A perched coastline is a

fossil coastline A paleoshoreline (ancient shoreline) is a shoreline which existed in the geologic past. (''Paleo'' is from an ancient Greek word meaning "old" or "ancient".) A perched coastline is an ancient (fossil) shoreline positioned above the present shor ...

currently above the present coastline. It can be produced by one of two factors: * Higher sea levels in the past than today. For example, during the last ice age

interglacial An interglacial period (or alternatively interglacial, interglaciation) is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age. The current Holocene in ...

period, climates were significantly warmer than today, and

thermal expansion Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature, usually not including phase transitions. Temperature is a monotonic function of the average molecular kinetic ...

of the oceans, together with increased melting of

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...

s, meant that

sea levels Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datuma standardised g ...

were higher than they are today. This has created evidence of perched coastlines all around the world. * Through coastal uplift from local geological processes, particularly along the edges of

rift valley A rift valley is a linear shaped lowland between several highlands or mountain ranges created by the action of a geologic rift. Rifts are formed as a result of the pulling apart of the lithosphere due to extensional tectonics. The linear dep ...

s or

subduction zone Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

s of

tectonic plate Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large te ...

s. This second kind of perched coastline is important archaeologically, as it can expose human remains that would otherwise be below sea level.

See also