Earth’s Size and Shape

Formation of Earth  Most researchers conclude that Earth and the other planets formed at essentially the same time.  Nebular Hypothesis The solar system evolved from an enormous rotating cloud called the solar nebula.

Nebular Hypothesis • The nebula was composed mostly of hydrogen and helium. • About 5 billion years ago, the nebula began to contract. • It assumed a flat, disk shape with the protosun (pre-Sun) at the center. • Inner planets begin to form from metallic and rocky clumps. • Larger outer planets began forming from fragments with a high percentage of ices.

The Nebular Hypothesis C D E B The nebular hypothesis is about how our solar system formed The big bang is how the universe was formed

Layers Form on Earth • As Earth formed, the decay of radioactive elements and heat from high-velocity impacts caused the temperature to increase. • Lighter rocky components floated outward, toward the surface. • Gaseous material escaped from Earth’s interior to produce the primitive atmosphere. http://www.youtube.com/watch?v=WwiiOjyfvAU

Earth’s Shape Kind of like an egg… • VERY CLOSE TO BEING A PERFECT SPHERE • actual shape: OBLATE SPHEROID FLATTENING AT THE POLAR REGIONS SLIGHT BULGE AT THE EQUATOR Kind of like an egg…

Therefore the equatorial diameter is larger… about 43km larger then the polar diameter Polar Diameter: 12,720 Kilometers (7,900 miles) Equatorial diameter is 12,750 kilometers (7,922 mi) 

What evidence is there that we are slightly oblate? Gravity measurements. Gravity is the force of attraction between any 2 objects. Increase mass of objects = increase in gravity Decrease of distances = increase in gravity If Earth were a perfect sphere, it would be expected to exert an equal force on objects at equal distances from the center of earth.

Weight!!! – measure of gravitational force We are further from the center of the Earth at the equator – gravity is less This means we weigh LESS!!! We are closer at the poles… We weigh MORE!!!! The least amount of gravity is farther from the center of Earth The amount is minimal but still evidence for the shape of earth

Why is the earth not perfectly round? Earth’s rotation causes… Bulging at equator Flattening at the poles

Evidence for how we know the earth is round at all and not FLAT 1.) Photographs from outer space 2.) Ships appear to sink gradually below horizon 3.) Spherical shadow cast during an eclipse of the moon 4.) The angle of polaris above the horizon would not change on a flat earth

2.) Ships appear to sink gradually below horizon EVIDENCE that Earth is round and not flat. 1.) PHOTOGRAPHS FROM OUTER SPACE 2.) Ships appear to sink gradually below horizon

EVIDENCE 3.) SPHERICAL SHADOW CAST DURING AN ECLIPSE OF THE MOON

Lunar Eclipse Only a sphere can cast a shadow that appears round. During a lunar eclipse, the earth casts its shadow on the moon during the full moon phase.

EVIDENCE 4.) The angle of Polaris (the north star) above the horizon would not change on a flat Earth. Polaris is the star that lies in space practically over the geographic North Pole of the earth. If you stood at the North Pole, Polaris would be almost directly overhead. Polaris

Why do observations of Polaris help determine the Earth’s shape????? The North Star appears lower and lower in the sky as you travel toward the equator because of earth’s spherical shape. At the North Pole, Polaris appears directly overhead. At the Equator, Polaris appears at the horizon. Polaris cannot be seen below the Equator in the Southern Hemisphere.

Ang OF POLARIS = LAT OF OBSERVER Polaris Changes in Altitude – Polaris is a fixed point above the North Pole. Because of this, in the Northern Hemisphere, the altitude (angle measured in degrees above the horizon) of Polaris tells observer his latitude position. If observer’s latitude changes in the Northern Hemisphere, the altitude of Polaris will exactly match observer’s latitude. Ang OF POLARIS = LAT OF OBSERVER 90º

Earth Facts… The earth is approximately (7,922 mi)  diameter at the equatorial and (7,900 miles)diameter at the polar equatorial The earth has a OBLATE SPHEROID shape The total surface area is 510 Million sq kilometers Water takes up 361 million sq kilometers (approx 70% ) Land takes up 149 million sq kilometers (approx 30%) Tallest mountain from base to peak = Mauna Kea Hawaii 33,480 ft Deepest point in the ocean = Challenger Deep in the Mariana Trench in the Western Pacific Ocean 35,840 ft deep Age of the earth = 4.5 to 4.6 Billion years

What are the 4 big evidences for why we know the earth is NOT flat? What is earths shape?

Atmosphere Hydrosphere Lithosphere Biosphere Earth's Layers EARTH IS MADE UP OF A SERIES OF SPHERES HELD TOGETHER BY GRAVITY ARRANGED FROM LOWEST TO HIGHEST DENSITY Atmosphere Hydrosphere Lithosphere Biosphere

ATMOSPHERE The layer of gases that surrounds the earth above the surface Composed mainly of nitrogen and oxygen Farthest from the earth’s center because it is the least dense Stratified into layers or zones each with its own distinct Characteristics: Troposphere Stratosphere Mesosphere Thermosphere Exosphere

The atmosphere is divided into five layers The atmosphere is divided into five layers. It is thickest near the surface and thins out with height until it eventually merges with space. The troposphere contains half of the Earth's atmosphere. Weather occurs in this layer.  Many jet aircrafts fly in the stratosphere because it is very stable. Also, the ozone layer absorbs harmful rays from the Sun. Meteors or rock fragments burn up in the mesosphere. The thermosphere is a layer with auroras. It is also where the space shuttle orbits.  The atmosphere merges into space in the extremely thin exosphere. This is the upper limit of our atmosphere.

Convection cycle Method of heat transfer in a fluid Think lava lamp! Cold is more dense = sinks Hot is less dense = rises This process results in circular convection cells Also causes pressure gradients which create wind! Also applies to the interior of the Earth

HYDROSPHERE The layer of liquid water that lies between the atmosphere and most of the lithosphere Covers approx 70% of earths surface Average 3.8 Km thickness Mostly hydrogen and Oxygen (H2O)

Crust Mantle Core GEOSPHERE Below the atmosphere and ocean is the geosphere, it is not uniform so we split it into three main parts based on composition Crust Mantle Core Inner outer

GEOSPHERE Most important sections to us… Lithosphere – rigid outer layer of earth including crust and upper mantle Continental Crust – part of the lithosphere is lese dense than the oceanic crust Oceanic Crust – part of the lithosphere, is more dense than the continental crust Asthenosphere – a weak layer of the mantle below the lithosphere where the rock is easily deformed. Magma flow CONVECTION CYCLES in this level is mainly responsible for plate tectonics.

Earth’s Layered Structure

Earth’s Magnetic Field Geodynamo - The Earth’s magnetic field is produced by the geodynamo -Flow in the liquid iron outer core creates a magnetic field Magnetic field - region affected by force emanating from a magnet - grows stronger as separating distance decreases - attracts or repels magnetically charged or moving electrically charged objects - compasses work because Earth is a large magnet

Northern & Southern Lights Form because of our dipole magnetic field!

BIOSPHERE The biosphere is all about life.-biosphere is our living world. This is where all of the trees, bugs, and animals live. The biosphere extends to the upper areas of the atmosphere where birds and insects can be found. It also reaches deep into the ground at a dark cave or to the bottom of the ocean at hydrothermal vents. The biosphere extends to any place that life (of any kind) can exist on Earth.

BIOSPHERE The biosphere is the one place where all of the other spheres of the planet work together. Think about the interactions for a second. The land interacts with the water (hydrosphere). The land interacts with the air (atmosphere and climates). The land even interacts with forces deep inside the Earth and the energy coming to the Earth from space. All of those forces work together to create our living world.

End of Note Questions What is the current theory for how earth was created? Earths shape is most like a _______ List the four evidences that show earth is round. Describe the atmosphere. Describe the hydrosphere. Describe the geosphere. What 2 layers are we most interested in for this class? Describe the biosphere.