Archipelago

Click here to return to the course index

First, let's set some myth's straight here: Archipelagos are simply a cluster of islands. There's no set number that defines when it goes from a cluster to an archipelago. They have not specific defining feature that makes them go from "a group of islands" to an archipelago either. Literally, it's just a group of islands. 

Examples of archipelagos: Hawaiian Islands, the Florida Keys, Easter Island, the more than 700 islands surrounding Scotland, etc.

Second, an island is an isolated landmass surrounded by water on all sides.  I'm pointing this out to distinguish archipelagos from things like wetlands where water only a few feet deep separate the dry land in sections like small "islands" or from areas where flooding occurs and separates a section of land temporarily from the mainland.  

Where to add them to your map

Archipelagos are usually a chain or cluster of islands, meaning they are relatively close together and easily seen as a group.  Here are the main examples of how these islands are formed to help you decide where they belong on your map.

Sediment Deposits: Created when the ocean currents drag & build up a large amount of sediment until it peaks over the water's surface. The Florida Keys are a perfect example of this.

Continental Fragments: Generally due to tectonic/seismic activity, these are fragments of larger pieces of land that have separated from a major landmass. The Farallon Islands off the coast of California are an example of this.

• NOTE: These are NOT "floating" islands, they are still attached to the sea floor but a crevice or some sort of divide now exists between them & the land they were once a part of. Think of it like slicing into a cake but not removing it from the plate the rest of the cake is still on. It's still touching the plate but now with space between the slice & the rest of the cake. 

Volcanic Activity: These occur when volcanoes on the ocean floor erupt and cooling magma that builds up until it breaks the water surface to form islands.  Of course the most well known version of this is the Hawaiian Islands. 

Archipelago Shapes

Now that we have an idea of how they are formed, let's take a moment and talk about shape.  Though island clusters can appear random, a far more "believable" appearance is if you follow some basic guidelines:

Sediment: Islands created along a coastline that are NOT continental fragments are generally going to be sediment deposits. They are mostly sandy with smooth coastlines & vegetation, if any, towards the middle. They are normally flat or with very gradual elevation.

Fragmented: These are more rocky, possibly with cliffs, and often mirror the coastline of the landmass they broke away from. Vegetation would match the nearby landmass. 

Volcanic: These generally take the shape of either the tectonic plate movement, run along the fault line, or form misshapen rings of islands (usually with the main volcanic island in the center or with the volcano still underwater in the center).