Earth is a wonderful planet that has many interesting and distinct features. Besides being the only planet in our solar system to harbor life, Earth has many interesting qualities.
1. Earth is the only planet within our solar system that contains water in all three of its forms. Liquid, gas and ice can all be found on the planet surface at any given time. Water is also the major component of the earth’s outer surface. 71% of the surface is covered in water or ice and land makes up a mere 29%. Water is the most important element for life on the planet and every living object needs water for life. Because of the water content, from space Earth would be viewed as the brightest of the planets. This is due to the sun’s reflection on the water.
2. The earth is getting slower as it ages. This slowing causes the earth to add time to each day. Over the course of several million years the regular earth day will change from 24 hours to 26. The average time it takes for the earth to orbit the sun is 365 ¼ days. Because of this additional quarter of a day every four years a day is added to the calendar. The next time we will have an additional day is February 29, 2012.
3. Earth has two co-orbital satellites. Everyone is aware that the moon orbits the planet, but not many people realize we also have two asteroids that orbit the planet. 3753 Cruithne is an asteroid that does not actually orbit the earth, but follows the same orbital path, creating the illusion that it is orbiting the planet. This asteroid is about 5 km across. The second asteroid is known as 2002 AA20. This object makes a horseshoe path around earth and comes close to the planet about every 95 years. Scientists believe in about 600 years the asteroid will enter into a permanent orbit around the planet.
4. El Azizia, Libya is the hottest place on Earth. El Azizia has had recorded temperatures of 136 degrees and at some point, though not officially recorded, have had reports of 150 degree weather. This is measures by the air temperature at 5 feet above the ground. Temperature on the ground can be considerably hotter. Antarctica is the coldest place on earth with a record temperature recorded at 128 degrees below zero.
5. Earth is the only planet in our solar system that is geologically active. This is very important for the sustaining of life on the planet. When the earths plates shift, sediment at the bottom of the oceans are sucked into the molten core. This eliminates all the excess carbon that comes from the decay of plants and animals on the oceans floor. By burning off this excess carbon the planet is able to maintain a stable environment for life. Failure to do this would cause the planet to become very hot.
6. The wettest place on Earth is Cherrapunji, India. On average the town receives 450 inches of rain each year. The heavy rains are due to its positioning Khasi Hills. The monsoon winds that come into the area each year bring this incredible rainfall. The driest place on the planet is the Atacama Desert in Chile. Some places in this desert have not had rainfall in over 400 years. On average, the desert receives less than a tenth of a centimeter of rain each year. Antarctica, despite its cold weather and ice is actually considered a desert. The area only receives about 2 inches of rain a year.
7. Panama, because of its location, is the only place where someone can go to watch the sun rise on the Pacific Ocean and set on the Atlantic Ocean. There are a total of five oceans on the earth: Atlantic, Pacific, Indian, Southern and Arctic.
8. The largest city on Earth is Seoul, South Korea. This city has over 10 million inhabitants. The most spoken language on earth is Mandarin with over a billion people speaking the language. There are 6 billion people on Earth with almost 7000 known and current languages spoken.
9. The lowest point on the earth’s surface is located in the Dead Sea. The Dead Sea is 13,000 feet below sea level. On the opposite end of the spectrum, Mt. Everest is the highest point on the planet reaching over 29,000 feet above sea level. Lake Baikal, located in Siberia is the world’s oldest and deepest lake. Dated at over 25 million years old, the depth of the lake exceeds 1600 meters.
10. Earth’s name comes from a combination of old English and Germanic language. It is the only planet in our solar system that was not named for a mythological god. In the ancient languages it was often referred to as Gaia, the goddess of soil, terra mater which translates to mother soil or Tellus another version of the word fertile soil.
What is the Mohorovicic Discontinuity used for?
The Mohorovicic Discontinuity, or “Moho” as it is popularly called, is the boundary between the earth’s crust and the earth’s mantle. The Moho was discovered in 1909 by Andrija Mohorovicic, a Croatian seismologist (earthquake specialist). Scientists understood that the earth is made up of a series of layers, all of different materials and at different states of development. The three main layers are the very thin, brittle crust, the mantle and the core. The core actually forms only 15 percent of the earth’s volume, while the mantle makes up 84 percent. The crust comprises the remaining 1 percent.
As the earth’s crust is easily accessible, scientists have been able to study its structure and composition extensively. Within the crust, rocks are moved about to form patterns through various geologic processes, including eruption and intrusion of lava, consolidation of rock particles, erosion and solidification of porous rock. Pressure from the earth causes rocks to shift and collide with each other, forming the basis for mountains and volcanoes on the surface.
Less is known about the earth’s mantle. Scientific knowledge has been gleaned from the analysis of earthquake waves; magnetic, heat flow and gravity studies; and laboratory experiments on rocks and minerals. The boiling, molten rock that erupts by some volcanoes originates in the mantle, which is between 100 and 200 kilometers below the earth’s surface.
When pressures inside the earth force the weaker points of the rocky layers out of alignment, a series of waves make their way through the layers of earth, and an earthquake erupts on the earth’s surface. Mohorovicic discovered that these waves, called seismic waves, travel comparatively slowly through the actual crust of the earth. However, when they reach the lowest level of the crust, which is the area just above the next layer called the mantle, the waves increase their speed dramatically and sometimes even change direction. This proved that the earth’s crust is different from the mantle beneath. The point at which the waves change, the area between the crust and the mantle, is known as Mohorovicic Discontinuity.
Using seismographs, which are sensitive shock recording machines, scientists have established that the Moho is between 20 and 25 miles deep in continental areas, but only three miles deep under some oceans. Research has found that oceanic crust has a relatively uniform thickness while continental crust is thinner under plains and thickest under mountain ranges.
While scientists rely on the Moho for experiments and data, no one has ever been able to penetrate deep enough into the earth to actually see the Moho. Drilling to that depth is very difficult and expensive because of the extreme pressure and temperature. During the late 1950s and early 1960s, the U.S. National Science Foundation planned to drill through the ocean floor to reach this boundary. However, the operation was canceled before it really began. The closest scientists have come to date is a hole that has been dug to a depth of about 12 kilometers during the course of 15 years on the Kola Peninsula in the Soviet Union.
There are a few rare locations where forces beneath the earth have exposed mantle material. Scientists have then been able to study rock that was formerly at the crust-mantle boundary. Scientists’ knowledge of the composition and structure of the earth is constantly being improved by geologists doing laboratory experiments on rocks at high pressure and using computers to analyze earthquake records. Science continues to place importance on reaching the Mohorovicic Discontinuity. In fact, a more recent idea has United States and Japanese scientists each proposing to send a self-descending capsule powered by radiogenic heat underground to explore the Moho and the earth’s upper mantle.