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:
“Wynken, Blynken, and Nod one night
Sailed off in a wooden shoe—
Sailed on a river of crystal light,
Into a sea of dew.”
—Eugene Field (1850–1895)
“Children’s view of the world and their capacity to understand keep expanding as they mature, and they need to ask the same questions over and over, fitting the information into their new level of understanding.”
—Joanna Cole (20th century)
“Then I had only prisoners’ thoughts. I awaited the daily walk which I took in the yard, or my lawyer’s visit. I managed the remainder of my time very well. I have often thought that if I was made to live in a dry tree trunk, without any other occupation but to watch the flower of the sky above my head, I would have gradually gotten used to it.”
—Albert Camus (1913–1960)
“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)