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:
“the sea is circled and sways
peacefully upon its plantlike stem”
—William Carlos Williams (1883–1963)
“Your mock saint who stands in a niche is not a woman if she have not suffered, still less a woman if she have not sinned. Fall at the feet of your idol as you wish, but drag her down to your level after that—the only level she should ever reach, that of your heart.”
—Emmuska, Baroness Orczy (1865–1947)
“I knew very well that this hope was chimerical. I was like a pauper who mingles fewer tears with his dry bread if he tells himself that at any moment a stranger will bequeath to him his fortune. We must all, in order to make reality more tolerable, keep alive in us a few little follies.”
—Marcel Proust (1871–1922)
“The land of faery
Where nobody gets old and godly and grave,
Where nobody gets old and crafty and wise,
Where nobody gets old and bitter of tongue.”
—William Butler Yeats (1865–1939)