When The Earth Starts Moving…

THE EARTH

Earth is the third planet from the Sun and the fifth largest:

 orbit: 149,600,000 km (1.00 AU) from Sun diameter: 12,756.3 km mass: 5.972e24 kg
The Earth as seen from space

Earth is the only planet whose English name does not derive from Greek/Roman mythology. The name derives from Old English and Germanic. There are, of course, hundreds of other names for the planet in other languages. In Roman Mythology, the goddess of the Earth was Tellus – the fertile soil (Greek: Gaia, terra mater – Mother Earth).

It was not until the time of Copernicus (the sixteenth century) that it was understood that the Earth is just another planet.
Earth, of course, can be studied without the aid of spacecraft. Nevertheless it was not until the twentieth century that we had maps of the entire planet. Pictures of the planet taken from space are of considerable importance; for example, they are an enormous help in weather prediction and especially in tracking and predicting hurricanes. And they are extraordinarily beautiful.
The Earth is divided into several layers which have distinct chemical and seismic properties (depths in km):
-0- 40 Crust 40- 400 Upper mantle 400- 650 Transition region 650-2700 Lower mantle 2700-2890 D'' layer 2890-5150 Outer core 5150-6378 Inner core 

 


The crust varies considerably in thickness, it is thinner under the oceans, thicker under the continents. The inner core and crust are solid; the outer core and mantle layers are plastic or semi-fluid. The various layers are separated by discontinuities which are evident in seismic data; the best known of these is the Mohorovicic discontinuity between the crust and upper mantle.


Earth as seen from the Moon

Most of the mass of the Earth is in the mantle, most of the rest in the core; the part we inhabit is a tiny fraction of the whole (values below x10^24 kilograms):

 

 atmosphere = 0.0000051 oceans = 0.0014 crust = 0.026 mantle = 4.043 outer core = 1.835 inner core = 0.09675 

The core is probably composed mostly of iron (or nickel/iron) though it is possible that some lighter elements may be present, too. Temperatures at the center of the core may be as high as 7500 K, hotter than the surface of the Sun. The lower mantle is probably mostly silicon, magnesium and oxygen with some iron, calcium and aluminum. The upper mantle is mostly olivene and pyroxene (iron/magnesium silicates), calcium and aluminum. We know most of this only from seismic techniques; samples from the upper mantle arrive at the surface as lava from volcanoes but the majority of the Earth is inaccessible. The crust is primarily quartz (silicon dioxide) and other silicates like feldspar. Taken as a whole, the Earth’s chemical composition (by mass) is:

 34.6% Iron 29.5% Oxygen 15.2% Silicon 12.7% Magnesium 2.4% Nickel 1.9% Sulfur 0.05% Titanium

 

The Earth is the densest major body in the solar system.

 

The other terrestrial planets probably have similar structures and compositions with some differences: the Moon has at most a small core; Mercury has an extra large core (relative to its diameter); the mantles of Mars and the Moon are much thicker; the Moon and Mercury may not have chemically distinct crusts; Earth may be the only one with distinct inner and outer cores. Note, however, that our knowledge of planetary interiors is mostly theoretical even for the Earth.


Earth as a map of the world

Unlike the other terrestrial planets, Earth’s crust is divided into several separate solid plates which float around independently on top of the hot mantle below. The theory that describes this is known as plate tectonics. It is characterized by two major processes: spreading and subduction. Spreading occurs when two plates move away from each other and new crust is created by upwelling magma from below. Subduction occurs when two plates collide and the edge of one dives beneath the other and ends up being destroyed in the mantle. There is also transverse motion at some plate boundaries (i.e. the San Andreas Fault in California) and collisions between continental plates (i.e. India/Eurasia). There are (at present) eight major plates:

  • North American Plate – North America, western North Atlantic and Greenland 
  • South American Plate – South America and western South Atlantic
  • Antarctic Plate – Antarctica and the “Southern Ocean”
  • Eurasian Plate – eastern North Atlantic, Europe and Asia except for India
  • African Plate – Africa, eastern South Atlantic and western Indian Ocean
  • Indian-Australian Plate – India, Australia, New Zealand and most of Indian Ocean
  • Nazca Plate – eastern Pacific Ocean adjacent to South America
  • Pacific Plate – most of the Pacific Ocean (and the southern coast of California!)

There are also twenty or more small plates such as the Arabian, Cocos, and Philippine Plates. Earthquakes are much more common at the plate boundaries. Plotting their locations makes it easy to see the plate boundaries (right).

The Earth’s surface is very young. In the relatively short (by astronomical standards) period of 500,000,000 years or so erosion and tectonic processes destroy and recreate most of the Earth’s surface and thereby eliminate almost all traces of earlier geologic surface history (such as impact craters). Thus the very early history of the Earth has mostly been erased. The Earth is 4.5 to 4.6 billion years old, but the oldest known rocks are about 4 billion years old and rocks older than 3 billion years are rare. The oldest fossils of living organisms are less than 3.9 billion years old. There is no record of the critical period when life was first getting started.

 71 Percent of the Earth’s surface is covered with water. Earth is the only planet on which water can exist in liquid form on the surface (though there may be liquid ethane or methane on Titan’s surface and liquid water beneath the surface of Europa). Liquid water is, of course, essential for life as we know it. The heat capacity of the oceans is also very important in keeping the Earth’s temperature relatively stable. Liquid water is also responsible for most of the erosion and weathering of the Earth’s continents, a process unique in the solar system today (though it may have occurred on Mars in the past).

And when the earth starts moving, it is time to get out of the way…

Click any of the images to see the video… Brace yourself!

Comments

  1. Brilliant I love these kinds of posts that tell you cool FACS about the world.

  2. 12kilroy says:

    Great post. That must have been terrifying for the people there.

  3. I launched a full investigation, and discovered that a local dentist was using a very high-pitched drill– that’s what caused the landslide.

    As I suspected. : P

  4. Wow! Informative AND amazing! Great job Dolly! :)

  5. Reblogged this on Scribbles in the sand.

  6. I only wish man would appreciate our planet more. So sad, the horrible things we do to our environment, as a thank you for all of her wonderful gifts to us. :)

  7. Thank you professor Honeybee…

  8. MONYA NEBA says:

    Very interesting…thanks for sharing :)

  9. Amazing video… I’ve never seen simple earth do that just that way. I’ve seen lava flow like that, and I live in California, so I’ve seen how earthquakes behave, and that can be pretty strange. But I haven’t seen that phenomenon before, where the earth looked as if it were being pushed from behind, for such a long period of time. Most of the quakes I’ve been in lasted mere seconds, or at most, like the big one in 1905 in SF, which shook for more than a minute, reportedly. But that earth was still moving after two and a half minutes when the film ended. Very strange, and doesn’t that prove the old saying about truth being stranger than fiction!…. Great post, I love off the wall stuff like this…. thanks again, kiddo….

  10. Informative and interesting….what a scary video, those poor ppl….I feel for them!

Trackbacks

  1. [...] visiting the always interesting All About Lemon has a most exciting piece about the Earth. Visit the site and then click any picture of the Earth [...]

  2. [...] When The Earth Starts Moving… (allaboutlemon.com) [...]

I'm delighted to hear from you :) Merci, beaucoup to all who clicked LIKE...

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Follow

Get every new post delivered to your Inbox.

Join 4,047 other followers

%d bloggers like this: