The Emerald Island is a phantom island

Phantom island

Phantom islands are islands that were believed to exist, and appeared on maps for a period of time during recorded history, but were later removed after they were proved to be nonexistent...

 reported to lie between Australia and Antarctica and south of Macquarie Island

Macquarie Island

Macquarie Island lies in the southwest corner of the Pacific Ocean, about half-way between New Zealand and Antarctica, at 54°30S, 158°57E. Politically, it has formed part of the Australian state of Tasmania since 1900 and became a Tasmanian State Reserve in 1978. In 1997 it became a world heritage...

. It was first sighted by the British sealing ship Emerald, captained by William Elliot, in December 1821, and the name of the presumed island derives from the name of this ship. It was supposed to be a small (but high or mountainous) island at 57°30′S 162°12′E.

No trace of the island was found by the 1840 United States Exploring Expedition

United States Exploring Expedition

The United States Exploring Expedition was an exploring and surveying expedition of the Pacific Ocean and surrounding lands conducted by the United States from 1838 to 1842. The original appointed commanding officer was Commodore Thomas ap Catesby Jones. The voyage was authorized by Congress in...

. Although a captain visiting Port Chalmers

Port Chalmers

Port Chalmers is a suburb and the main port of the city of Dunedin, New Zealand, with a population of 3,000. Port Chalmers lies ten kilometres inside Otago Harbour, some 15 kilometres northeast from Dunedin's city centre....

 reported seeing it sometime before 1890, a search by the Nimrod in 1909 turned up nothing. Nevertheless, it appeared on a map as late as 1987 in a desk calendar book (with atlas) published by American Express

American Express

American Express Company or AmEx, is an American multinational financial services corporation headquartered in Three World Financial Center, Manhattan, New York City, New York, United States. Founded in 1850, it is one of the 30 components of the Dow Jones Industrial Average. The company is best...

.

The abyssal plain

Abyssal plain

An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between 3000 and 6000 metres. Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth’s surface. They are among the flattest, smoothest...

on the ocean floor beneath the supposed location of this phantom island is named Emerald Basin.