How old is Hawaii? How did the Hawaiian islands form? How long ago did it happen? There are about Hawaiian islands, in a chain archipelago miles long. They were all formed by volcanoes. The oldest islands are small because they are eroded, and are on the northwest end of the chain, which formed 65 million years ago. The youngest and largest island is the Big Island of Hawaii, on the east end of the chain, and it is still forming today still enlarging as new lava pours into the ocean.
A hot spot is a plume of magma or molten rock that rises from within the Earth, reaches the surface forming underwater volcanoes which may grow tall enough to rise above the sea to form islands.
In the middle of the Pacific ocean, the Hawaiian hotspot remains stationary while the Pacific plate slowly moves overhead to the northwest as illustrated in the cartoon on the left. The area directly over the hot spot is volcanically active. The activity decreases and eventually stops as the plate moves on.
The result is the Hawaiian island chain. The island of Hawaii is commonly referred to as the Big Island.
The Big Island is over the hotspot right now, making it the youngest of the Hawaiian Islands. The illustration shows topography data for the Big Island and surrounding seafloor. As the volcanic islands erode and subside, fringing coral reefs grow.
Rejuvenated stage volcanism occurs after the volcano has moved away from the mantle hot spot. Eruptions occur in sporadic locations and may be interspersed with long periods of erosion. The fourth and final stage is rejuvenated , or renewed , volcanism. Periods of erosion may precede or be interspersed with rejuvenated stage eruptions, which contribute much less than 1 percent to the cumulative eruptive volume of a volcano. Lavas commonly erupt through reefs that form offshore as erosion progresses.
Eruptions that occur near the shoreline produce volcanic maars, and eruptions further inland form lava flows that funnel down eroded stream valleys e. Rejuvenated stage activity has low eruption rates and may occur over several million years.
Black dashed lines delineate 17 distinct landslides that occurred around the Hawaiian Islands over last several million years. Following the rejuvenated stage, a long period of erosion and subsidence eventually reduces the volcanic island to sea level. Basalt is a porous rock that easily succumbs to erosion, especially with the high amounts of rainfall in Hawaii.
Erosion processes include gradual degradation due to weathering and massive landslides that displace large parts of islands. The largest of these landslides can remove entire flanks of volcanoes — such landslide deposits or debris fields litter the sea floor around the Hawaiian Islands.
Smaller landslides, especially on the rainy, windward sides of the islands, are associated with deep erosional canyons or sea cliffs. Landslides can occur during any of the eruption stages. As the volcanoes erode and islands subside, they become coral atolls, such as those west of La Perouse Pinnacles, the westernmost and oldest subaerial remnant of a former Hawaiian island. These coral reefs begin to die as they sink below water depths with enough sunlight to keep the reef healthy.
After the reef dies, the islands continue to subside. Once they are below sea level, these flat-topped, coral-capped mounds are called "guyots. Most of these volcanoes stood thousands of feet above sea level, just as the volcanoes that make up the present-day islands do today.
Kure atoll, the northernmost coral atoll in the world, is a former volcano, and the oldest part of the Hawaiian Island Chain still above water. Diameter of the atoll is 9. Skip to main content.
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