The structure of the Earth is divided into layers. These layers are both physically and chemically different. The Earth has an outer solid layer called the crust, a highly viscous layer called the mantle, a liquid layer that is the outer part of the core, called the outer core, and a solid center called the inner core. The shape of the earth is an oblate spheroid, because it is slightly flattened at the poles and bulging at the equator.
The boundaries between these layers were discovered by seismographs which showed the way vibrations bounced off the layers during earthquakes. Between the Earth's crust and the mantle is a boundary called the moho. It was the first discovery of a major change in the Earth's structure as one goes deeper.
A full explanation of these effects is not yet clear. It seems that the high temperature and pressure cause changes in the crystallization of minerals, so that the composition might be a kind of changing mixture of liquid and crystals.
The moho, properly called the Mohorovičić discontinuity, is the boundary between the Earth's crust and the mantle. It was discovered by Croatian seismologist Andrija Mohorovičić in 1909. He discovered that seismograms of earthquakes showed two kinds of seismic waves. There is a shallow slower wave which arrives first, and a deep faster wave which arrives second. He reasoned that the deeper wave changed speed as it got just below the mantle. The reason it went faster was that the material of the mantle was different from that of the crust.
The discontinuity lies 3040 km below the surface of continents, and less deep below the ocean floors.
Geologists have been trying to get at the Moho for decades. During the late 1950s and early 1960s "Project Mohole" did not get enough support, and was cancelled by the United States Congress in 1967. Efforts were also made by the Soviet Union. They reached a depth of over 15 years, the world's deepest hole, before abandoning the attempt in 1989.
Reaching the discontinuity is still an important scientific target. One proposal considers a self-descending tungsten capsule. The idea is that the capsule would be filled with radioactive material. This would give off enough heat to melt the surrounding rock, and the capsule would be pulled down by gravity.
The Japanese project Chikyū Hakken ("Earth discovery") plans to use a drilling shop to drill down through the thinner ocean crust. On 6 September 2012 Scientific deep sea drilling vessel Chikyu set a new world record by drilling down and obtaining rock samples from deeper than 2,111 metres below the seafloor off the Shimokita Peninsula of Japan in the northwest Pacific Ocean.
Macquarie Island, off Tasmania, is at the meeting-point of two huge oceanic plates: the Pacific Plate and the Indo-Australian Plate. The island is made of material pushed up from deep in the Earth's mantle. It is thought that the green ophiolite rock was formed at the moho, and was brought up by a mid-oceanic ridge. Now it comes to the surface because the two plates are scrunching together. It is the only place on Earth where this is happening at present. There are other places where ophiolite is found, but they were brought up many millions of years ago. Ophiolites are found in all the major mountain belts of the world.
Provisional designation in astronomy
A provisional designation in astronomy is the naming convention of astronomical objects as soon as they are found. The provisional designation is usually replaced by a permanent name once a good orbit has been calculated. With asteroids, so many have been found that many will never be named by the people who found them.
Traffic sign
A traffic sign or a road sign is a sign put at the side of roads to give information to drivers. It can direct people driving where to go or what to do.
A road sign is something that gives information by means of a symbol, or in only 1 or 2 words. It helps people in their vehicles on the road. Some signs include: give way, stop, keep left, no U-turn, no parking, zebra crossing ahead, and much more. Traffic signs are very useful. Without signs and traffic lights there would be many accidents and arguments on the road.
Istituto Nazionale di Statistica
Istituto Nazionale di Statistica is the national statistical institute of Italy. The name translates to 'National Institute of Statistics'. This institute collects information about the country, including counting the people in Italy (the "census"). It is sometimes called "Istat".
Harold Rubin
Harold Rubin (13 May 1932 – 1 April 2020) was a South African-born Israeli visual artist and free jazz clarinettist. He was born in Johannesburg. He became a founding member of the 1980s Zaviot jazz quartet, which recorded albums with the label Jazzis Records and performed at festivals and clubs in Israel and Europe until its break-up in 1989.
Rubin died on 1 April 2020, aged 87.
List of Adventures in Odyssey characters
The following is a list of the characters from the "Adventures in Odyssey" radio program.
List of WTA number 1 ranked players
The Women's Tennis Association (WTA) world number one ranking is a 52-week system based on the total points won by a female professional tennis player, during a WTA season. The WTA started ranking players on 3 November 1975, and 21 women have achieved the number one status in singles and 32 players in doubles.
Please needs updates. We are in 2019
Barbour County, Alabama
Barbour County, Alabama is a county of the U.S. state of Alabama. Its name is in honor of James Barbour, who was Governor of Virginia. As of 2000 the population was 29,038. Its county seat is Clayton.
Barbour County was created on December 18, 1832 from former Creek Indian territory and a portion of Pike County. Its borders were altered in 1866 and 1868. The Election Riot of 1874 occurred near Comer.
Monpazier
Monpazier is a city in France. It is in the Dordogne departement, in Aquitaine. In 1999, 516 people lived there. It has been named one of the most beautiful villages in France by the association Les Plus Beaux Villages de France. It was built as a bastide. For some time, Eleanor of Aquitaine and Richard III lived there.
The city was founded by Edward I of England in 1284. It is of rectangular design, built around a main square.
The city is about half-way between Bergerac and Sarlat-la-Canéda. Each city is about 45 km away. The River Dropt runs through the city.
Sarlat-la-Canéda
Sarlat-la-Canéda (), or simply Sarlat, is a town and commune in southwestern France, in the region of Aquitaine. It is a subprefecture of the Dordogne department.
The city developed around a Carolingian Benedictine abbey in the 13th century. The abbey already existed in the 9th century. it was part of the six great abbeys of the old province of Périgord. The others were Paunat, Belvès, Saint Front de Périgueux, Brantôme and Terrasson. The Carolingian abbey was the only one to be spared by the Vikings because it does not lie on the Dordogne river or its tributaries. In 1317, Sarlat became the seat of a bishop.
The city was badly damaged in the Hundred Years' War. After several conflicts it was rebuilt in Renaissance style between 1450 and 1500. In the middle of the 17th century, the city lost political influence and became poorer.
On 1 March 1965, the "communes" of Sarlat and of La Canéda were combined in one "commune" with the name of Sarlat-la-Canéda.
The "commune" of Sarlat-la-Canéda has an area of and its average altitude is ; at the city hall, the altitude is .
Sarlat-la-Canéda is surrounded by the "communes" Tamniès, Marquay. Marcillac-Saint-Quentin, Proissans, Sainte-Nathalène, Saint-Vincent-le-Paluel, Carsac-Aillac, Vitrac, Vézac and Saint-André-d'Allas.
Sarlat-la-Canéda has an oceanic climate with template summers (Köppen climate classification: Cfb).
The inhabitants of Sarlat-la-Canéda are known, in French, as "Sarladais" (women: "Sarladaises").