Continental crust averages some 25 miles 40 km thick, although it can be thinner or thicker in some areas. Oceanic crust is usually only about 5 miles 8 km thick.
Water fills in low areas of the basalt crust to form the world's oceans. Earth gets warmer toward its core. At the bottom of the continental crust, temperatures reach about 1, degrees Fahrenheit 1, degrees Celsius , increasing about 3 degrees F per mile 1 degree C per km below the crust.
Geologists think the temperature of Earth's outer core is about 6, to 7, degrees F 3, to 4, degrees C and that the inner core may reach 12, degrees F 7, degrees C — hotter than the surface of the sun. Earth's magnetic field is generated by currents flowing in Earth's outer core. The magnetic poles are always on the move, with the magnetic North Pole accelerating its northward motion to 24 miles 40 km annually since tracking began in the s.
It will likely exit North America and reach Siberia in a matter of decades. Earth's magnetic field is changing in other ways, too. Globally, the magnetic field has weakened 10 percent since the 19th century, according to NASA.
But these changes are mild compared to what Earth's magnetic field has done in the past. A few times in every million years or so, the field completely flips, with the North and the South poles swapping places.
The magnetic field can take anywhere from to 3, years to complete the flip, Space. The strength of Earth's magnetic field decreased by about 90 percent when a field reversal occurred in ancient past, according to Andrew Roberts, a professor at the Australian National University.
The drop makes the planet more vulnerable to solar storms and radiation, which could significantly damage satellites as well as communication and electrical infrastructure. When charged particles from the sun get trapped in Earth's magnetic field, they smash into air molecules above the magnetic poles, causing them to glow. This phenomenon is known as the auroras , the northern and southern lights. Earth's atmosphere is roughly 78 percent nitrogen and 21 percent oxygen, with trace amounts of water, argon, carbon dioxide and other gases.
No other planet in the solar system has an atmosphere loaded with free oxygen, which is vital to one of the other unique features of Earth: life. Air surrounds Earth and becomes thinner farther from the surface.
Roughly miles km above Earth, the air is so thin that satellites can zip through the atmosphere with little resistance. Still, traces of atmosphere can be found as high as miles km above the planet's surface. The lowest layer of the atmosphere is known as the troposphere, which is constantly in motion and why we have weather. Sunlight heats the planet's surface, causing warm air to rise into the troposphere. This air expands and cools as air pressure decreases, and because this cool air is denser than its surroundings, it then sinks and gets warmed by the Earth again.
Above the troposphere, some 30 miles 48 km above the Earth's surface, is the stratosphere. The still air of the stratosphere contains the ozone layer, which was created when ultraviolet light caused trios of oxygen atoms to bind together into ozone molecules. Ozone prevents most of the sun's harmful ultraviolet radiation from reaching Earth's surface, where it can damage and mutate life.
As we pass Mars by, it moves backward in the sky then forward again after we have passed. Related: How Big is Earth? Another reason that humans started to realize that we might not be the center of the universe came from looking at parallax , or apparent change in the position of the stars with respect to each other.
For a simple example of parallax, hold up your index finger in front of your face at arm's length. Look at it with your left eye only, closing your right eye. Then close your right eye, and look at the finger with your left. The finger's apparent position changes.
That's because your left and right eyes are looking at the finger with slightly different angles. The same thing happens on Earth when we look at stars. It takes about days for us to orbit the sun. If we look at a star located relatively close to us in the summer and look at it again in the winter, its apparent position in the sky changes because we are at different points in our orbit.
We see the star from different vantage points. With a bit of simple calculation, using parallax we can also figure out the distance to that star. Earth's spin is constant, but the speed depends on what latitude you are located at. Here's an example. The circumference distance around the largest part of the Earth is roughly 24, miles 40, kilometers , according to NASA.
This area is also called the equator. If you estimate that a day is 24 hours long, you divide the circumference by the length of the day. Related: Check out some stunning images of Earth from space. You won't be moving quite as fast at other latitudes, however.
If we move halfway up the globe to 45 degrees in latitude either north or south , you calculate the speed by using the cosine a trigonometric function of the latitude. A good scientific calculator should have a cosine function available if you don't know how to calculate it. The cosine of 45 is 0. That speed decreases more as you go farther north or south. By the time you get to the North or South poles, your spin is very slow indeed — it takes an entire day to spin in place. Space agencies love to take advantage of Earth's spin.
If they're sending humans to the International Space Station, for example, the preferred location to do so is close to the equator. That's why cargo missions to the International Space Station, for example, launch from Florida.
By doing so and launching in the same direction as Earth's spin, rockets get a speed boost to help them fly into space. What are the differences in interior composition between Earth and Mars? How are they different? How are they similar? Once the Earth formed, how did the various and vast variety of life forms begin? All Rights Reserved.
Skip to main content. Login Register. You are here Home » Solar System Objects. How fast is the Earth's rotation at Tucson, AZ? While Newton predicted the wobble of the Earth because it is not a perfect sphere more than years ago, the wobble was not actually measured until by Seth Chandler. There isnt a reliable source that discusses the effects due to earthquakes.
Also, be aware that the numbers quoted in newspapers are calculations, not actual measurements. One could assume that only the largest volcanic eruptions in Earth's history would cause polar changes.
Earth orbits the Sun at an average distance of The orbital speed of the Earth averages On January 3, , when the Earth was at its closest to the Sun perihelion, On July 4, , when the Earth was farthest from the Sun aphelion, Images of the Sun taken at the same time am and location over a one year period An analemma, similar to the one in front of the Flandreau Science Center in Tucson, AZ.
0コメント