to: Intro, Motions of
the Earth, Characteristics Page 1,
Page 2: Characteristics
Page 2, Changes
The Earth is one of the most
fascinating of all planets. It is the home of human beings and other
living things. Why can this planet support life? The earth is a sphere
covered with rock, water, soil and air. It is just the right distance
away from the sun. We all need sunlight and warmth for life. If the
earth was too close, it would be too hot for living things and if it
were too far, it would be too cold. Also, water is a key element for all
living things, and the earth has plenty.
The crust forms the surface of the
earth. It is a thin layer of rock. Life on earth is either on the crust
or in the water, which covers 70 percent of it. Below the crust is hot
rock and below this is a ball of metal at the center.
The earth is the fifth largest
planet and the third planet from the sun. Its diameter is 8,000 miles
long. The earth is about 93 million miles from the sun. The atmosphere
of Earth contains enough oxygen to sustain life. This can be compared to
with other planets such as Mars, where it consists of only carbon
Earth (right) with Hurricane Andrew taken by the NOAA GOES-7 satellite
on August 25, 1992.
MOTIONS OF THE EARTH:
The earth is continuously moving.
It has three motions; 1) spins, 2)travels around the sun, and 3)moves
through the Milky Way. We use the spinning and traveling to measure our
days and years. The earth spins around it's axis. This spin makes it
seem that the sun is moving from east to west. One day is the time it
takes for the earth to spin once. It takes 23 hours, 56 minutes, and
4.091 seconds for the earth to do this. This length of time is called a
Next is the traveling. The earth
travels around the sun in 365 days, 6 hours, 9 minutes and 9.54 seconds.
This is called a sidereal year. The earth travels 595 million miles
around the sun at a speed of 66,600 miles per hour. The path the earth
takes to move around the sun is called an orbit.
The Milky Way spins as well. It
revolves around the center of the Galaxy at 155 miles per second! The
earth only has one moon. Its diameter is 2,160 miles.
The earth has a North and South
Pole. Halfway between these poles is the equator. The earth is not
perfectly spherical. It is slightly flatter at the poles.
The earth's atmosphere consists of
78% Nitrogen, 21% Oxygen, and 1% argon and other gases. It also contains
water vapor and dust particles. Clouds float in the troposphere, the
lowest part of the atmosphere. The air gets thinner as it gets further
from the earth.
The earth's crust is about 5 miles
thick under the oceans and about 25 miles thick under the continents.
Temperatures can reach up to 1600 degrees Fahrenheit. This crust is made
of three types of rock; 1) igneous, 2) sedimentary, and 3) metamorphic.
Igneous rocks are formed when melted rock such as lava cools and
hardens. Sedimentary rock develops from material such as plants or
animals. Metamorphic rocks formed deep in the crust by heating of other
rocks. The crust consists of oceanic and continental crust.
Beneath the crust is a sphere of
hot rock and metal. It is divided in to the mantle, outer core, and the
inner core. The mantle is a layer of rock under the crust. It is about
1,800 miles deep and made of silicon, oxygen, aluminum, iron and
magnesium. The temperature ranges from 1,600 degrees Fahrenheit to about
8,000 degrees. The outer core is under the mantle. It is about 1,400
miles thick and consists of melted iron, oxygen and sulfur. The
temperature range is 8,000 degrees to 11,000 degrees. The inner core is
the center of the earth. It is believed that this is consisted of solid
iron mixed with other elements such as oxygen and sulfur. The
temperature can range up to 13,000 degrees Fahrenheit.