Rowley Shoals

An eighty-mile beach, pristine reefs, and Australia’s oil field

I. Map boundaries: 10 to 20 degrees South; 112 to 120 degrees East

II. Countries (Provinces): Australia (Western Australia), Indonesia (East Nusa Tenggara [Southeast Islands]).

III. Overview

The Indian Ocean that dominates this map area marks the transition between the equatorial forests to the north and the desert to the south. Upper surface layers of the ocean are occupied by Indonesian throughflow waters, which are warm and of low salinity. These waters flow toward the poles because the lower density causes a difference in sea level height between the Pacific and Indian Oceans.

In between is the Rowley Shoals, a chain of three diverse coral reefs and islands preserved as marine protected areas. To the north of Rowley Shoals, marine canyons associated with upwellings enhance biological productivity and attract predatory fish, sharks, toothed whales, and dolphins. To the west of the Rowley Shoals is the Exmouth Plateau, a now-submerged leftover fragment from continental drift which is attached to western Australia. The plateau is 500 to 5,000 m in depth and is dotted with pinnacles. The extensive shallow continental shelf off of Western Australia shows enhanced fish diversity. Of the 500 fish species, 76 are endemic to Australia. Rowley Shelf is the location of Australia’s largest oil field, the North West Shelf Venture. A pipeline takes the oil to shore from the vicinity of Rankin Shoal. Continue reading

Clarion, Roca Partida, and Shimata

Galapagos of Mexico; hot spot volcanoes on the sea floor

I. Map boundaries: 10 to 20 degrees North; 112 to 120 degrees West

II. Country (State): Mexico (Colima)

III. Overview

Isolated islands are noted for endemic plants and animals. The four Revillagigedo Islands formed on the East Pacific Rise or just to the west of the plate boundary between the Pacific and Rivera plates. Clarion Island, shown on this map, is 700 km southwest of the tip of Baja Peninsula and 1,000 km west of the state of Colima in Mexico. On Clarion, 14 of the 16 bird species are endemic, and there are an endemic lizard and snake. Approximately 26 percent of the plants are endemic. This endemism has earned the Revillagigedo Island chain the nickname of the Galapagos of Mexico. The rich marine fauna has been protected by the establishment of a nature reserve, but several articles not illegal fishing, and introduced sheep, pig, and rabbit, all of which compete with endemic flora and fauna, are the subject of control efforts.

To the east of Clarion is Roca Partida, or Broken Rock, which is essentially a sea stack sticking out of the Pacific Ocean. No vegetation is present, but the rock is used by nesting seabirds. To the southwest of Clarion is Shimata Seamount, which does not surface. It is believed to be a hotspot volcano of a geologically young age (The seafloor from which it rises is less than 20 million years old). Continue reading

Hundred Islands, Macclesfield, and Palawan

Giant clams and an underground river

I. Map boundaries: 10 to 20 degrees North; 112 to 120 degrees East

II. Countries: Paracel Islands and Macclesfield Bank (occupied by China), Philippines (Palawan, Pangasinan, and Zambales), and Spratley Islands (China, Philippines, Taiwan, and Vietnam occupy islands in this map area).

III. Overview

In the Lingayan Gulf off of the Philippine province of Pangasinan, fish and shrimp pens fill shallow tidal areas that once housed mangroves. Because mangroves can process fertilizers and nutrients, an integrated aquaculture could be developed that allows both mangroves and shrimp pens to coexist. Mangroves, seagrass beds, and coral reefs bordering the 7150 Philippine islands contribute to the livelihood and well-being of coastal communities by supporting fish, shellfish, shrimp while providing coastal protecting, erosion control, and nutrient recycling. The Philippines has ‘greenbelt’ laws that require a mangrove strip of 50 to 100 m facing the open sea (Primavera 2005). On the west side of the same gulf is the Hundred Islands National Park, a scenic area with hundreds of small islands shaped like mushrooms. The area is noted for its giant clams, which are the subject of research at Bolinao Marine Laboratory. The gulf was the site of World War II battles. Continue reading


Map of the Month: Rodriques, Cargados Carajos, and Agalega

Map boundaries: 10 to 20 degrees South; 56 to 64 degrees East

Country: Mauritius


The southern part of the Mascarene Plateau, the largest submerged bank in the world, is covered with seagrass and interspersed with coral reefs. The plateau extends from north to south roughly along the 60th meridian, and is mostly underwater. Mauritius, home of the dodo, and associated islets are on the southern part of this plateau. North from Mauritius are the shallow banks of the Mascarene Plateau, extending for 1000 miles to the north. From south to north, the shallower parts of the plateau are known as Soudan Banks, Cargados Carajos Shoals, Nazareth Banks, and Saya de Malha. Saya de Malha was an island until the last ice age. Its shallowest point is 8 meters deep.

The islands near Mauritius include Round Island, Flat Island, Gabriel Island, Gunner’s Quoin, Pigeon Rock, and Serpent Island. These islands are notable for bird life such as tropicbirds, puffins, and petrels; as well as rare reptiles. Round Island contains the sole relict of the palm savanna vegetation of Mauritius, as well as large numbers of seabirds. Continue reading

Leeward and Windward Islands

Map of the Month: Leeward and Windward Islands
Map boundaries: 10 to 20 degrees North; 56 to 64 degrees West
Countries: Antigua and Barbuda, Barbados, Dominica, France (Guadeloupe, Martinique, St. Barthelemy, St. Martin), Grenada, Netherlands (Saba, Sint Maartin, Sint Eustatius), St. Kitts and Nevis, St. Lucia, St. Vincent and the Grenadines, Trinidad and Tobago, United Kingdom (Anguilla, Montserrat), Venezuela (Delta Amacura, Federal Dependencies, Monagas, Sucre, Nueva Esparta)

The subduction of the South American and North American plates underneath the Caribbean Plate has led to the development of an island arc extending north from South America. To the north, the Leeward Islands consist of a western mountainous volcanic arc, extending from Saba (Netherlands Antilles) south to Basse Terre (Guadeloupe). An eastern arc of islands, extending from Sombrero Island (Anguilla) south to Marie-Galante (Guadeloupe), is less mountainous and made of limestone. Major limestone-only islands are Anguilla, St. Martin, St. Barthelemy, Barbuda, Grande-Terre, Desirade, and Marie-Galante. South of the Leeward Islands are the Windward Islands, extending from Dominica to Grenada, which consist of a series of volcanoes. Barbados, Tobago, and Trinidad make up an additional line of islands extending on the South American Plate-Caribbean Plate boundary. In the southwest of the map is a small portion of the coastal range of Venezuela, the Paria and Araya peninsulas of Venezuela, and Margarita Island, a large island north of the Venezuelan coast. Continue reading

Chiquitano and Pantanal

Map of the Month: Chiquitano and Pantanal
Map boundaries: 10 to 20 degrees South; 56 to 64 degrees West
Countries: Bolivia, Brazil, and Paraguay

This map area covers the transition between the moist Amazonian forests and the drier Chaco area, a tropical dry forest. To the northwest and north, the Amazon rain forests reach their southernmost extent and grade into drier, more seasonal forests. On the southwestern edge of the map, the edge of the Andes contain tropical moist forests and tropical dry forests. To the east are the Chiquitano dry forests of Santa Cruz and Mato Grosso and the Cerrado, a savanna-shrubland mosaic that extends in isolated outcrops from Beni and Santa Cruz across Mato Grosso and a large area of southern Brazil. On the southeast is the largest wetland in the neotropics, the Pantanal, which is increasingly known as a destination for ecotourism. Continue reading

Jiddat al-Harasis and Kuria Muria Islands

Map of the Month: Jiddat al Harasis; Kuria Muria Islands
Map boundaries: 10 to 20 degrees North; 56 to 64 degrees East
Country: Oman (Al Wusta and Dhofar regions)

The majority of this map area encompasses the tropical waters of the Arabian Sea. In the south part of the map is the triple junction of the Arabian, Indian, and Somali Plates. However, the small area of land includes the Jiddat al Harasis, a flat limestone plateau with karst features, and the Kuria Muria Islands, offshore islands noted for seabird nesting. Between Jiddat al-Harasis and the ocean is the 100-meter Al-Huqf escarpment and the 300-m in height Janabah Hills (UNEP, 2008). The coastal fog deserts are the notable ecological feature. Formed by cool offshore waters, dense seasonal fogs and dews support a unique desert ecosystem with endemic flora. The fog reaches far inland and supports an open acacia woodland. Further inland are the deserts of the Arabian Peninsula. Continue reading

Rodrigues Triple Point

Following the Turks and Caicos, the next map in this tour of subtropical areas would be between 20 and 30 degrees South and 63 and 72 degrees East. There is no land or shallow marine area within these coordinates. The sea floor at this location is where the Somali Plate, Capricorn Plate, and Antarctic Plate join. The plate boundary between the Capricorn and Somali plates is the Mid-Indian Ridge, while the boundary between the Somali and Antarctic is the Southwest Indian Ridge.
Next series: 10 to 20 degrees; 60 degrees. This includes portions of Oman, Mauritius, Bolivia, and the eastern Caribbean.