Volcanic island chains are linear series of volcanic islands thought to occurs as a result of intermittent volcanism erupting on the surface of the lithosphere as the plate moves over a mantle plume acting as a melt supply. Ocean island igneous rocks have a typical composition known as Ocean Island Basalt which differs from the normal Mid Ocean Ridge Basalt by its light and heavy earth element contents. The processes of how these changes occur are beyond the scope of this website, but are easily researched.

Ocean islands go through a typical evolutionary pattern from prominent large masses with active volcanism rising above the sea surface through reef fringed shallow envrionments to submerged guyots. This evolution is covered by Stuart Fodyce's research topic titled "Pacific Island Atoll evolution and destruction"

Guyot evolution (San Diego College)

Hawaii

Hawaii is the best known island chain starting out in central Pacific trending north-west via a series of smaller islands the island chain then joins onto the Emperor seamounts trending NNW.

Hawaii was the first inspiration for the hotspot theory of intraplate ocean island basalts by Wilson (Wilson ,63) and has since been the centre of most ocean island research as it is thought to be the most active hotspot and provides a long record of island evolution.

Hawaiian volcanism

Data on Hawaii's volcanism is generally very good due to the extent and continuity of islands from which to take data. From the graphs shown it is obvious that lava eruption rates increase rapidly with proximity to the Hawaii plume (present day Kilauea) and that there is a very good fit of age of volcanism with proximity to Kilauea. The rapid increase in volcanism close to the plume supports the idea that volcanism only occurs in a narrow region and has done so throughout the history of the island chain.

 

 

 

 

 

 

 

 

 

 

What's more is that the peak volume of erupted magma has not been constant but has in fact been increasing steadily and so is now at its highest level in 80Ma ! Condie(2001) suggests this may indicate a deeper source of energy for producing melt which is still reaching the lithosphere, as opposed to for example the Louisville chain where volcanism has virtually stopped in the last few million years

Volcanic age as a function of distance from the main hotspot event. Note the strong correlation for most of the data

(Condie, 2001)

Louisville chain

The Louisville chain is also in the south Pacific, but it is fairly different in characteristics to Hawaii. There is also a problem studying Louisville as most of the seamounts are underwater which makes sample collection very difficult.

In summary the Louisville chain also displays the '43Ma bend' but it is not as sharp at the Hawaii-Emperor bend. It is thought that the mode of eruption at Louisville is more steady over time and also spread over a larger area with intermittent volcanoes appearing at different locations.

There has also been a steady decrease in volcanic output in the last 25My and no seamounts have broken the surface in the last 11 My. This may be an indicator of a smaller melt source or a shallower plume originating at one of the higher discotinuities.

<Return to top of page>