Earthquakes essays

Earthquakes essays The earth we live on consists of the ocean, and the continents. Below the ocean and continents we have the earths crust, which can very in length for miles. Under the earths crust we encounter small breaks in the earth, which is caused by the slow movement of mantle. With this movement we find the plates of the continent breaking apart and causing earthquakes (Nicholls, Bill 2). The earths mantle roughly extends about 1,798 miles. The density of the mantle changes because of pressure and heat. The further down the mantle is the more pressure and heat we encounter (Nicholls, Bill 1). The worlds lithosphere covers the entire earth (outer shell) and can be broken in many places to form what is called plates. These continental and oceanic plates are constantly moving and they never stop. With the concurrent movement of our lithosphere many mountains, volcanoes, and earthquakes will be created because of these plates (Spall, Henry 1). Oceanic plates can also cause earthquakes. Although it seems odd we encounter earthquakes, under water they still occur. Small narrow ridges within the seafloor are cracking because the crust is in constant motion, and with constant motion the oceanic crust is breaking away. Volcanic eruptions from the earths mantle will eventually fill these cracks and form a replaceable crust (Spall, Henry 1). Below the earths crust we have what is called a magnetic field, which is created by the solid form of basaltic. Basaltic is a magnetized material that has reversed the earths polarity 170 different times within the last 80 million years. With the magnetic field being in occurrence this can aid plate tectonics into an earthquake (Spall, Henry 2). In our world we have what is called major crustal plates we now know that there are seven major crystal plates, subdivided into a number of smaller plates (Spall, Henry 2). The small plates are ab...

A Profile of Greek Mathematician Eratosthenes

A Profile of Greek Mathematician Eratosthenes Eratosthenes (c.276-194 B.C.), a mathematician, is known for his mathematical calculations and geometry. Eratosthenes was called Beta (the second letter of the Greek alphabet) because he was never first, but he is more famous than his Alpha teachers because his discoveries are still used today. Chief among these are the calculation of the circumference of the earth (note: the Greeks did know the earth was spherical) and the development of a mathematical sieve named after him. He made a calendar with leap years, a 675-star catalog, and maps. He recognized the Niles source was a lake, and that rains in the lake region caused the Nile to flood. Eratosthenes - Life and Career Facts Eratosthenes was the third librarian at the famous Library of Alexandria. He studied under the Stoic philosopher Zeno, Ariston, Lysanias, and the poet-philosopher Callimachus. Eratosthenes wrote a Geographica based on his calculations of the circumference of the earth. Eratosthenes is reported to have starved himself to death at Alexandria in 194 B.C. Writing of Eratosthenes Much of what Eratosthenes wrote is now lost, including a geometrical treatise, On Means, and one on the mathematics behind Platos philosophy, Platonicus. He also wrote the fundamentals of astronomy in a poem called Hermes. His most famous calculation, in the now lost treatise On the Measurement of the Earth, explains how he compared the shadow of the sun at Summer Solstice noon in two places, Alexandria and Syene. Eratosthenes Calculates the Circumference of the Earth By comparing the shadow of the sun at Summer Solstice noon at Alexandria and Syene, and knowing the distance between the two, Eratosthenes calculated the circumference of the earth.The sun shone directly into a well at Syene at noon. At Alexandria, the angle of inclination of the sun was about 7 degrees. With this information, and knowing that Syene was 787 km due south of Alexandrian  Eratosthenes calculated the circumference of the earth to be 250,000 stadia (about 24,662 miles).