Origin of the Hawaiian Islands

Vocab Mantle Plume: The center of vertically rising convection cells. Mantle plumes form somewhere deep in the mantle, perhaps as deep as the core-mantle boundary They start as a buildup of heat.  The heated material rises because of its density The material stops rising and begins to accumulate somewhere in the asthenosphere because of similar density. magma is formed from the spreading plume through the process of partial melting. Magma makes its way to the surface due to density differences.

Hot Spot: Volcanic activity in the middle of plate. Hot spots are NOT associated with tectonic plates and are, therefore, stationary. [i.e. the plate moves over the hot spot]

Seamount: A mountain rising from the ocean seafloor that does not reach the water's surface (sea level), and is not an island Guyot: A flat-topped seamount The Hawaiian Islands are a chain of volcanic islands in the Pacific. They formed as the Pacific Plate drifted over a hot spot in the mantle. As a result of this plate movement, the islands are older as we move westward and younger as we move eastward.

The youngest and largest island is the island of Hawaii, which currently has volcanic activity. It is the farthest east of the island chain. The oldest Island is the island of Yaruaku, which has extinct volcanoes; it is so far west, it is no longer included with the main islands. Therefore, the age of the islands increases westward from 155o West toward 168o East as island size decreases because of weathering and erosion.   age increases westward and decreases eastward   Hawaii Age: ~ 500,000 Years  155.5o W Yuruaku Age: ~ 42 Million Years  168.5o E

Nihoa does not have an age listed. What could be a possible age? Island   Approximate Age (millions of years) Longitude (in degrees & minutes) Hawaii 0.5 155o 30’ W Kanum 39.0 170o E Kauai 4.7 158o 30’ W Maui 1.1 156o 15’ W Midway 18.0 177o 30’ W Molokai 1.6 157o W Necker 10.1 164o 30’ W Nihoa ? 162o W Oahu 2.5 158o W Pearl 20.1 176o W Yuruaku 42.3 168o 30’ E Nihoa does not have an age listed. What could be a possible age? The longitude is between 158W and 164W, so it should be between 2.5 and 10 million years old.

Midway does not fit the pattern of the Hawaiian islands, it’s too far south and, therefore, was not formed as a result of the hot spot.  Midway

Examine the islands as we move west Examine the islands as we move west. What happens to the size of the islands? They get smaller as we move west, away from the hot spot. The volcano is no longer active so new material is not being added. Therefore, it is eroded by the surrounding waves. East  West 

Direction of Plate movement Since the Pacific Plate is moving toward the Northwest over the hot spot, the next island is likely to form southeast of Hawaii. Direction of Plate movement  Midway Probable position of new island

Hawaii is thought to be a descendent of the Emperor seamount chain formed as the plate shifted towards the west, then moves north. A line drawn from the beginning of the seamount chain in the north, turns east at about Mid-way and travels through the Hawaiian islands making an ‘L’

If the plate is moving west, then north, what direction is it shifting? Clockwise!

Summary The Hawaiian Island chain has formed as a result of the Pacific Plate moving over a stationary hot spot in the mantle.