Geographic extremes: New York, the South Pole, and Novosibirsk

Oceanography

Identifying the current location

New York belongs to the state bearing the same name and is situated on the north-eastern coast of the U.S.A., at the point where the Hudson River flows into the Atlantic Ocean. The city's geographical coordinates are latitude 40047'N and longitude 73058' W. The city is renown for its cultural aura, but also for its financial, business, and trading organizations which play a major role to the national and world economy (http://en.wikipedia.org/wiki/New_York_City).

The point most surrounded by water

When I looked at the globe, the land which seemed to be most surrounded by water was Antarctica. The continent is placed in the middle of the Southern Ocean or South Polar Ocean (which changed its name after being initially labeled as the Antarctic Ocean) which is considered to be the fourth largest water area in the world. If I had to choose a specific location on this land, I would probably opt for the South Pole which has latitude of 90 degrees south and a longitude which can be described by any of the meridians converging at the pole. The most southern point of the Earth was first reached by people on December 14, 1911, as a result of the expedition organized by the Norwegian Roald Amundsen and his companions who named the camp Polheim. Their observations and the data conveyed by the surveillance station emphasized that the South Pole's climate is one of the coldest on the Earth, mainly because of the high altitude created by the 3000 meter-thick ice cap which tops the land lying near the sea level. The absence of sunlight, in the winter, and the low position that the sun has in the sky, during the southern summer, explain temperatures raging from -650C in the cold season to -250 C. In the warm one. The climate also resembles the desert profile because of the strong winds blowing the snow and the rare precipitations (http://en.wikipedia.org/wiki/South_Pole).

The point most surrounded by land second look at the globe led me to the conclusion that Novosibirsk is the point where I would be most surrounded by land. Russia's third city after Moscow and Saint Petersburg and Siberia's largest town, at the same time, has a latitude of 82.93E and a longitude of 55.02N. It was founded in 1893 and until 1925 was named Novonikolayevsk, after Tsar Nicholas II. The city is situated along the Ob River, comprising a land area of 447.2km2 and a water area of 0 km2. It has a continental climate, defined by severe winters with temperatures ranging from -180C to - 200C, and hot, dry summers with temperatures between 200C and 250C. The town is the administrative center of Siberia Federal District and is famous for its cultural activities displayed by the local opera, ballet companies, art galleries, museums, and so forth (http://en.wikipedia.org/wiki/Novosibirsk).

Comparison between the land and water areas in the northern and southern hemisphere

If one takes a look at the world's map, he can easily notice that the northern hemisphere is more generous in terms of land while its southern counterpart boasts a larger water area. In other words, if we focus on the half above the equator, we will observe that this includes North, Central and a part of South America, Europe, Asia and the largest part of Africa. When moving towards the half below the equator, the only land areas consist of Australia and the islands around it, South Africa, some of the islands situated in the south-eastern part of Asia, and most of South America.

Flying between the two most distant points

If I were to fly over the continents, between the most distant points, these would probably be Stockholm and Sydney. My route measures almost 13700 miles (22043.3 km) and its duration ranges between 24 and 31 hours if I travel by a jet aircraft with a high cruising speed of 700km/h, or respectively, 900 km/h. The flight would cover three continents: Europe, Asia and Australia (http://www.mapsofworld.com/utilities/world-airdistance-locator.htm).

Sailing between the two most distant points

If I were to sail between the two most distant points, I would opt for New York and Sydney. My ship would sail over the Atlantic Ocean until reaching a South African harbor (Cape Town, for instance) and, afterwards, would cover the Indian Ocean, until the Australian port of Sydney. If I were to fly between the same two points, the distance would measure 12052 miles (http://www.mapsofworld.com/utilities/world-airdistance-locator.htm).

Convergent plate boundaries

Plate boundaries fall into three categories: convergent or destructive boundaries which push against each other, divergent boundaries which move apart from each other and transform boundaries which "slip past each other, side to side" (http://en.wikipedia.org/wiki/Convergent_boundary).

The convergent group includes three types of plate boundaries: continental-oceanic, oceanic-oceanic, and continental-continental. The first type consists of the meeting between a light continental plate and a dense oceanic one. Obviously, the latter will sink into the astenosphere because of its higher weight. The temperature and pressure that the sinking plate meets on its downward trajectory causes several chemical reactions which melt the mantle above the subducting plate. The liquid rock resulted (magma) has two options: either it solidifies below the surface and forms the basis of a mountain range (like in Sierra Nevada's case), or it breaks through and forms a volcanic mountain range. An edifying example is the small plate called Juan de Fuca which sinks beneath North America, causing earthquakes of significant magnitudes.

The second type of convergence occurs when two oceanic plates collide. Because both of them are heavy, the one that sinks is "the older, colder, and denser plate" (http://en.wikipedia.org/wiki/Convergent_boundary).The result of the subduction is the rise of a volcanic mountain chain out of the ocean, a formation that specialists identify as island arcs. An example is the Aleutian Peninsula of Alaska which appeared after the subduction of the northern part of the Pacific Plate of Alaska and the north-western part of the North- American Plate.

The third category of convergence is caused by the collision between two continental plates. As both of them are light, none can sink. Consequently, they mount each other and form a towering mountain range. A perfect example may be the Himalayas which were born because the Eurasian Plate and the Indian Plate collided (http://en.wikipedia.org/wiki/Convergent_boundary).

The correlation between ocean depths and plate tectonic processes

As convergent and divergent boundaries have just been described in the paragraph above, the only remaining concept that must be clarified is the abyssal plain. This is a flat area which covers almost half of the ocean floor, boasting depths that range between 2200 and 5500 meters (http://en.wikipedia.org/wiki/Abyssal_plain).If one relates these three concepts to ocean depths, the most pertinent conclusions would be the following: divergent boundaries move apart from each other and create a higher ocean depth, convergent boundaries collide and cause the decrease of the ocean depth, while abyssal plains are flat, so the depth of the oceans remains the same.

Swells, breaking surf, tsunami

Swells may be defined as "a long series of ocean waves, generally produced by wind, and lasting after the wind has ceased" (http://en.wikipedia.org/wiki/Swell).They may be generated thousand of miles away from the beach by tropical storms or wind systems. Such a genesis explains their higher stability in direction and frequency, and the major attractiveness that they exert on surfers. Thus, swells are the so called wave trains which display considerable wavelength or period. This is a parameter measuring "the average length of time between each wave in a set" (http://en.wikipedia.org/wiki/Swell).For instance, the first waves in a swell might have 20 to 25 seconds, while the second group which might arrive 2 days later, could have a period of 17 seconds. The wavelength is the natural consequence of the energy invested by the wind into the ocean. A swell's strength to surpass obstacles depends on the Aeolian energy. Therefore, short-period swells, measuring up to 14 seconds, are fragile in front of winds or seas, while long-period swells, measuring over 14 seconds, prove to be more resistant (Collins, 2007).

The swell speed (in miles per hour) may be calculated as a product between the period (in seconds) and 1.75. Thus, at a 10-second period, the speed is 17.5 mph; at a 12-second period, the speed is 21 mph and so on (http://www.rodndtube.com/surf/info/SwellSpeed.shtml).The depth (in feet) at which waves feel the ocean floor may be calculated as a product between the square number of seconds between swells and 2.256. For example, a 20-second period swell will have a depth of 1024 feet (Collins, 2007).

Sometimes waves have the tendency to break when they encounter shallow waters, when two opposite systems meet or when winds become so strong that they are able to remove the wave top. Breaking waves are very dangerous because they can overturn boats and crush ships due to the impressive pressure of up to 50 or 100 kilopascals (4-9 short tons per square yard). Their main treat refers to the speed of the wave crest which is equal to that of the wave itself. Consequently, the base isn't capable of supporting the top and this failure results in wave breaking (http://seriesdrogue.com/coastguardreport/breaking_waves.htm).

Tsunamis occur where the sea floor undergoes severe deformations that vertically displace enormous amounts of water. Some of the causes responsible for this phenomenon may be earthquakes, meteorite impacts, eruptions, underwater explosion and so forth. Unlike surf swells, tsunamis display a huge energy that remains fairly constant, despite the great distance they travel. Moreover, they behave as shallow waters with an average speed of 400 to 500 mph and extremely long periods or wavelength. Therefore, tsunamis may not be even noticed by ships sailing in the open ocean. The striking effect is released when reaching