definitions of Oceania included most or all of the Malay Archipelago. Definitions of Oceania which include the Malay Archipelago are much rarer today; the non-oceanic nature of the Malay Archipelago and its geological connections to Asia may not have been as widely known in the 19th century. The Philippines are the closest to the Oceania subregion of Micronesia, and are sometimes historically associated with it, mainly due to their shared Christian cultures and Spanish colonial histories, and their shared Austronesian backgrounds. Anthropologically, New Guinea is a part of Melanesia, but it is sometimes included in the Malay Archipelago. The state of Papua New Guinea is an observer in the Association of Southeast Asian Nations (ASEAN), which includes mainland states of Southeast Asia, and has contemplated full membership in this organisation. Indonesia, Malaysia, the Philippines and Singapore (as well as Japan) are all dialogue partners of the Pacific Islands Forum (PIF), and Timor-Leste are an observer. However, only countries solely associated with Oceania have full membership, such as Australia, Federated States of Micronesia, Fiji, New Zealand and Samoa. North America and Oceania and : Oceania at times is considered to encompass all oceanic islands in the Pacific Ocean. Oceanic islands are defined as islands that were never connected to a continental landmass, and which formed through volcanic acitivity in the ocean. Mexico administer the oceanic Guadalupe Island and Revillagigedo Islands, and the oceanic islet of Rocas Alijos, while Costa Rica administer the oceanic Cocos Island. All of these islands were uninhabited prior to European discovery, and none lie on the North American or South American tectonic plates; the Mexican islands lie on the Pacific Plate with most of Oceania, and Cocos Island lies on the self-named Cocos Plate, which contains no other islands besides Colombia's Malpelo Island. Furthermore, the Mexican state of Baja California, despite being physiologically connected to the American landmass, is in fact part of the Pacific Plate. Guadalupe Island and Rocas Alijos are rarely categorized with other Pacific Islands, as they are only 250 to 300 kilometers removed from Baja California. Revillagigedo's most remote island, Clarion, is 700 kilometers from Mexico's coast, and Cocos Island is 550 kilometers from Costa Rica's coast. These islands are more frequently associated with the term Pacific Islands, and occasionally have been included as part of Oceania. Remoter islands such as France's Clipperton (1,100 kilometers from Mexico's coast) are even more commonly associated