Marshall Islands

The Soufriere Hills Volcano on the island of Montserrat produced a plume of volcanic ash and/or steam on 1 October 2006, part of a continuing pattern of intermittent eruptions. In this image, the island of Montserrat shows an area outlined in red - the thermal hotspot. The plume of volcanic ash blows westward over the Caribbean Sea, gradually dissipating as it moves away. No recorded eruptions of the volcano occurred before 1995, but since then, volcanic ash emissions have posed recurring health hazards for Montserrat's residents. Photo courtesy of NASA.

A view of Puerto Rico (upper left) and the isles of the Lesser Antilles. The Soufriere Hills Volcano on the island of Montserrat began emitting steam and ash on 9 February 2006. Low-level activity continued for several days. The volcano produced another plume on 20 March 2006, which is captured on this image. The volcano's pale beige ash plume blows westward over the Caribbean Sea. The red outline shows where the satellite detected a thermal anomaly, an area where the ground surface was significantly hotter than its surroundings. Image courtesy of NASA.

Eruptive activity of the Soufriere Hills Volcano on Montserrat is evidenced by an extensive smoke and ash plume streaming towards the west-southwest (image taken 29 October 2002). Significant eruptive activity began in 1995, forcing the authorities to evacuate about two-thirds of the island's original population of 12,000, and to close off the southern portion of the island. Image courtesy of NASA.

Majuro and Arno Atolls appear as meandering lines of delicate white against a darker ocean background in this satellite image. Areas of shallow water near the shore appear iridescent blue, especially in the southwest portion of each atoll and off the northwest tip of Arno Atoll. Overhead, tiny white clouds dot the sky. Majuro Atoll is 40 km (25 mi) in circumference, and it partially encloses a lagoon of nearly 300 sq km (115 sq mi). The lagoon is far bigger than the atoll itself, whose land area is less than 10 sq km (4 sq mi); walking from the lagoon side to the ocean side of the atoll takes only minutes. Neighboring Arno Atoll encloses three lagoons: two "pinched lagoons" in the northeast and northwest, and a main lagoon of nearly 340 sq km (130 sq mi). Arno's total land area is just 13 sq km (5 sq mi). Scientists have long understood that coral atolls develop around volcanic islands and remain there after those islands have eroded away. To what extent the final shape of an atoll is influenced by wind and ocean wave activity, however, remains a topic of debate. Image courtesy of NASA.