Sea Level and Dry Land
Several terms are used to describe the changing relationships between sea level and dry land. When the term "relative" is used, it means change relative to a fixed point in the sediment pile. The term "eustatic" refers to global changes in sea level relative to a fixed point, such as the centre of the earth, for example as a result of melting ice-caps. The term "steric" refers to global changes in sea level due to thermal expansion and salinity variations. The term "isostatic" refers to changes in the level of the land relative to a fixed point in the earth, possibly due to thermal buoyancy or tectonic effects; it implies no change in the volume of water in the oceans. The melting of glaciers at the end of ice ages is one example of eustatic sea level rise. The subsidence of land due to the withdrawal of groundwater is an isostatic cause of relative sea level rise. Paleoclimatologists can track sea level by examining the rocks deposited along coasts that are very tectonically stable, like the east coast of North America. Areas like volcanic islands are experiencing relative sea level rise as a result of isostatic cooling of the rock which causes the land to sink.
On other planets that lack a liquid ocean, planetologists can calculate a "mean altitude" by averaging the heights of all points on the surface. This altitude, sometimes referred to as a "sea level", serves equivalently as a reference for the height of planetary features.
Read more about this topic: Eustatic
Famous quotes containing the words sea, level, dry and/or land:
“If the sea were ink
For the words of my Lord,
the sea would be spent before the Words of my Lord are spent.”
—Qur’An. The Cave 18:109, ed. Arthur J. Arberry (1955)
“... when you do get a job everybody says, “Well, they wanted a black woman,” which necessarily puts you on a level where you have to prove yourself above being a woman and being black.... Now, I would say, in certain situations, it helped me simply because I was mildly attractive, not because I was black or a woman. That gets you more mileage than anything else.... God help you if you’re not an attractive woman.”
—Theresa Brown (b. 1957)
“But oh, not the hills of Habersham,
And oh, not the valleys of Hall
Avail: I am fain for to water the plain.
Downward, the voices of Duty call—
Downward, to toil and be mixed with the main,
The dry fields burn, and the mills are to turn,
And a myriad flowers mortally yearn,
And the lordly main from beyond the plain
Calls o’er the hills of Habersham,
Calls through the valleys of Hall.”
—Sidney Lanier (1842–1881)
“The great fact was the land itself, which seemed to overwhelm the little beginnings of human society that struggled in its sombre wastes. It was from facing this vast hardness that the boy’s mouth had become so bitter; because he felt that men were too weak to make any mark here, that the land wanted to be let alone, to preserve its own fierce strength, its peculiar, savage kind of beauty, its uninterrupted mournfulness.”
—Willa Cather (1873–1947)