coastline

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coastline

geography

Also known as: shoreline

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July 22, 2026

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A coast is the broad area of land that borders the sea. The world's coastlines measure approximately 312,000 km (193,000 miles) and have shifted over geologic time due to changes in sea and land levels. During past glaciations, lower sea levels exposed large parts of the continental shelf.1

Coastal landforms are shaped by erosional processes like wave action and chemical weathering, as well as deposition of sediment by currents and tectonic activity. These processes, along with the underlying geology, determine whether a coast is characterized by steep cliffs or gentle beaches and plains. Rising sea levels, driven by melting ice caps, are a current concern, potentially leading to increased coastal flooding, storm surges, and erosion, impacting populations and ecosystems.123

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coastal landforms
Beaches
A close look at the shoreline along most beaches will show that it is not straight or gently curved but rather that it displays a regularly undulating surface much like a low-amplitude sine curve. This is seen both on the plan view of the shoreline and the topography of the…
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A close look at the shoreline along most beaches will show that it is not straight or gently curved but rather that it displays a regularly undulating surface much like a low-amplitude sine curve. This is seen both on the plan view of the shoreline and the topography of the…
Read More

gulf
Topographic characteristics
If the shoreline is irregular and has a complex geologic structure, groups of gulfs of a similar nature may occur. Most shorelines have small reentrants of various size that are called bays.
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If the shoreline is irregular and has a complex geologic structure, groups of gulfs of a similar nature may occur. Most shorelines have small reentrants of various size that are called bays.
Read More

coast
The coastlines of the world’s continents measure about 312,000 km (193,000 miles). They have undergone shifts in position over geologic time because of substantial changes in the relative levels of land and sea. Studies of glaciations during the Pleistocene Epoch (2.6 million to 11,700 years ago)…
Read More
The coastlines of the world’s continents measure about 312,000 km (193,000 miles). They have undergone shifts in position over geologic time because of substantial changes in the relative levels of land and sea. Studies of glaciations during the Pleistocene Epoch (2.6 million to 11,700 years ago)…
Read More

paleogeography
Shorelines and continental margins
In contrast to mountain ranges, which take tens to hundreds of millions of years to uplift and erode, the location of Earth’s shorelines can change rapidly. The familiar shapes that characterize today’s shorelines such as Hudson’s Bay, the Florida peninsula, or…
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In contrast to mountain ranges, which take tens to hundreds of millions of years to uplift and erode, the location of Earth’s shorelines can change rapidly. The familiar shapes that characterize today’s shorelines such as Hudson’s Bay, the Florida peninsula, or…
Read More

coastal landforms
Tides
…and the position of the shoreline.
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…and the position of the shoreline.
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