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:
“What do the botanists know? Our lives should go between the lichen and the bark. The eye may see for the hand, but not for the mind. We are still being born, and have as yet but a dim vision of sea and land, sun, moon, and stars, and shall not see clearly till after nine days at least.”
—Henry David Thoreau (1817–1862)
“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)
“I can love both fair and brown;
Her whom abundance melts, and her whom want betrays;
Her who loves loneness best, and her who masks and plays;
Her whom the country formed, and whom the town;
Her who believes, and her who tries;
Her who still weeps with spongy eyes;
And her who is dry cork, and never cries.
I can love her, and her, and you and you,
I can love any, so she be not true.”
—John Donne (1572–1631)
“My father upon the Abbey stage, before him a raging crowd.
“This Land of Saints,” and then as the applause died out,
“Of plaster Saints;” his beautiful mischievous head thrown back.”
—William Butler Yeats (1865–1939)