Islands, Capes, and Peninsulas

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Islands, Capes, and Peninsulas

Islands, capes, and peninsulas are bodies of land that are partially or totally surrounded by water. They vary in size, but inevitably are prominent landmasses.


A cape is any land that extends out into water, especially a promontory (a narrow piece of land that extends from the coastline into the open water) that is significant for navigation. Some famous capes around the world are the Cape of Good Hope, a mountainous promontory south of Cape Town, South Africa, and near the southern point of Africa; Cape Morris Jesup in Greenland, the world's northernmost point of land (excluding the north polar ice cap); and Cape Cod, a sandy landmass in southeastern Massachusetts that forms a wide curve enclosing Cape Cod Bay.

Cape Cod.

Areas that contain capes traditionally attract people because of their proximity to open water, while helping to isolate residents from inland areas. The tendency for overpopulation, coupled with the isolated nature of a cape and proximity to oceans, often leads to problems in finding sources of fresh water and for the adequate disposal of wastes. Coordinated planning and management often is needed to guide development.

For example, the Cape Cod Commission was created in 1990 by an act of the Massachusetts General Court. As a result of intense growth in the 1980s, the Commission found that the region was at risk of uncoordinated or inappropriate use because of its unique coastal attractions and resources. The Commission was established as a regional planning and regulatory agency to design and implement a regional land-use plan policy for all of the Cape Cod area.

When surveyed, the majority of Cape Cod residents stated that they wanted the Cape Cod Commission to protect groundwater; encourage only clean, light industries, cultural facilities, and neighborhood businesses; protect homes from the fragile coastal environment; and restrict development that would harm the Cape. They realized that unplanned growth had brought traffic jams, mounting sewage and water quality problems, and congestion of a previously rural area. All were seen as ecological warnings that a strong regional planning effort was necessary for Cape Cod.


The distinction between an island and a continent is based somewhat arbitrarily on the relative size of the landmass. An island is any comparatively small body of land completely surrounded by water. The largest island is Greenland (see sidebar), known locally as Kalaallit Nunaat, located in the North Atlantic Ocean near Canada. It is a territory of the Kingdom of Denmark, but has locally governed itself since 1979. In comparison, the smallest continent is Australia, with an area roughly 3.5 times the size of Greenland. Even though Australia is surrounded by the ocean, is not considered an island.

Islands can occur in groups or chains. An archipelago is a chain of islands that are close to one another. The Aleutian Islands of Alaska and the Hawaiian Islands are both archipelagos. The Philippines are composed of 7,100 islands, about 1,000 of which are inhabited, and 2,500 of which remain unnamed. The city of Venice, Italy is built on 118 small alluvial islands. Between these islands run about 150 canals, which are crossed by more than 400 bridges.

Island Formation.

Islands form in a number of ways. When sea levels rise, as they have at the conclusion of each of the ice ages , islands may be created as previous coastal highlands are separated by the rising water. Such islands are found off the coasts of Maine, Scotland, and Norway. The subsidence, or sinking, of land may separate landmasses, such as in the British Isles, Sicily, and Japan. Islands may be formed at the mouths of large rivers during the formation of deltas .

Islands in deeper oceans are formed by the emergence of the peaks of submarine volcanoes, which are sometimes increased in size by continued volcanic eruptions, or by deposits of coral , or both. The original island may sink beneath the surface as the result of lithospheric plate movement, so that the entire visible structure is composed of coral. Nearly all deeper oceanic islands comprise volcanic rocks: for example, the Solomon Islands, the islands of Micronesia and Polynesia, the Azores, the Aleutians, Midway Island, Ascension Island, Tristan Da Cunha, and the Hawaiian Islands. From a geologic perspective, these islands are relatively young (less than 50 million years).

Many of the larger islands, in contrast, have a more diverse geologic makeup consisting of sedimentary and metamorphic rocks as well as volcanic: for example, Greenland, Great Britain, New Zealand, and Honshu. These larger islands often contain much older rocks: Greenland, for example, contains some of the oldest rocks on Earth.


A peninsula is a strip of land largely surrounded by water and connected to a larger landmass by a narrow isthmus. The term "peninsula" is from the Latin words for "almost island." Most of the state of Florida is a peninsula, as is most of the country of Italy. Bounded on the west by the Tyrrhenian Sea, on the east by the Adriatic Sea, and on the south by the Mediterranean Sea, Italy is a major economic force on the European continent, no doubt in part because it has coasts on three of its four sides.

Isthmus of Panama.

The Isthmus of Panama, another famous peninsula, is a narrow strip of land linking Central and South America and comprising the Republic of Panama. It is bounded on the north by the Caribbean Sea and Costa Rica, and on the south by the Gulf of Panama, the Pacific Ocean, and Colombia.

The formation of the Isthmus of Panama around 3.5 million years ago dramatically changed the evolution of marine animals. Before the isthmus was formed, Central and South America were not connected, allowing the waters of the Caribbean Sea and the Pacific Ocean to intermix.

When the Isthmus of Panama formed, it blocked that flow of ocean currents and affected the organisms that inhabited both isthmus sides. For instance, the size of the corbulid bivalve mollusks in the Caribbean is half the size of those in the Pacific. When the isthmus formed, the population was separated into two. Researchers believe that the size difference is related to the loss of nutrient-rich Pacific water flowing into the Caribbean. Research is continuing to assess what other groups of animals were affected by the Isthmus of Panama's formation.

see also Bays, Gulfs, and Straits; Canals; Corals and Coral Reefs; Land-Use Planning; Marginal Seas; Mid-Ocean Ridges; Plate Tectonics.

William Arthur Atkins


March, William M. Environmental Geography: Science, Land Use, and Earth Systems, 2nd ed. New York: John Wiley & Sons, 2002.

Strahler, Alan H. Introducing Physical Geography, 3rd ed. New York: John Wiley & Sons, 2003.

Internet Resources

Greenland. Central Intelligence Agency. <>.

Island Formation. <>.

Top Ten Largest Islands. Province of Prince Edward Island, Canada. <>.

Welcome to the Web Site of the Cape Cod Commission. Cape Cod Commission <>.

The ten largest islands in the world are as follows. Areal extent is given in square kilometers (km2) and square miles (mi2).
Greenland2,176,000 km2
840,000 mi2;
New Guinea (Asia)800,300
Borneo (Asia)743,300
Madagascar (Africa)586,600
Baffin Island (Canada)507,500
Sumatra (Indonesia)473,600
Honshu (Japan)231,000
Great Britain (United Kingdom)230,000
Victoria Island (Canada)217,300
Ellesmere Island (Canada)196,200