Editing Sea level (section)

== Dry land ==
{{Refimprove section|date=January 2024}}
[[File:BadwaterSL.JPG|thumb|upright=0.85|Sea level sign seen on cliff (circled in red) at [[Badwater Basin]], [[Death Valley National Park]]]]

Several terms are used to describe the changing relationships between sea level and dry land. 
 
* "relative" means change relative to a fixed point in the sediment pile.<ref>{{cite book |editor1-last=Jackson |editor1-first=Julia A. |title=Glossary of geology |date=1997 |location=Alexandria, Virginia |publisher=American Geological Institute |isbn=0922152349 |edition=4th |chapter=Relative rise in sea level}}</ref>
* "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.<ref>{{cite book |editor1-last=Jackson |editor1-first=Julia A. |title=Glossary of geology |date=1997 |location=Alexandria, Virginia |publisher=American Geological Institute |isbn=0922152349 |edition=4th |chapter=Eustatic}}</ref>
* "steric" refers to global changes in sea level due to [[thermal expansion]] and [[salinity]] variations.<ref>{{cite book |editor1-last=Jackson |editor1-first=Julia A. |title=Glossary of geology |date=1997 |location=Alexandria, Virginia |publisher=American Geological Institute |isbn=0922152349 |edition=4th |chapter=Steric}}</ref>
* "isostatic" refers to changes in the level of the land relative to a fixed point in the earth, possibly due to thermal buoyancy or [[tectonics|tectonic]] effects, disregarding changes in the volume of water in the oceans.

The melting of [[glacier]]s at the end of [[ice age]]s results in isostatic [[post-glacial rebound]], when land rises after the weight of ice is removed. Conversely, older volcanic islands experience [[relative sea level]] rise, due to isostatic [[subsidence]] from the weight of cooling volcanos. The subsidence of land due to the withdrawal of [[groundwater]] is another isostatic cause of relative sea level rise.

On planets that lack a liquid ocean, [[planetologist]]s can calculate a "mean altitude" by averaging the heights of all points on the surface. This altitude, sometimes referred to as a "sea level" or [[zero-level elevation]], serves equivalently as a reference for the height of planetary features.