How do hot spots and the plate tectonics theory account for the fact that the hawaiian islands vary in age?

The islands are built over one hot spot, but the Pacific Plate is moving over the hot spot, taking the islands in a northwesterly direction. As the islands travel, they move farther away from their source of magma/lava and gradually become extinct. Meanwhile, erosion of wind and water has begun to wear them down. Instead of growing bigger, they are now growing smaller.

The largest, youngest, smoothest, and most active volcanoes in the chain are towards the southeast end, where the youngest of them all, Loihi is forming under the ocean. The smallest, oldest, most wrinkled (from the erosion of streams and waterfalls), extinct volcanoes are towards the northwest end. The farther Northwest you get, the smaller and older the islands are.

The island of Maui (second largest in the chain) is made up of two volcanoes. The East Maui Volcano is huge: more than 30 miles across. Its summit at Haleakala is more than 10,000 feet above sea level. It is relatively smooth, with some minor erosion. It is dormant, meaning it is not erupting now, but it could erupt again. It has erupted about ten times in the last thousand years.

The West Maui Mountains, on the other side of the island, come from an extinct volcano, are heavily eroded, and a little bit shorter--only about 8,000 feet. All of the other active and dormant volcanoes in the Hawaiian chain are to the east of Haleakala. All of the volcanoes to the north and west of Haleakala are extinct.

In fact, many of the Hawaiian islands have been eroded down to below the surface of the ocean, making them "seamounts" rather than islands. The Emperor Seamounts run almost due north to the Aleutian Trench from the end of the Hawaiian chain, suggesting an abrupt change in the direction the Pacific Plate was travelling, about 43 million years ago.

The end of the cycle comes as the oldest of the Emperor Seamounts get "swept into" the Aleutian Trench south of Alaska as the oceanic crust is subducted under the continental crust. It is this tectonic action that makes Alaska sesmically and volcanically active. In fact, an earthquake caused by this movement in 1960 triggered a tsunami which travelled across the ocean and smacked Hilo, Hawaii with tragic consequences.

From the geological record, we know that there have been times way back in prehistory where huge tsunamis from large chunks of the Hawaiian Islands falling into the ocean (the Nuuanu Slide, the Wailau Slide), have probably smacked Alaska as well. These slides did not happen because the volcanoes were "lopsided". The East Molokai Volcano, for one, was much more symmetrical before the Wailau Slide. The strongest current theory is that these slides happen because of a combination of active volcanic activity and heavy rainfall.

If the Hilina Slump (on the most active side of Hawaii, the Big Island) falls into the ocean, it should also create a devastating tsunami.

Get your lazy bombom out of the internet and go write your paper.....

they were all formed by the same hot spot --- the plate upon which they set is moving ( so the islands have been formed by major eruptions at different times by one source - through weak points in the plate - because the hot spot being below the plate does not move ) little known fact to worry about - because of this the islands are somewhat lopsided and each has had a large portion break off and form large tsunamis - Hawaii is next //// as for Jimbo's answer ALL of the islands are volcanic ( some have eroded to below sea level ) and Hawaii is the tallest mountain on earth ( counting the undersea part ) so if the plate upon which it sets ever came to the surface it would be the greatest cataclysm you could imagine ( impossible of course - or is it ? )

The islands are in a line, oldest to youngest. As the plate moves across a stationary hotspot, eruptions through the crust formed them at different times.

This has happened because as the plates move together, different underwater volcanoes have erupted at different times, and different sections of the plates has been forced up to the surface. This means that the volcanic islands have probably been above sea level for longer that the non-volcanic islands, but the non-volcanic islands contain older rock specimins.
Also, in an area of high volcanic activity, rocks are recycled faster and more often, so some metamorphic and igneous rocks may be much newer (relatively) than the surrounding rocks. Look for volcanic activity!

Good answers on this one, I'm impressed. The islands have all been formed by the same plume. As the tectonic plate moves, so does the plume, eventually creating a new land structure.

The Pacific plate, the part of the Earth's crust on which the Hawaiian islands are situated, has moved over a hot spot, where hot mantle material is convecting upwards. So the volcanoes which make up the Hawaiian islands were pushed up one after the other. Their age decreases as you go along the chain.