Back to School at FamilyEducation.com

ISLANDS

Islands are land masses entirely surrounded by water. They are found in oceans, seas, rivers, and lakes. Islands vary in size from tiny rock outcrops to vast areas such as Greenland, which covers 2.2 million sq km (840,000 sq miles). There are two main types of island: oceanic islands which are remote from land; and continental islands, which often lie close to the mainland. Many oceanic islands are volcanoes. Continental islands are often formed by changes in sea level.

CONTINENTAL ISLANDS

Continental islands, such as the British Isles, rise from the shallow waters of continental shelves, which fringe the world’s continents. Often these islands were once part of the mainland, but were cut off when sea levels rose to flood the land in between. Smaller islands, called barrier islands, sometimes form off coasts where ocean currents or rivers deposit sand or mud.

CORAL ISLANDS

Coral islands, such as the Maldives in the Indian Ocean, are composed of the limey skeletons of coral polyps. Large colonies of these anemone-like creatures thrive in the warm, shallow waters off tropical coasts or around seamounts. The polyps’ soft bodies are protected by cup-shaped shells, which grow on top of one another to form rocky reefs that eventually break the surface. If the seamount subsides, just a ring of coral, called an atoll, may be left.

ISLAND CHAINS AND HOT SPOTS

Chains of volcanic islands sometimes form near the centre of tectonic plates, in zones called hot spots. Some scientists believe that hot spots occur where magma plumes surge up from the mantle below. The magma bursts through a weak point in the crust to form an island. Over millions of years, the hot spot stays in the same place as the crustal plate drifts over it, forming new islands.

ISLAND ARCS

Oceanic islands are often formed by volcanic eruptions when plates collide. As one plate is forced below another, its crust melts in the red-hot mantle below. This molten rock rises up again to burn through the crust and erupt on the sea floor. Over time, the erupted rock forms a tall seamount and eventually breaks the surface as an island.

Copyright © 2007 Dorling Kindersley

stay connected

Sign up for our free email newsletters and receive the latest advice and information on all things parenting.

Enter your email address to sign up or manage your account.

Facebook icon Twitter icon Follow Us on Pinterest

editor’s picks

highlights

Handwriting Headquarters
We've got handwriting practice worksheets, handwriting tips, and answers to your child's writing struggles, just in time for back to school. Brought to you by BIC.

11 Coolest Lunch Boxes for Kids
Send your child's lunch to school in style! Check out our picks for the 11 best lunch boxes with great features from BPA-free accessories to spill-resistant fabric.

7 Important Back-to-School Safety Tips
Follow these back-to-school safety tips to make sure your child stays safe on the way to school, in the classroom, and while on the playground.

Kindergarten Readiness App Wins Gold
Our Kindergarten Readiness app won the Gold Award of Excellence in the educational category at the 2014 Communicator Awards. This valuable checklist comes with games and activities to help your child practice the essential skills she needs for kindergarten. Download the Kindergarten Readiness app today!

Join BIC on our mission to save handwriting and Fight For Your Write! Writing helps kids become better readers, boosts their confidence and sparks their creativity. Visit BICFightForYourWrite.com to sign our petition to save handwriting!