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 called
you faced the estuary,
you were drowned as the tide passed.
I am glad of this
at least you have escaped.”
—Hilda Doolittle (1886–1961)
“To punish drug takers is like a drunk striking the bleary face it sees in the mirror. Drugs will not be brought under control until society itself changes, enabling men to use them as primitive man did: welcoming the visions they provided not as fantasies, but as intimations of a different, and important, level of reality.”
—Brian Inglis (b. 1916)
“The inhabitants of the Cape generally do not complain of their “soil,” but will tell you that it is good enough for them to dry their fish on.”
—Henry David Thoreau (1817–1862)
“The unconscious is the ocean of the unsayable, of what has been expelled from the land of language, removed as a result of ancient prohibitions.”
—Italo Calvino (1923–1985)