Earths Structure and Motion Chapter 4

Chapter 4.1 – Earth’s Formation

Geology The study of the planet Earth, its structure and composition and how it has changed over time

Origin of the Solar System

Nebular Hypothesis Image (a) 4.6 Billion years ago a cloud of dust and gas was rotating slowly Cloud was at least 10 billion kilometers in diameter

Image (b) The cloud shrank under the pull of its own gravity As it shrank the rotation increased Material in the rotating cloud gathered around its center

Image (c) The compression of material made its interior VERY HOT Caused hydrogen fusion to occur A star was born  the SUN

Image (d) A platelike disc formed around the sun It began to condense, forming solid particles of ice and rock Eventually combined into larger bodies call planetesimals.

Image (e) Planetesimals continued to compress and spin, while colliding with other objects Eventually became planets and moons

Summarize in your own words the Nebular Hypothesis

Earth’s Location The third closest planetesimal to the sun became Earth

Earth’s Size and Shape Earth is not a perfect sphere It bulges in the center = oblate spheroid

Earth’s Size Total surface area = 510 million square kilometers 29% = Dry Land 71% = Covered by water

Earth’s Interior Multiple impacts caused early Earth to heat up Heavy elements such as Iron & Nickel melted Separated into layers – denser materials located in the center

Inner Core – Solid iron and nickel

Inner Core – Solid iron and nickel Outer Core – Liquid iron and nickel

Inner Core – Solid iron and nickel Outer Core – Liquid iron and nickel Mantle – Thickest layer, solid & some liquid, iron, silicon, and magnesium.

Inner Core – Solid iron and nickel Outer Core – Liquid iron and nickel Mantle – Thickest layer, solid & some liquid, iron, silicon, and magnesium. Crust – rigid layer of rocks – Earths surface

Lithosphere: the crust and uppermost portion of the mantle Asthenosphere: thin slushlike layer of the mantle Lithosphere floats on top of the Asthenosphere

EARTH’S HEAT Generated from meteorite impacts and compression Decay of radioactive isotopes Elements that release heat as they disintegrate into more stable forms

Earth’s Heat Since its original heating, Earth has been slowly losing heat Amount of heat loss varies from place to place Some rocks lose heat more quickly than others The thickness of the crustal rock varies from place to place The percentage of radioactive materials in rocks varies

Underground caves maintain constant temperature all year Below 70 meters ground temperatures begin to heat up ~ 1oC for every 40 meters in depth

Describe three sources of Earth’s internal heat Describe three sources of Earth’s internal heat. Which internal process is still producing heat?

Earth’s Magnetic Field Magnetic north is different from geographic north Magnetic north is 11o away from the poles.

Earth’s Magnetic Field Scientist hypothesize that the magnetic field is the result of the movement of fluid in the outer core An electric current is generated when liquid iron moves across an already existing magnetic field. These two fields create Earth’s strong magnetic field

4.2 Earth’s Rotation

Earth’s Rotation Rotation: the spinning of Earth around it axis Earth completes one full rotation every 24 hours

Evidence for Rotation Foucault Pendulum Built pendulum 20 stories high Once a pendulum is in motion, its direction of swing will not change

Foucault's Pendulum Shifted 11o each hour in a clockwise direction After 8 hours it was swinging at a right angle to its starting direction

Foucault's Pendulum Shifted 11o each hour in a clockwise direction After 8 hours it was swinging at a right angle to its starting direction The pendulum could not have changed its direction of swing, therefore the Earth was turning beneath it

More Evidence of Earth’s Rotation If Earth did not rotate, winds would blow along straight paths from areas of high pressure to areas of low pressure.

Wind: Northern Hemisphere – deflected to the right Southern Hemisphere – deflected to the left

Axis and Rate of Rotation Earth rotates as it travels around the sun Earth’s axis of rotation is an imaginary straight line from the North to South pole

Axis and Rate of Rotation Earth’s axis is not perpendicular to its orbital plane It is tilted 23.5o

The axis points towards Polaris, the North Star

Earth rotates 360o every 24 hours Speed of rotation varies from point to point Equator = 1690 kilometers/hour Northern USA = ~ 1300 kilometers/hour Poles = almost 0 kilometers/hour

Effects of Rotation Only half of Earth receives sunlight at any given time If Earth did not rotate, the half facing the Sun would have constant light, while the other half would be dark

Measuring Time For centuries, people figured the time of day by the Sun’s position in the sky

Measuring Time For centuries, people figured the time of day by the Sun’s position in the sky Sun rises on the eastern horizon, moves across the sky, and sets below the western horizon

Measuring Time For centuries, people figured the time of day by the Sun’s position in the sky Sun rises on the eastern horizon, moves across the sky, and sets below the western horizon Solar noon occurs when the sun is at the highest point on this arc

Measuring Time Solar noon does not occur at the same time everywhere. Moves westward at a rate of 15o each hour or 1o every four minutes. Led to the creation of Time Zones

Standard Time Zones There are 24 worldwide time zones, each 15o of longitude wide Division lines are called time meridians

International Date Line The 180o longitude - where the date changes

4.3 Earth’s Revolution

Earth’s Revolution Revolution: the movement of earth in its orbit around the sun

Evidence of Revolution Constellations (groups of stars) are visible on every clear night Their position in the sky appears to change as Earth rotates and revolves

Evidence for Revolution Parallax: As Earth moves in its orbit nearby stars appear to shift in position.

Evidence for Revolution The stars are not actually moving Instead Earth is actually changing positions

Path and Rate of Revolution The direction of Earth’s Revolution and Rotation are the same = Counterclockwise

Earth’s orbit is an ellipse Perihelion – near the sun occurs around January 2 Aphelion – away from the sun occurs around July 4

Effects of Revolution and Tilt Creates the seasons & variations in the length of days and nights Hemisphere tilted towards the sun receives more direct sunlight = summer Hemisphere tilted away from the sun receives less direct sunlight = winter

Summer Solstice Northern Hemisphere is at its maximum tilt towards the sun Longest day of the year First day of summer, ~ June 21

Tropic of Cancer 23.5o N = direct sunlight Arctic Circle 66.5o N= 24 hours of daylight Antarctic Circle 66.5o S= 24 hours of darkness

Winter Solstice Northern Hemisphere is at its maximum tilt away from the sun Shortest day of the year First day of winter, ~ December 21

Equinox Midway between the two solstices Neither hemisphere tilts towards the sun Daytime and nighttime are equal all over the world

Vernal Equinox = ~ March 21 Autumnal Equinox = ~ September 22