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:
“And one rose in a tent of sea and gave
A darkening shudder; water fell away;
The whale stood shining, and then sank in spray.”
—Yvor Winters (1900–1968)
“Insurrection:... insurrection as soon as circumstances allow: insurrection, strenuous, ubiquitous: the insurrection of the masses: the holy war of the oppressed: the republic to make republicans: the people in action to initiate progress. Let the insurrection announce with its awful voice the decrees of God: let it clear and level the ground on which its own immortal structure shall be raised. Let it, like the Nile, flood all the country that it is destined to make fertile.”
—Giuseppe Mazzini (1805–1872)
“I am renewed by death, thought of my death,
The dry scent of a dying garden in September,
The wind fanning the ash of a low fire.
What I love is near at hand,
Always, in earth and air.”
—Theodore Roethke (1908–1963)
“It is a noble land that God has given us: a land that can feed and clothe the world; a land whose coastlines would enclose half the countries of Europe; a land set like a sentinel between the two imperial oceans of the globe.”
—Albert J. Beveridge (1862–1927)