to measure the depth of a shelf
41Sonar — This article is about underwater sound propagation. For atmospheric sounding, see SODAR. For other uses, see Sonar (disambiguation) …
42Sea surface temperature — Weekly average sea surface temperature for the World Ocean during the first week of February 2011, during a period of La Niña …
43Methane clathrate — Burning ice . Methane, released by heating, burns; water drips. Inset: clathrate structure (University of Göttingen, GZG. Abt. Kristallographie). Source: United States Geological Survey. Methane clathrate, also called methane hydrate,… …
44Italy — /it l ee/, n. a republic in S Europe, comprising a peninsula S of the Alps, and Sicily, Sardinia, Elba, and other smaller islands: a kingdom 1870 1946. 57,534,088; 116,294 sq. mi. (301,200 sq. km). Cap.: Rome. Italian, Italia. * * * Italy… …
45Tide — This article is about tides in the Earth s oceans. For other uses, see Tide (disambiguation). Tidal redirects here. For other uses, see Tidal (disambiguation). High Tide redirects here. For other uses, see High Tide (disambiguation) …
46List of unusual units of measurement — For units of measure primarily used in countries where English is not the main language, see the article specific to that country, a list of which can be found in the systems of measurement article. An unusual unit of measurement is a unit of… …
47Precambrian time — Interval of geologic time from с 3. 8 billion years ago, the age of the oldest known rocks, to 544 million years ago, the beginning of the Cambrian Period. This interval represents more than 80% of the geologic record and thus provides important… …
48Ocean acidification — Change in sea water acidity pH caused by anthropogenic CO2 between the 1700s and the 1990s Ocean acidification is the name given to the ongoing decrease in the pH and increase in acidity of the Earth …
49Denmark — /den mahrk/, n. a kingdom in N Europe, on the Jutland peninsula and adjacent islands. 5,268,775; 16,576 sq. mi. (42,930 sq. km). Cap.: Copenhagen. * * * Denmark Introduction Denmark Background: Once the seat of Viking raiders and later a major… …
50Ice sheet dynamics — describe the motion within large bodies of ice, such those currently on Greenland and Antarctica. Ice motion is dominated by the movement of glaciers, whose gravity driven activity is controlled by two main variable factors: the temperature and… …
