hot spot volcanism all of the mountains in this map of the floor of the pacific ocean are volcanoes...

Hot Spot VolcanismAll of the mountains in this map of the floor of the Pacific Ocean are volcanoes

Note that there are several long chains of volcanoes

But there are also many individual volcanoes

None of these volcanoes are formed along plate boundaries

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Hot Spot Volcanism

These isolated areas of volcanic activity are not associated with plate boundaries

These volcanoes are found both on continents and out in the ocean

Hot Spot Volcanism

A plume of hot mantle material rises up to the bottom of the lithosphere

Melting occurs and magma is created

These are called “hot spots”

They can last for many millions of years

Hot Spot Volcanism

The magma works its way to the surface over the hot spot and a volcano is formed

Out in the ocean, the volcano may or may not reach the surface and form an island

In fact, few oceanic volcanoes reach the surface

Hot Spot Volcanism

As the moving plate carries the volcano away from the hot spot, the volcano dies out

With time, another volcano may form

This cycle may repeat many times, forming a long chain of under sea volcanoes and islands

Hot Spot VolcanismThe Cortes Bank Seamount, 100 miles offshore of San Diego, is a 17-mile long remnant of a undersea volcanic mountain range that rises to within 3 feet of the surface

Hot Spot VolcanismFisherman and scuba divers knew about it, but it was not on any nautical maps

The U.S. Navy found it the hard way in 1985 with the aircraft carrier Enterprise

Hot Spot Volcanism“To get the biggest waves at Cortes Bank, you need light winds, low tides, and big storm swells from the northwest all at the same time, a Pacific surfer's version of the ‘perfect storm’.”

The Hawaiian Islands are the classic example of hot spot volcanism

Hot Spot Volcanism

Hot Spot VolcanismEvery island in the Hawaiian Island chain was created by volcanic eruptions that occurred as the Pacific Oceanic Plate crossed over a hot spot

Hot Spot VolcanismIn fact, the 7 main Hawaiian Islands are just the southern most portion of two great undersea mountain ranges, composed of hundreds of volcanoes, that runs for 6000 kilometers (4000 miles) across the floor of the Pacific Ocean

Hot Spot Volcanism

The plate has moved to the northwest for more than 65 million years

The big island of Hawaii is now over the hot spot

The volcanoes that formed the Hawaiian islands are classified as shield volcanoes

Hot Spot Volcanism

Hot Spot VolcanismShield volcanoes are characterized by broad, gentle slopes built up from repeated basaltic lava flows

Hot Spot VolcanismNot all eruption create big islands

Molokini represents one eruption that is slowly being reclaimed by the sea

Hot Spot VolcanismLoihi Volcano, the youngest volcano of the Hawaiian Island Chain, lies about 20 km off the south coast of the Big Island

Currently it rises 3500 meters above the surrounding sea floor and its summit is about 1000 meters beneath the surface