Use a globe or a map of the world to point out to students that
most of Earth is covered by water;
Australia is the smallest island continent in the world;
Greenland is the worlds largest island;
Great Britain, Japan, and Australia are island nations; and
Hawaii is an island state of the United States.
Now refer to relief maps, a globe, or a world map to show students that the surface of Earth has peaks and valleys and plateaus, some covered by water and others above water.
Next, distribute copies of the Background Sheet: Three Ways to Make an Island and review with students the three major ways that islands form. Refer students to the diagrams on the activity sheet.
Point out the polar ice caps on a map of the world or a globe. Explain that during the last ice age the ice caps were larger. More of Earths water was frozen at the poles, and the oceans were shallower. Explain that sea levels rose dramatically at the end of the Ice Age as Earth warmed and the polar ice caps began to melt. When the ice melted, about 10,000 years ago, some bodies of land that had been connected to continents were cut off from the mainland and became islands. This is how the islands of New Zealand became isolated from the mainland of Australia.
Stack books on a desk to represent a mainland, a land bridge, and a body of land connected to the mainland, and have students refer to their activity sheets again. Explain that as sea levels rise, water submerges the land bridge, creating islands out of landmasses that were once connected.
Islands may also be formed by hardworking, coral-building sea organisms. Explain that among the creatures living in the seas are tiny animals called polyps. Polyps are related to jellyfish, but they live in colonies, and they protect their soft bodies by building limestone walls around them. As these colonies grow, they form reefs. Eventually, these reefs can cover hundreds of square miles. The polyps dont build their reefs above the surface of the water, but if the sea level drops or the land below the reef rises, the reef may emerge from the water. Then water-borne sand and wind-borne dust will accumulate on the reef and form an island. The Florida Keys are one example of coral reef islands.
Another way islands can form is through volcanism. Explain that volcanoes can erupt underwater as well as on land. With each eruption, lava flows build up. Over time, the volcano can grow above the surface of the sea, forming a volcanic island, such as those that make up Hawaii.
Explain that the way an island forms affects the range of species of plants and animals living on it. If the island is cut off from the mainland by rising sea level, then mainland species are likely to be living on it from the start. If the island forms as a volcano or as a coral reef, there may be no plants or animals living on it to begin with, and any species that does get established there has to have come from somewhere else. Animals can reach an island by traveling on floating objects in the ocean, such as trees, floating logs, or reeds. Plants and birds can reach an island by air.
Next, hand out copies of the Classroom Activity Sheet: Island Investigation and have students work in pairs or groups to prepare a presentation on one of the islands listed below. Students can use printed library resources or the Internet to conduct their research. Presentations should include the following:
A description of the islands location
A brief description of the islands geography
An explanation of how and when the island formed
A description of at least one animal species that is found only on the island
An explanation of how the species has adapted to life on the island
Surtsey is an island off the coast of Iceland. Referred to as the newest place on earth, it was formed by a volcanic eruption in 1963. See Sandwort, Seabirds, and Surtsey .
The Galapagos Islands are located off the coast of Ecuador and have remained geographically isolated since they were formed three or four million years ago. Information can be found online at TerraQuests Virtual Galapagos.
Inaccessible Island is located in the Tristan da Cunha group of islands in the South Atlantic. It is home to just one species of birdthe Inaccessible Island flightless rail, the smallest flightless bird in the world. See Inaccessible Island.
Madagascar, the worlds fourth-largest island, is home to some 40 species of lemur, an animal that evolved from what may have been a single pair of mammals that floated to the island 70 million years ago. Information can be found online at Madagascar.
After students have completed their presentations, summarize what they have learned about how islands form, how plants and animals come to live on islands, and how species adapt to their environment to survive. Then pass out copies of the Take-Home Activity Sheet: Island Hunting. Students should be able to answer the questions based on the classroom discussion and the student presentations.
Long Island, in the state of New York, formed from the silt deposited by a melting glacier in North America at the end of the last ice age. Challenge students to investigate islands that have formed in less familiar ways, such as Long Island and barrier islands throughout the world. Have students prepare a class demonstration about these formation methods.
Many scientists believe that burning fossil fuels causes global warming, an overall increase in the average temperature worldwide. If global warming continues, what effect do you think it will have on the worlds islands? On the plants and animals living on those islands?
Hypothesize about the effect a future ice age would have on the worlds islands and their plants and animals.
How do animals and plants travel to islands?
Small islands have far less diversity of species than large continents. How can you explain this difference in diversity?
What is the greatest danger to the delicate ecosystems of the worlds islands? What steps do you think should be taken to reduce this danger?
Imagine that a new volcanic island has formed. Choose its location and hypothesize about what types of plant and animal species you would expect to colonize the island.
You can evaluate your students presentations using the following three-point rubric:
Three points: inclusion of all required elements in the presentation; clear explanation that includes concrete facts; logical organization; few errors in grammar, usage, and mechanics
Two points: inclusion of at least two of the required elements in the presentation; clear explanation that includes concrete facts; organization that is good enough to follow; some errors in grammar, usage, and mechanics
One point: inclusion of one of the required elements in the presentation; explanation that includes concrete facts; errors in grammar, usage, and mechanics
Have individuals or groups of students choose an island and prepare a travelogue about it, including information about its formation and the plant and animal species that live on the island. The travelogue can be presented with PowerPoint, as a poster, on a Web site, on videotape, or through another medium.
On the islands of Indonesia live many species of monitor lizard. Each species has adapted to the conditions of its specific island. On one, the monitor has evolved into a gentle vegetarian, while on another it has become the Komodo dragon, the main predator on the island. Challenge students to research three species of monitor lizard and the conditions on each type of island. Have the students develop hypotheses to explain why each species adapted as it did. The following Web site from the American Museum of Natural History will get them started: http://www.amnh.org/exhibitions/endangered/ora/ora.html.
Galapagos: Islands Born of Fire
Tui De Roy. Warwick Publishing, 1998.
The author of this stunning volume was raised on the Galapagos Islands and has spent her life photographing its variety. Her extraordinary color photographs enhance the story of these unique islands, their volcanic origins, their diverse and distinctive wildlife, and their delicate ecosystems. The final chapter covers the challenges facing the Galapagos in the coming century.
Islands: Portraits of Miniature Worlds
Louise B. Young. W.H. Freeman, 1999.
Here is an opportunity to explore islands around the world, from the lush beauty of the Hawaiian islands, to the fire and ice islands of Iceland, to the mysterious Easter Island. There is even a chapter about the mythic island of Atlantis! Occasional pencil drawings help illustrate the information.
continent Definition: One of Earths major landmasses, which include North America, Africa, South America, Asia, Europe, Australia, and Antarctica. Context: An island is a body of land smaller than a continent and is completely surrounded by water.
coral reef Definition: A mound or ridge of coral skeletons and calcium deposits that forms in warm shallow seas. Context: A coral reef is a complex ecosystem that shelters many kinds of marine life.
ice age Definition: Any part of geological time during which glaciers covered large parts of Earths surface. Context: Huge sheets of ice covered Earths surface during the last ice age, called the Pleistocene glacial epoch, which ended 11,500 years ago.
sea level Definition: The surface level of the sea, especially the mean between high and low tide, which is used as a standard in calculating land elevations and sea depths. Context: As a volcano grows, it may rise above sea level and become an island.
species Definition: The most fundamental classification of living things in biology, comprising individuals that can breed with one another but not with those of other species; a subdivision of a genus. Context: An islands isolation limits the number and variety of its animal and plant species.
volcanism Definition: The force, activity, or phenomena associated with volcanoes. Context: Volcanism created the Hawaiian Islands.
volcano Definition: A mountain or hill created around a vent in Earths crust through which molten rock, ash, and gases are expelled. Context: Surtsey, the worlds youngest island, is the top of an undersea volcano.
This lesson plan may be used to address the academic standards listed below. These standards are drawn from Content Knowledge: A Compendium of Standards and Benchmarks for K-12 Education: 2nd Edition and have been provided courtesy of the Mid-continent Research for Education and Learning in Aurora, Colorado.
Grade level: 6-8 Subject area: Earth and Space Sciences Standard:
Understands Earths composition and structure. Benchmarks:
Knows how landforms are created through a combination of constructive and destructive forces (e.g., constructive forces such as crustal deformation, volcanic eruptions, and deposition of sediment; destructive forces such as weathering and erosion).
Grade level: 6-8 Subject area: Life Sciences Standard:
Understands biological evolution and the diversity of life. Benchmarks:
Knows basic ideas related to biological evolution (e.g., the diversity of species is developed through gradual processes over many generations; biological adaptations, such as changes in structure, behavior, and physiology, allow some species to enhance their reproductive success and survival in particular environments).