Lesson 2.3:Islands

*Refer to Chapter 3 in your Textbook

Learning Goals:1. I can explain how a hotspot forms an

island chain.2. I can label the structure of a barrier

island.3. I can differentiate between the 3 types of

reefs.

Hot Spots Wilson (1963) 1. Volcanoes can form in the middle of a plate

where magma rises upward until it erupts on the sea floor, at what is called a “hot spot”

2. The hotspot will stay still as the plate moves, creating a chain of islands

Hot Spots

Barrier Islands Barrier Islands form when a piece of the

mainland is broken off and separated by a body of water (lagoon)

They can be very large and can be ideal for beaches & hotels, but are also vulnerable to erosion and weather

Barrier Islands

Barrier Island Structure Ocean, Beach, Dune, Flat, Marsh, Lagoon Dune: top of the beach, usually inclining to

protect the coastline Barrier flat: thick vegetation Salt marsh: swamp

Reef FormationFringing:

Most commonForm along shoreline of coast or islandThe fore side (facing the ocean) has the most biological activity

Reef FormationBarrier:

Forms when island begins to sink or when there is a rock for the coral to grow onSeparated from land by a lagoonUsually much larger than a fringing reef

Reef FormationAtoll:

Forms when island sinks below sea levelThe remains of the island are carried away by the tectonic plate, leaving behind a circular reef