volcanoes Hawaii

[lightoftruth]

why are there volcanoes on Hawaii despite is not being located on a plate margin?

[brachiopod]

It is a 'hot spot' - an upwelling of magma within the mantle that manages to penetrate the (relatively) thin oceanic crust to form a volcanic sea mount.

Where these sea mounts rise above sea level - a volcanic island will appear.

They are often found in 'chains', since, compared with the movement of the oceanic plate, these upwellings are realtively static. As the plate moves over the hot spot, new, active islands are formed, whilst those furthest away have long since passed over the hot spot will be less active or extinct.

Hawaii is just part of the long, continuous Emporor Sea Mount - Hawaiian Ridge chain that extends all the way from the Aleutian Trench - though not all sea mounts penetrate the ocean surface to form islands.

[gen2]

An excellent answer from brachiopod and I'm surprised Mr Pahoehoe didn't get a look-in on this.

The only term not used by brachiopod that may prove useful when Googling, is "mantle plume"

[brachiopod]

Aa ! My clinkery bottom! You're right, gen, I should have mentioned mantle plumes.

As for Mr. P, perhaps he's feeling a bit ropey?

[dundurn]

The term "island arc" also comes up sometimes as the plate movement is rarely in a totally straight line and the resulting chain usually curves. Whether the mount breaks the surface is a function of the rate at which magma is being extruded v the rate at which the plate is moving v the local depth of water.

[Docsteve]

Why are there volcanoes on Hawaii despite it not being on a plate margin? I haven't an answer and the answers provided whilst being correct do not say "why" the hotspot is there.

Theories as to what is happening exist. Hawaii and Yellowstone are mantle hotspots that stay in a fized position while the crust moves over the top and hence the volcanic arc progresses. The hotspot doesn't move. The real question is "why" these mantle hotspots are in these exact fixed positions.

Convection in the upper mantle and lower crust may provide much of the answer to explain what is happening but as the questions of why it occurs in mid-plate and then why it doesn't move itself as a natural consequence of convection variation this is unanswered.

I would be very interested in the answer why myself. Perhaps the models are not quite correct when they fail to answer important scenarios such as this. Perhaps we need a new theory.

[razza]

Hawaii and its islands were all formed by volcanoes,at the moment there is another new island forming,but if things stay as they are with the continuous outflow on Hawaii it will eventually become the biggest island on earth,dont think we will be around when that happens.