A paleoshoreline (ancient

shoreline A shore or a shoreline is the fringe of land at the edge of a large body of water, such as an ocean, sea, or lake. In physical oceanography, a shore is the wider fringe that is geologically modified by the action of the body of water past a ...

) is a shoreline which existed in the geologic past. (''Paleo'' is from an ancient Greek word meaning "old" or "ancient".) A

perched coastline A perched coastline is a fossil coastline 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 period, climates were si ...

is an ancient (fossil) shoreline positioned above the present shoreline.

Tide Tides are the rise and fall of sea levels caused by the combined effects of the gravity, gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide t ...

s cause the ocean to advance and recede in a very short time scale, in most places about twice per day; weather conditions can also cause short-term variations. Coastlines can also move due to coastal erosion, without a change in sea level. But "

sea level 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 ...

" refers to the average level over a relatively long period (years). This average sea level can advance and recede over much longer periods (thousands or millions of years), causing paleoshorelines which may be difficult to identify. Just off the coast of parts of

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

, in the last 15,000 years sea level has varied from over below, to as high as above its present level. That entire time, humans have lived in North America. A

lake A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...

may also have a paleoshoreline. Paleoshorelines have also been inferred on

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury (planet), Mercury. In the English language, Mars is named for the Mars (mythology), Roman god of war. Mars is a terr ...

; see Burgsvik Beds and

Martian dichotomy The most conspicuous feature of Mars is a sharp contrast, known as the Martian dichotomy, between the Southern and the Northern hemispheres. The two hemispheres' geography differ in elevation by 1 to 3 km. The average thickness of the Marti ...

Scientific importance

Paleoshorelines capture valuable records of

environmental change Environmental change is a change or disturbance of the environment most often caused by human influences and natural ecological processes. Environmental changes include various factors, such as natural disasters, human interferences, or animal in ...

and can tell us about modern shelf

ecosystems An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

. These structures can indicate distributions of

seabed The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

features that are habitats of

marine life Marine life, sea life, or ocean life is the plants, animals and other organisms that live in the salt water of seas or oceans, or the brackish water of coastal estuaries. At a fundamental level, marine life affects the nature of the planet. M ...

; they may also reveal the location of coastal resources once used by humans, of

archaeological Archaeology or archeology is the scientific study of human activity through the recovery and analysis of material culture. The archaeological record consists of artifacts, architecture, biofacts or ecofacts, sites, and cultural landscap ...

significance.

Examples

* The

Bering Land Bridge Beringia is defined today as the land and maritime area bounded on the west by the Lena River in Russia; on the east by the Mackenzie River in Canada; on the north by 72 degrees north latitude in the Chukchi Sea; and on the south by the tip of ...

once stood above water, and the commonest explanation of early human presence in the Americas is that the Native Americans came over this land bridge. Now it is under water. * Once

Doggerland Doggerland was an area of land, now submerged beneath the North Sea, that connected Britain to continental Europe. It was flooded by rising sea levels around 6500–6200 BCE. The flooded land is known as the Dogger Littoral. Geological sur ...

, an area of the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

, stood above water, connecting

Great Britain Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It is ...

to the rest of

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

. * In a sudden event, the

1700 Cascadia earthquake The 1700 Cascadia earthquake occurred along the Cascadia subduction zone on January 26, 1700, with an estimated moment magnitude of 8.7–9.2. The megathrust earthquake involved the Juan de Fuca Plate from mid-Vancouver Island, south along the P ...

caused the coastline of what are now

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...

and north

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

to "drop several feet". * In Asia, the

Yonaguni Monument The , also known as , is a submerged rock formation off the coast of Yonaguni, the southernmost of the Ryukyu Islands, in Japan. It lies approximately a hundred kilometres east of Taiwan. Marine geologist Masaaki Kimura claims that the formati ...

, a submerged rock formation near the

Ryukyu Islands The , also known as the or the , are a chain of Japanese islands that stretch southwest from Kyushu to Taiwan: the Ōsumi, Tokara, Amami, Okinawa, and Sakishima Islands (further divided into the Miyako and Yaeyama Islands), with Yonaguni ...

, once stood above sea level; whether the formations are human-made is still argued.

References

External links and references

Paleoshoreline research

Paleoshoerlines of Pacific islands

Paleoshorelines off Australia

Shelf sand supply determined by glacial-age sea-level modes, submerged coastlines and wave climate

Paleoshorelines off Tonga

Paleoshoreline evidence for postglacial tilting in Southern Manitoba

Submerged Shorelines in the Southern California Borderland

Physical geography Physical geography (also known as physiography) is one of the three main branches of geography. Physical geography is the branch of natural science which deals with the processes and patterns in the natural environment such as the atmosphere, h ...

Bodies of water A body of water or waterbody (often spelled water body) is any significant accumulation of water on the surface of Earth or another planet. The term most often refers to oceans, seas, and lakes, but it includes smaller pools of water such as p ...

{{palaeogeography-stub Paleogeography

Scientific importance

Examples

See also

References

External links and references