Table of Contents
The Origin of Islands
Islands are created by climate change and by geophysical events
Continental islands are the result of changes in sea level
Oceanic islands are formed in deep water through volcanic activity
Continental Drift
The Break-up of Pangaea
First Thoughts on Continental Drift
Evidence Supporting Continental Drift: The Shapes Match!
The Fossil Record Supports Continental Drift:
The reptile Mesosaurus swam in the fresh waters of Pangaea 260 million years ago. Today, its fossils are found in only in Africa & South America.
Fossils of the fern Glossopteris are found on South America, Africa, India, Australia & Antarctica
The earth’s surface consists of a number of plates which move relative to each other, carrying the continents with them
Islands and Plate Tectonics
When plates move apart at mid-ocean ridges there is intense underwater volcanic activity as new rock is added to the separating plates.
The result is that rocks get older as one moves away from a mid-ocean ridge.
Particularly intense activity can produce a volcano that reaches the surface to form an island
The island attaches to one of the plates and in time is carried away from the mid-ocean ridge
When plates collide one is “subducted” under the other, producing intense volcanic activity behind the subduction trench
Subduction zones may produce arcs of oceanic islands: e.g. the Aleutians
The movement of the Pacific plate across a fixed hot-spot has created the Hawaiian islands
Differences Between Continental & Oceanic Islands
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Author: Martyn L Gorman
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