Geologically, they are the oldest in the Hawaiian-Emperor seamount chain, shaped by volcanic activity and erosion over millions of years.

[7] As the Pacific Plate moved north and later northwest over the hot spot, volcanic eruptions built up islands in a linear chain.

Nihoa, Necker, and Gardner Pinnacles are rocky, basalt islands that have not eroded enough to form an atoll, or that lack a substantial coral reef.

Kure Atoll straddles the Darwin Point, and will sink beneath the ocean when its coral reef cannot keep up with the rate of subsidence, a destiny that awaits every Hawaiian island.

From the late 19th to the early 20th centuries, fishermen, guano miners, and feather hunters killed most of the birds and sea life living in the NWHI.

The NWHI has been recognized as an Important Bird Area (IBA) by BirdLife International because of its seabirds and endemic landbirds.

Other notable species are the Laysan albatross, the highly endangered Hawaiian monk seal, and the green sea turtle.

Most endemic species are highly vulnerable to extinction as one major catastrophic event could wipe out all of the vegetation on each small island.

[15] Archeological evidence suggests ancient Hawaiians visited but did not live on Mokumanamana (Necker) and French Frigate Shoals, and the islands were deserted when Europeans arrived in the 18th century.

Mokumanamana lacks vegetation and is unsuitable for agriculture, and archeological studies indicate early Hawaiians only visited and used the island for religious purposes.

On June 15, 2006, American President George W. Bush issued a public proclamation creating Papahānaumokuākea Marine National Monument under the Antiquities Act of 1906.

The Monument encompasses the islands and surrounding waters, forming the largest marine wildlife reserve in the world.

[16][17] Entry to the Monument is limited through a permit system, jointly administered by NOAA, FWS, and the state of Hawaii.

Anyone who comes to the islands must follow stringent procedures designed to prevent any stray species from entering and disrupting the ecosystem.

However, French Frigate Shoals and Midway Atoll are exempted from these rules, as they are deemed too altered by humans already to worry about introducing new species.