation showing the origin of the solar system.

Earth’s Size and Earth’s Size and ShapeShape

HISTORICAL EVIDENCE OF HISTORICAL EVIDENCE OF SHAPESHAPE

1.1. SHIPS MASTSHIPS MAST

2.2. CHANGING POSITIONS OF CHANGING POSITIONS OF CONSTELLATIONSCONSTELLATIONS

3.3. EARTHS ARC DURING ECLIPSEEARTHS ARC DURING ECLIPSE

4.4. GRAVITATION – OBJECTS WEIGH GRAVITATION – OBJECTS WEIGH NEARLY THE SAMENEARLY THE SAME

5.5. MAGELLAN’S CIRCUMNAVIGATIONMAGELLAN’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!

EratosthenesEratosthenes• (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)

AnalemaAnalema

a trace of the annual movement a trace of the annual movement of the Sun on the sky of the Sun on the sky

Due to the earth's tilt on its axis (23.45°) and Due to the earth's tilt on its axis (23.45°) and its elliptical orbit around the sun, the relative its elliptical orbit around the sun, the relative location of the sun above the horizon is not location of the sun above the horizon is not constant from day to day when observed at constant from day to day when observed at the same time on each day. Depending on the same time on each day. Depending on one's geographical latitude, this loop will be one's geographical latitude, this loop will be inclined at different angles inclined at different angles

HORIZON

ALTITUDE OF

SUN

Earth is misnamed! Should be called ocean (71%) and land (29%)

Earth’s InteriorEarth’s Interior

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

Layers of Earth

SPECIFIC GRAVITYSPECIFIC GRAVITY

Weight of an object compared to Weight of an object compared to the weight of an equal volume of the weight of an equal volume of water. Useful in mineral water. Useful in mineral identification!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 HeatEarth’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 Earth’s Magnetic FieldField

Earth’s Magnetic Field is tilted 11 degrees from the north pole!