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:
“People can no more be judged by their looks than the sea can be measured in bushels.”
—Chinese proverb.
“Those who profess contempt for men, and put them on a level with beasts, yet wish to be admired and believed by men, and contradict themselves by their own feelings—their nature, which is stronger than all, convincing them of the greatness of man more forcibly than reason convinces them of his baseness.”
—Blaise Pascal (1623–1662)
“Woodlands, meadows,streams and rivers—
Blind to all of it all my life long.
Triolets, villanelles, rondels, rondeaus,
Seeds in a dry pod, tick, tick, tick,”
—Edgar Lee Masters (1869–1950)
“In 1862 the congregation of the church forwarded the church bell to General Beauregard to be melted into cannon, “hoping that its gentle tones, that have so often called us to the House of God, may be transmuted into war’s resounding rhyme to repel the ruthless invader from the beautiful land God, in his goodness, has given us.””
—Federal Writers’ Project Of The Wor, U.S. public relief program (1935-1943)