1. The Earth

2. The Earth 3rd planet in our solar system Rocky inner planet
Only known planet in the solar system, (or any yet known planets), that currently sustains life.

3. Compostion
Earth has 4 main layers:
Crust
Mantle
Outer Core
Inner Core

4. Crust Outermost layer of the earth, (the part we live on!)
Solid, rocky layer composed of many elements, including oxygen, silicon, aluminum, iron, and magnesium.
Split into many giant plates that float atop the next layer of the earth, the mantle.
The crust can be anywhere from 3 to 46 miles deep:
Thickest parts are under the continents
Thinnest parts are under the ocenas
Does this make sense?

5. Mantle Layer just below the crust Largest layer of the Earth
1800 miles thick of molten rock
Very hot molten rock near the core rises. As it approaches the crust, it cools off, (relatively speaking), and sinks back down. This forms a convection cycle of molten rock continuously rising and sinking in cyclical motions.
This motion in the mantle moves the plates that float on top of it. This causes them to drift together and apart, forming canyons, mountains, earthquakes, etc.

6. Core The center of the Earth is called the core
It is made up of 2 layers, the outer and the inner core
Outer core is molten iron and nickel, 1300 miles thick
Inner core is solid iron, radius of 760 miles
Extreme pressure of other layers compressing the inner core generates great pressure and heat.
Inner core is iron = magnetic. Earth is a large magnet – has poles.

7. Composition, cont.
All natural resources we use today come from the Earth
Therefore, all known elements are part of the composition of the planet, in varying amounts.
Some of the more prominent elements making up Earth include iron, nickel, oxygen, nitrogen, aluminum and calcium.

8. Question: How is it possible for life to exist on Earth?
What makes Earth so unique that life can thrive here and not on any other planets yet known?

9. Reason 1: Atmosphere
Earth has a thick layer of gasses surrounding it called the atmosphere. It is composed mainly of nitrogen, (78%), and oxygen, (21%), with other gases making up the remaining 1%. Earth’s gravity keeps these gases close, and Earth’s unique makeup of water and other materials give it an atmosphere unlike those of other nearby planets. This atmosphere provides Earth with a layer of protection against some of the more harmful rays of the sun and other dangerous elements.

10. Reason 2: Climate
Earth is approximately 93 million miles from the sun.
This happens to be the perfect distance for the Earth to sustain large amounts of water without freezing or evaporating most of it.
It is also the perfect distance to allow a moderate temperature which is not to extreme or harsh, which allows life to thrive.
The sun’s energy drives the weather patterns and cycles of the earth, which move the necessary materials around the planet which living things need.
ENERGY!!

11. Perhaps the most important factor in why life can be sustained on Earth.
While evidence of water on other planets is speculated, Earth is the only known planet to contain so much of it in such perfect conditions.
Approximately 70% of Earth’s surface is covered in water.
Because of Earth’s unique climate, water can exist in all 3 of it’s states of matter, (solid ice, liquid water, gaseous water vapor), at once throughout the planet.
Weather patterns drive the changing of water between its states and moving it around the planet.
Reason 3: Water!

12. How Big is the Earth?
Earth has a radius of 3959 miles, (distance from the surface to the center of the Earth).
Earth’s circumference, (distance around the Earth in a circle), is 24,901 miles.
Earth is the densest, (most tightly packed), planet in our solar system.
The Earth is approximately 4.54 billion years old.

13. How Was The Earth Formed?
There are multiple theories on how earth was formed, but the most accepted theory is that the solar system began as a large nebula; a massive collection of dust and gaseous particles floating in one region of space.
The forces of gravity between them caused them to pull in and collapse on themselves, forcing many of the elements together.
When the sun was formed, (in part by these particles being pulled together), it exerted force on the remaining particles, and they began to clump up. Solar winds, (sun’s energy), swept away smaller particles like hydrogen and helium, leaving only denser materials, which eventually formed the rocky crust of the Earth.
Heavier, denser materials sank down into the Earth, heated up from the pressure and melted, causing mantle to and core to form.
It is hypothesized that many strikes from comets and other celestial bodies, (before the Earth had a strong atmosphere), deposited much of the water onto the Earth’s surface. The optimum distance of the Earth to the sun prevented much of this water from dissipating.