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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