From which sea is it customary to calculate the absolute height. Why countries have different “height from sea level”

Altitude above sea level ... This term, perhaps, is known to every schoolchild. We often meet him in newspapers, on websites, in popular science magazines, as well as when watching documentaries.

Now let's try to give it a more precise definition.

Section 1. Altitude above sea level. general information

This term should be understood absolute altitude or an absolute mark, i.e. such a coordinate in which shows at what height in relation to sea level this or that object is located.

Two other indications of the geographical location of an object are longitude and latitude.

Here, for example, Moscow. The height above sea level of this city is very different: the maximum is 255 m (not far from the metro station “ Teply Stan”), and the minimum - 114.2 m - is located near the Besedinsky bridges, exactly where the Moscow River leaves the city.

In general, if we operate with purely physical measurements, then the height above sea level is nothing more than the vertical distance from, in fact, the single object itself to the average level of the sea surface, which should not be disturbed by either tides or waves.

This value can be both positive and negative. Well, everything is relatively simple here: what is above the sea acquires a plus sign, and below, respectively, a minus sign.

By the way, it is impossible not to note the fact that with an increase in its value, a decrease in atmospheric pressure is observed.

If we talk about our country, then most high point land in the Russian Federation is rightfully considered 5642-meter Elbrus, but the lowest can be called with an absolute height of about 28 m.

Section 2. Altitude above sea level. Most high place on the planet

Well, of course, this is Everest - good famous mountain located in the central part mountain system The Himalayas, just on the border of two South Asian states, Nepal and Tibet.

Today its height is 8848 meters. The words "today" are not accidental. According to scientists, the earth's surface is still continuing to form, so this peak, although imperceptibly, is growing every year.

If you delve into history, then almost immediately you can find information that the first brave conquerors of Chomolungma were ( New Zealand) and Tenzing Norgay (Nepal). They made their truly heroic ascent on May 28, 1953. Since then, Everest has become a kind of Mecca for hundreds and thousands of rock climbers, climbers and other daring adventurers.

Section 3. Altitude above sea level. Most low place on the planet

In this case, things are a little more complicated. The fact is that there are two such points on Earth at once: one of them is the coast Dead Sea- is located on land, and the second bears the name and is located deep under the water column of the Pacific Ocean.

Let's dwell on each of them in more detail.

So, the Dead Sea, as you know, can be found on the border of three countries: Israel, Palestine and Jordan. It is not only the most salty body of water on the planet, but the lowest piece of land.

Now the water level in it is 427 meters, but this is not the limit, because annually, according to experts, it falls by an average of 1 meter.

Altitude above sea level… Moscow, as mentioned above, is located in the range from 114 to 255 m. For us, this is, in principle, the norm. Considering that the capital of the Russian Federation can hardly be called very hilly, it is almost impossible to feel this difference.

Now let's pick up a globe or physical map earth's surface: somewhere deep, deep in pacific ocean, not far from you can see a mark with the inscription So, it goes under water to a depth of a little more than 11 km.

From Wikipedia, the free encyclopedia

Height above sea level, absolute height, absolute mark or altitude(lat. Altitudo- height (points of the earth's surface above ocean level)) - one coordinate in three-dimensional geospace (the other two are latitude and longitude), showing at what level, relative to the sea level taken as zero, this or that object is located.

Examples

see also

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Notes

Links

• // Encyclopedic Dictionary of Brockhaus and Efron: in 86 volumes (82 volumes and 4 additional). - St. Petersburg. , 1890-1907.
• - article from the Great Soviet Encyclopedia (3rd edition)

An excerpt characterizing Altitude

Sea level, position free surface waters of the seas and oceans, measured along a plumb line relative to the conventional reference point. There are “instantaneous”, tidal, average daily, average monthly, average annual, and average long-term sea levels. Under the influence of wind waves, tides, heating and cooling of the sea surface, fluctuations in atmospheric pressure, precipitation and evaporation, and river and glacial runoff, sea levels change continuously. The long-term mean sea level does not depend on these oscillations of the sea surface. The position of the long-term mean sea level is determined by the distribution of gravity and the spatial unevenness of hydrometeorological characteristics (water density, atmospheric pressure, etc.). The average long-term sea level, constant at each point, is taken as the initial level, from which the heights on land are measured. To measure the depths of seas with low tides, this level is taken as the zero depth - the water level mark, from which the depths are measured in accordance with the requirements of navigation. In the USSR, the absolute heights of points on the earth's surface are counted from the average annual level Baltic Sea, defined from zero footstock in Kronstadt.

Lit.: Duvanin A.I., Sea level, L., 1956; Duvanin A. I., Kalinin G. P., Klige R. K., On long-term fluctuations in the level of the oceans, some seas and lakes, “Bulletin of Moscow State University. Series 5. Geography, 1975, No. 6.

ocean surface level is the free water surface of the oceans and seas, close to the geoid shape (Fig. 1).

Rice. 1. Ocean surface level

The initial level of the ocean is the standard from which the absolute height of the land surface and the depth of the seas is measured. In our country, this is the average long-term level of the Baltic Sea near the city of Kronstadt (Baltic height system).

Level fluctuations can be periodic - These are daily fluctuations due to tides and non-periodic- arising from tropical cyclones, tsunamis, etc.

Periods of fluctuations in the level of the World Ocean are short(high-low tide after 6 hours 12.5 minutes) and lengthy or century old(hundreds of years) (Fig. 2).

Rice. 2. Ocean level fluctuations over the past 200 thousand years

Secular changes occur for a number of reasons, such as changes in the volume of water in the ocean or changes in ocean capacity. The first of them occurred during glaciations, when a huge mass of water in the form of ice was conserved on land, and the ocean level dropped by 100-200 m. During the interglacial period, when water entered the ocean as a result of ice melting, the ocean level rose by 20-30 m. According to calculations, as a result of climate warming on Earth, a further increase in the level of the World Ocean by about 30 cm is possible by the middle of the 21st century. The second type of secular fluctuations in the level of the World Ocean is caused by tectonic disturbances of the ocean floor, which entails a change in the volume of the ocean's capacity.