The earth is not perfectly round. Its shape changes with time.
(Credit: U.S. Geological Survey, Geologist Vic Baker)
Sir Isaac Newton proposed that the Earth was not perfectly round, he suggested its shape to be an oblate spheroid; a sphere that is squashed at its poles and swollen at the equator. Earth's equatorial diameter is 12,756 km (7,926 miles); its pole to pole diameter is 12,713 km (7,898 miles).
The crust, mantle, outer core and inner core are different layers in the Earth. Geologist Vic Baker at the University of Arizona, Tucson explained that Earth's plasticity has similar effect as spinning a bit of silly putty which allows it to deform very slightly though, Earth's resilience is much less than that of the silicon plastic clay so familiar to children.
Mass of the earth shift inwards.
Many mountains/valleys emerge and disappear due to plate tectonics.
The changing weight of the ocean and atmosphere,
All above factors contribute to variation in Earth's shape with time.
Do you recall why the continents are at a higher elevation than the ocean floor?
(Credit: National Science Foundation)
Density is one of the most essential physical properties that cause the formation of layers in the earth. The crust is having less density so it floats on the denser layer, the mantle. Both oceanic crust and continental crust are less dense than the mantle, but the oceanic crust is denser than continental crust. The continental crust floats higher on the mantle due to its lower density.
Every layer has different density because they are made of various kind of rocks. The continental crust consists primarily of rocks with the composition similar to granite, whereas the oceanic crust is made mostly of rocks with the composition of basalt. Partial melting of the mantle at mid-ocean ridges causes the formation of the oceanic crust whereas lesser dense rocks (continental crust) is formed by even more cycles of partial melting over time.
What cause an earthquake?
(Credit: Scientific American & Khan Academy )
Most of the destructive vibrations of the earth's surface are caused by dislocation of the crust. Earth's crust is divided into massive rocky pieces called tectonic plates. These plates float on the mantle and are constantly moving slowly. The mantle transfers heat from the hot core at the planet's center to the colder surface; this happens by either conduction or convection.The mantle’s convective motions break the lithosphere into plates and shift them around the surface of the planet which cause the plates to move relative to each other insightful ariticle here. If these plates slide past or crash into each other, the earth shakes and quakes.
According to the United States Geological Survey, there are more than 7 million earthquakes every year. Most of these are extremely weak to be noticed.
The deepest man-made hole in the earth's surface is deeper than Mariana Trench.
(Credit: iflscience.com )
Well, you heard it right. It was an effort by Soviet scientists to pierce a hole in the earth's crust, and they kept on digging for 24 years. The effort was begun to pierce a hole into the earth's crust to reach the earth's deepest point but they had to stop deep into the earth's crust, which is only about 12 km deep. The bore is called Kora Superdeep borehole, and located on the Kola Peninsula of Russia. Some of the key observations collected from this experiment were;
- There's much water down there
- The Earth contains gases
- There is no basalt under the continent's granite
- There are fossils in granite below the earth's surface( > 6,700 meters) and last but not the least, there is nothing like hell beneath your foot :-)
The aritcle was originally published by me on Linkedin in the year 2016. After few edits, I am publishing it here. If you still wish to test originality, you can contact me. I have collected information from various resources as mentioned.
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