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: Sea Level
Famous quotes containing the words sea, level, dry and/or land:
“should some limb of the devil
Destroy the view by cutting down an ash
That shades the road, or setting up a cottage
Planned in a government office, shorten his life,
Manacle his soul upon the Red Sea bottom.”
—William Butler Yeats (1865–1939)
“For him nor deep nor hill there is,
But all’s one level plain he hunts for flowers.”
—Unknown. The Thousand and One Nights.
AWP. Anthology of World Poetry, An. Mark Van Doren, ed. (Rev. and enl. Ed., 1936)
“In ten thousand years the Sierras
Will be dry and dead, home of the scorpion.”
—Gary Snyder (b. 1930)
“We come and go, but the land is always here. And the people who love it and understand it are the people who own it—for a little while.”
—Willa Cather (1873–1947)